CTI Journal by Digital Publisher

The CTI Journal (ISSN: 0273-3250) PUBLISHED SEMI-ANNUALLY Copyright 2013 by The Cooling Technology Institute, PO Box 73383, Houston, TX 77273. Periodicals postage paid at Houston, Texas. MISSION STATEMENT It is CTIâ&#x20AC;&#x2122;s objective to: 1) Maintain and expand a broad base membership of individuals and organizations interested in Evaporative Heat Transfer Systems (EHTS), 2) Identify and address emerging and evolving issues concerning EHTS, 3) Encourage and support educational programs in various formats to enhance the capabilities and competence of the industry to UHDOL]H WKH PD[LPXP EHQHÂżW RI (+76 4) Encourge and support cooperative research to improve EHTS TechnolRJ\ DQG HIÂżFLHQF\ IRU WKH ORQJ WHUP EHQHÂżW RI WKH HQYLURQPHQW $VVXUH acceptable minimum quality levels and performance of EHTS and their components by establishing standard speciÂżFDWLRQV JXLGHOLQHV DQG FHUWLÂżFDWLRQ programs, 6) Establish standard testing and performance analysis systems and prcedures for EHTS, 7) CommuniFDWH ZLWK DQG LQĂ&#x20AC;XHQFH JRYHUQPHQWDO entities regarding the environmentally UHVSRQVLEOH WHFKQRORJLHV EHQHÂżWV and issues associated with EHTS, and 8) Encourage and support forums and methods for exchanging technical information on EHTS. LETTERS/MANUSCRIPTS Letters to the editor and manuscripts for publication should be sent to: The Cooling Technology Institute, PO Box 73383, Houston, TX 77273. SUBSCRIPTIONS The CTI Journal is published in January and June. Complimentary subscriptions mailed to individuals in WKH 86$ /LEUDU\ VXEVFULSWLRQV yr. Subscriptions mailed to individuals RXWVLGH WKH 86$ DUH \U CHANGE OF ADDRESS Request must be received at subscripWLRQ RIÂżFH HLJKW ZHHNV EHIRUH HIIHFWLYH date. Send both old and new addresses for the change. You may fax \RXU FKDQJH WR RU HPDLO vmanser@cti.org. PUBLICATION DISCLAIMER CTI has compiled this publication with care, but CTI has not Investigated, and CTI expressly disclaims any duty to investigate, any product, service process, procedure, design, or the OLNH WKDW PD\ EH GHVFULEHG KHUHLQ The appearance of any technical data, editorial material, or advertisement in this publication does not constitute endorsement, warranty, or guarantee by CTI of any product, service process, SURFHGXUH GHVLJQ RU WKH OLNH &7, does not warranty that the information in this publication is free of errors, and CTI does not necessarily agree with any statement or opinion in this pubOLFDWLRQ 7KH HQWLUH ULVN RI WKH XVH RI any information in this publication is assumed by the user. Copyright 2014 E\ WKH &7, -RXUQDO $OO ULJKWV UHVHUYHG

Contents )HDWXUH $UWLFOHV 8

pH Impact On Inhibitor Performance Robert J Ferguson

Understanding Vibration Switches David A. Corelli

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Frank Michell, Marcela Politano and Jeff Stallings

Composite Materials Selection for Structures in Seismic Regions Andrew Green and Andrey Beyle

Lessons Learned from a High Recovery RO - Based ZLD System Brad Buecker

'HYHORSPHQW DQG $SSOLFDWLRQ RI 3KRVSKRUXV )UHH &RROLQJ :DWHU 7HFKQRORJ\ Raymond M. Post, Richard Tribble and Prasad Kalakodimi

1RLVH &RQWURO 2I :DWHU &RROLQJ 7RZHUV ,Q 5RPH V +RVSLWDO $UHD

Augusto Papa

Special Sections 61 78 86

CTI Table Tops CTI Licensed Testing Agencies &7, &HUWLÂżHG 7RZHUV CTI ToolKit

see page....8

Departments 2 2 6

Multi Agency Press Release Meeting Calendar 9LHZ )URP WKH 7RZHU Editorâ&#x20AC;&#x2122;s Corner

see page....24

see page...74

CTI Journal, Vol. 35, No. 2 see page...54

CTI Journal

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Internet Address: KWWS ZZZ FWL RUJ ( PDLO YPDQVHU#FWL RUJ

FUTURE MEETING DATES Annual Conference

Committee Workshop

February 8-12, 2015 Sheraton New Orleans, LA

July 12-15, 2015 Tradewinds Island Resort St. Pete Beach, FL

February 7-11, 2016 Hilton Houston North Houston, Texas

For Immediate Release Contact: Chairman, CTI Multi-Agency Testing Committee

Houston, Texas, 3-May-2014 The Cooling Technology Institute announces its annual invitation for interested drift testing agencies to apply for potential Licensing as CTI Drift Testing Agencies. CTI provides an independent third party drift testing program to service the industry. Interested agencies are required to declare their interest by July 1, 2014 at the CTI address listed.

CTI Journal, Vol. 35, No. 2

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CTI Journal, Vol. 35, No. 2

pH Impact On Inhibitor Performance of an inhibitor can be critical when the dissociated DQG SURWRQDWHG IRUPV KDYH VLJQLÂżFDQWO\ GLIIHUHQW HIÂżFDF\ DV LQKLELWRUV $ FRQVHUYDWLYH PHWKRG IRU employing the dissociation state is to assume that WKH GLVVRFLDWHG LQKLELWRU FRQFHQWUDWLRQ IRU WKH ÂżQDO $%675$&7 step is the active species. Water treatment chemists have long observed that Understanding the impact of pH upon the relative some scale inhibitors work better at high pH rather HIÂżFDF\ RI DQ LQKLELWRU FDQ EH NH\ WR SURYLGLQJ WKH than low pH, and that some inhibitors have little, if optimum inhibitor dosage and in assuring that the any, activity at very low pH. Examples would be minimum effective active inhibitor is present. the effectiveness of polyacrylic acid at high pH as a In the simplest case, an inhibitor may have almost calcium carbonate inhibitor, as in ash sluice and some HIÂżFDF\ LQ D S+ UDQJH ZKHUH LW LV DOPRVW mining applications, mediocre performance near a FRPSOHWHO\ GLVVRFLDWHG DQG FORVH WR HIÂżFDF\ LQ neutral pH, as in cooling water applications, and very a pH range where the inhibitor is almost completely low activity in an acid pH range, as in gypsum control Robert J Ferguson protonated. This scenario has been reported for in the pH range from 2 to 4. This paper provides a simple phosphonates such as HEDP (1-hydroxyl framework for evaluating relative inhibitor activity using dissociaHWK\OLGHQH GLSKRVSKRQLF DFLG 3URÂżOHV FRPSDULQJ WKH SURWLRQ SURÂżOHV IRU FRPPRQ LQKLELWRUV DQG FDOFXODWLQJ WKH GLVWULEXWLRQ of inhibitor species versus pH. The use of dissociation constants WRQDWLRQ VWDWH DQG LQKLELWRU HIÂżFDF\ IRU WKH VLPSOH SKRVSKRQDWHV for inhibitors provides a valuable tool for matching inhibitors to a LQGLFDWH WKDW WKH ÂżQDO GLVVRFLDWLRQ FRQVWDQW S.a) is a controlling VSHFLÂżF DSSOLFDWLRQ UDQJH S+ DQG DV DQ DLG LQ VFDOH LQKLELWRU VHOHF- factor with minor, if any, contribution from lower dissociation states. tion. It can also provide a tool for evaluating and comparing new In a more complex case, such as HDTMPA (hexamethylene diaminemolecules. The paper, and the concept of active versus inactive (or tetra(methylene phosphonic) acid), the various protonation states less active) inhibitor forms, offers explanations for what appeared DSSHDU WR KDYH VLJQLÂżFDQW HIÂżFDF\ VR WKHLU FRPELQHG HIÂżFDF\ to be anomalies during the modeling of inhibitor performance data, is greater than might be expected based upon experience with a simpler inhibitor. DQG ÂżHOG REVHUYDWLRQV VXFK DV Â&#x2021; Why is the minimum dosage requirement for calcium *ULIÂżWKV HW DO GHYHORSHG GLVVRFLDWLRQ SURÂżOHV IRU FRPPRQ SKRVphosphate inhibition by some polymers so much lower phonates and compared them to inhibition studies over the same pH range. They summarized their laboratory results for simple than the requirement for others? Â&#x2021; Why does the addition of pH as a variable for correlation SKRVSKRQDWHV DV IROORZV GUDPDWLFDOO\ LPSURYH WKH FRUUHODWLRQ FRHIÂżFLHQW QLFHQHVV â&#x20AC;&#x153;The general trend â&#x20AC;Ś is an improvement in performance with inRI ÂżW IRU VRPH LQKLELWRUV HYHQ IRU VFDOHV ZKRVH VROXELOLW\ creasing pH. The improvement runs parallel to the titration curve with full activity occurring only at a pH value that approaches the is for all practical purposes independent of pH? Â&#x2021; Why can many phosphonates' performance in the cooling ÂżQDO SKRVSKRQLF DFLG S.D YDOXH Â´ *ULIÂżWKV

water pH range be modeled without incorporating inhibitor )LJXUHV DQG SURÂżOH WKH SURWRQDWLRQ VWDWH IUDFWLRQ IRU WKH phosphonates HEDP, ATMP (amino tris(methylene phosphonic) speciation or pH as a variable? acid), and HDTMPA versus pH. The red lines depict the active form. Robert J Ferguson French Creek Software, Inc. Valley Forge, PA 19481-0068

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7KH LPSDFW RI S+ DQG SURWRQDWLRQ VWDWH RQ WUHDWPHQW HIÂżFDF\ LV observed in many areas of water treatment. Chlorination provides an example with the protonated form of hypochlorous acid being observed to have much more biocidal activity than the dissociated alkaline hypochlorite form. Adsorption studies of inhibitors used as VTXHH]H WUHDWPHQWV LQ RLO ÂżHOG DSSOLFDWLRQV SURYLGH DQRWKHU H[DPSOH RI WKH HIÂżFDF\ RI GLVVRFLDWHG YHUVXV SURWRQDWHG LQKLELWRU IRUPV (Breen 1990). In some cases, such as bromination, the impact of GLVVRFLDWLRQ VWDWH RQ HIÂżFDF\ LV DUJXDEO\ QHJOLJLEOH Similar observations have been made concerning the impact of S+ DQG SURWRQDWLRQ VWDWH RQ HIÂżFDF\ LQ WKH FDVH RI VFDOH LQKLELWLRQ E\ SKRVSKRQDWHV DQG SRO\PHUV *ULIÂżWKV 5DPVH\ Tomson, 2002, Hunter, 1993). 6FDOH LQKLELWRUV GLVVRFLDWH OLNH RWKHU DFLGV DV LQ (TXDWLRQ (Eq. 1) H-Inhibitor <--> H+ + Inhibitor ZLWK D GLVVRFLDWLRQ FRQVWDQW WKDW PLJKW EH JHQHUDOL]HG DV (Eq. 2) Ka = {H+} {Inhibitor-}/{H-Inhibitor} DQG D S.D GHÂżQHG DV (Eq. 3) pKa = - log10(Ka) %\ GHÂżQLWLRQ S.a is the pH where 50% of the acid for a given dissociation step will be in the protonated form, and 50% in the dissociated form. Knowing the pKa IRU WKH ÂżQDO GLVVRFLDWLRQ VWHS 8

,W LV VLJQLÂżFDQW WR QRWH WKDW WKH ORZHU S.D RU WKH ÂżQDO GLVVRFLDWLRQ step for these phosphonates results in a high percentage of the inhibitor being in the active, dissociated state in the typical cooling water pH range. pH has a similar impact on polymer dosages for scale inhibition. 7KH ÂżUVW WLPH WKH DXWKRU HQFRXQWHUHG WKH QHHG WR FRUUHFW WKH GRVCTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

ages and models for speciation was in the development of a model for calcium phosphate scale inhibition by AA-AMPS (copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid). The data of minimum effective dosage versus saturation ratio and temperature was developed at three (3) distinct pH values in the cooling water range of 7.0 to 9.0 . 7KUHH GLVWLQFW VFDWWHU SORWV UHVXOWHG IURP WKH ÂżUVW PRGHO DWWHPSWHG a correlation of dosage as a function of driving force, induction time, and temperature (Eq. 4) Dosage = f(SR,time,temperature) Where Â&#x2021; SR is the ion association model saturation ratio for tricalcium phosphate; Â&#x2021; dosage is the active AA-AMPS concentration in the test solution; Â&#x2021; temperature is the absolute temperature; and Â&#x2021; time is the last time before failure. )LJXUH SURÂżOHV WKH GLVWULEXWLRQ RI VSHFLHV IRU WKH $$ $036 FRpolymer. The pKa IRU LWV ÂżQDO GLVVRFLDWLRQ VWHS LV DW D VLJQLÂżFDQWO\ higher pH than the comparable pKa V IRU WKH SKRVSKRQDWHV SURÂżOHG in Figures 1, 2, and 3. The red line indicates the high activity dissociated form. It can be seen that only a small percentage of the copolymer is in the active form (red line) in the typical cooling water pH range of 7 to 9, while a majority of the phosphonate concentration is in the active form for the same pH range. )LJXUH SURÂżOHV WKH SUHGLFWHG YHUVXV REVHUYHG YDOXHV IRU WKLV FRUUHODWLRQ ZLWK D ORZ FRHIÂżFLHQW RI GHÂżQLWLRQ 52) of 0.31 . Adding pH to the parameters modeled reduced the scatter plot to one zone, and increased the correlation to an R2 of 0.81, as depicted LQ )LJXUH S+ KDG D QHJDWLYH FRHIÂżFLHQW LQGLFDWLQJ WKDW GRVDJH when treated independently of saturation ratio, decreased with increasing pH (Ferguson, 1993). The pH factor in this case fol10

lowed the dissociation fraction and corrected for the speciation at the various pHs studied. 7KH ÂżQDO FRUUHODWLRQ FDOFXODWHG WKH VSHFLDWLRQ RI WKH LQKLELWRU DQG used the active concentration of the unprotonated form, rather than the total polymer dosage. Figure 7 depicts the correlation improvement when the dissociated inhibitor concentration is used for the model.

$33/,&$7,21 A knowledge of inhibitor speciation and activity versus pH is useIXO LQ VHOHFWLQJ DQG PDWFKLQJ LQKLELWRUV WR D VSHFLÂżF DSSOLFDWLRQ for developing performance test experimental design to develop LQKLELWRU SHUIRUPDQFH PRGHOV DJDLQVW VSHFLÂżF VFDOHV DQG IRU RStimizing dosages. (YDOXDWLQJ D WHUSRO\PHU ZLWK WKH DGGLWLRQ RI WKH ÂżQDO GLVVRFLDWLRQ constant resolved another polymer performance riddle. Laboratory data for the performance of a terpolymer seemed almost too good. CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

dosage calculated from a model is Dmin, and the alpha (fraction) for WKH ÂżQDO GLVVRFLDWLRQ VSHFLHV LV ÄŽ WKH XVH GRVDJH 'XVH ZRXOG EH (Eq. 5) Duse = Dmin ÄŽ For a optimized dosage Dmin of 1.0 mg/L and a dissociation fraction ÄŽ RI WKLV UHGXFHV WR (Eq. 6) Duse = 1.0 / 0.8 or 1.25 mg/L This method provides a simple, reasonably conservative, approach to correcting for active species versus total inhibitor concentration. It DVVXPHV WKDW WKH ÂżQDO GLVVRFLDWLRQ VSHFLHV LV WKH RQO\ DFWLYH PDWHULDO 'HYHORSLQJ 1HZ 0RGHOV ,GHDOO\ WKH H[SHULPHQWDO GHVLJQ IRU developing inhibitor models (Ferguson, 1992) would allow the UHVHDUFKHU WR FDOFXODWH WKH UHODWLYH HIÂżFDF\ RI HDFK LQKLELWRU IRUP LQ UHODWLRQ WR WKH ÂżQDO GLVVRFLDWHG IRUP $Q H[SHULPHQWDO GHVLJQ ZLWK a broad range of pH and saturation ratio would allow the researcher WR FDOFXODWH WKH UHODWLYH HIÂżFDF\ IRU HDFK VLJQLÂżFDQW VSHFLH IURP WKH LQKLELWRU GLVVRFLDWLRQ SURÂżOH 7KH SRO\PHU SHUIRUPHG DW DSSUR[LPDWHO\ D ÂżIWK WKH GRVDJH RI AA-AMPS copolymer under comparable conditions. Yet the model 2QFH WKH UHODWLYH HIÂżFDFLHV DUH FDOFXODWHG WKH GRVDJH PRGHO H[developed initially for the polymer using the relationship of equa- SDQGV WR WLRQ \LHOGHG U VTXDUHG FRUUHODWLRQ FRHIÂżFLHQW RI RQO\ ÂżJXUH (Eq. 7) Duse = Dmin ÄŽ1*eff1 ÄŽ2*eff2 ÂŤ ÄŽn *effn) $GGLQJ S+ DV D YDULDEOH LQFUHDVHG WKH FRUUHODWLRQ FRHIÂżFLHQW WR 7KLV HTXDWLRQ UHGXFHV WR HTXDWLRQ ZKHQ RQO\ WKH ÂżQDO GLVVRFLDWHG an acceptable value for experimental data. Using the dissociated IRUP LV VLJQLÂżFDQW inhibitor form in the model, as calculated from the terpolymer's pKa LQFUHDVHG WKH FRUUHODWLRQ FRHIÂżFLHQW WR ÂżJXUH 7KH 6800$5< performance increase might be attributed to the decrease in pKa S+ FDQ DIIHFW WKH HIÂżFDF\ RI VFDOH LQKLELWRUV 6RPH VSHFLHV RI LQhibitors are more active than others. The dissociated form, at the from 10.5 for the copolymer to 9.7 for the terpolymer. highest pH, tends to be the active specie. An understanding of the UHODWLYH HIÂżFDF\ RI LQKLELWRU VSHFLHV YHUVXV S+ FDQ JUHDWO\ LPSURYH models developed for calculating the minimum effective dosage, DQG IRU VHOHFWLQJ WKH RSWLPXP LQKLELWRU IRU D VSHFLÂżF DSSOLFDWLRQ

)857+(5 :25. /DERUDWRU\ VWXGLHV DUH SODQQHG WR GHYHORS GLVVRFLDWLRQ SURÂżOHV IRU commercial phosphonate and polymeric scale inhibitors, followed by inhibitor optimization studies over a broad pH range. The objective of the application research is to quantify the impact of pH on the HIÂżFDF\ RI FRPPHUFLDO LQKLELWRUV ZLWK LQLWLDO WHVWV VWXG\LQJ %D624, CaSO4, and CaCO3 inhibition. This paper provides background information and the rationale for the work.

REFERENCES

6HOHFWLQJ ,QKLELWRUV $ NQRZOHGJH RI GLVVRFLDWLRQ SURÂżOHV LV XVHIXO in selecting inhibitors for an application. For a low pH application, select an inhibitor with a low pKa, preferably below or within the pH range for the application. This assures that the maximum amount of inhibitor will be in the active form in the application pH range. 2SWLPL]LQJ 'RVDJHV 7RPVRQ HW DO 7RPVRQ UHFRPPHQG WKH use of a factor to correct dosage models for the active specie concentration expected. They incorporated the correction into models for minimum effective dosage. For example, if the minimum effective 12

1) Breen, P.J., Diel, B.N., and H.H. Downs, (1990), â&#x20AC;&#x153;Correlation of Scale Inhibitor Structure With Adsorption Thermodynamics and Performance in Inhibition of Barium 6XOIDWH LQ /RZ S+ (QYLURQPHQWV Â´ 6RFLHW\ RI 3HWUROHXP Engineers, Annual Technical Conference. 2) Ferguson, R.J., (1993), â&#x20AC;&#x153;Developing Scale Inhibitor DosDJH 0RGHOVÂ´ 1$&( (8523( 6DQGHIMRUG 1RUZD\ )HUJXVRQ 5 - Â´0LQHUDO 6FDOH 3UHGLFWLRQ DQG &RQWURO DW ([WUHPH 7'6Â´ ,QWHUQDWLRQDO :DWHU &RQIHUHQFH *ULIÂżWKV ' : 5REHUWV 6 ' DQG < 7 /LX Â´,QKLELWLRQ of Calcium Sulfate Dihydrate Crystal Growth by PhosSKRQLF $FLGV Âą ,QĂ&#x20AC;XHQFH RI ,QKLELWRU 6WUXFWXUH DQG 6ROXWLRQ S+ Â´ 6RFLHW\ RI 3HWUROHXP (QJLQHHUV ,QWHUQDWLRQDO Symposium on Oil Field and Geothermal Chemistry. 5) Hunter, M.A., (1993), Alkalinity and Phosphonate Studies for the Scale Prediction and Prevention, Rice University. 6) Ramsey, J.E., and L.M. Cenegy, (1985), â&#x20AC;&#x153;A Laboratory Evaluation of Barium Sulfate Scale Inhibitors at Low S+ IRU 8VH LQ &DUERQ 'LR[LGH (25 )ORRGV Â´ 6RFLHW\ RI Petroleum Engineers, Annual Technical Conference. 7) Tomson, M.B., Fu, G., Watson, M.A. and A.T. Kan, (2002), "Mechanisms of Mineral Scale Inhibition," Society of PeWUROHXP (QJLQHHUV 2LOÂżHOG 6FDOH 6\PSRVLXP $EHUGHHQ UK, 2002. CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

Understanding Vibration Switches David A. Corelli Imi Sensors Vibration Institute

Understanding Vibration Switches $EVWUDFW 7KH SDSHU SUHVHQWV WKH basics of both Mechanical and Electronic Vibration Switches, explains how they are designed, how they work, and show where they are effective and where they are not. It also discusses their frequency responses along with the major differences in the responses of mechanical and electronic switches. Finally, it shows how the various switches meet or do David A. Corelli not meet the new CTI Vibration Standard. A video is also included in the presentation that shows how the various vibration switches respond to unbalance using a long-stroke vibration shaker.

Figure 2: Traditional Mechanical Vibration Switch

Why Vibration Switches - Vibration switches are simple devices used to protect rotating machinery against catastrophic failure, particularly large fans as found on cooling towers. They continuously monitor vibration on a machine and provide an alert and/or shutdown of the machine when vibration levels become too high. Figure 1 shows a large fan that failed catastrophically due to high vibration.

Figure 3: Traditional Electronic Vibration Switch

Figure 1: Catastrophic failure of a large fan due to high vibration

Types of Vibration Switches - There are two basic types of vibration switches mechanical and electronic, however; with todayâ&#x20AC;&#x2122;s microprocessor technology, electronic vibration switches can be further subdivided into two types, traditional electronic and programmable electronic vibration switches.

Figure 4: USB programmable electronic vibration switch mounted on a motor

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Mechanical Vibration Switches - A mechanical vibration switch is a fairly simple device consisting of a magnet mounted on a spring loaded arm, which in turn is attached to a mechanically activated electrical switch, Figures 5 and 6. The switch is held in an armed position when the position of a magnetic plate is adjusted so it is close enough to the magnet to overcome the force in the spring loaded arm.

PDVV ZDV PRYHG IRU WKLV SKRWR WR VKRZ IXQFWLRQDOLW\ 1RWH WKH sprung mass does not move in the negative X direction, thus there is a large difference in the shock required to trip the switch in the plus and minus X directions.

Figure 7: The sprung mass is sensitive to motion in three axes.

)LJXUH $UPHG PHFKDQLFDO VZLWFK PHFKDQLVP ZLWK ODEHOOHG SDUWV

The above discussion highlights a key problem with of mechanical vibration switches. At low operating speeds, as seen for example in large cooling towers, the acceleration is so low that the inertial forces never get high enough to trip the switch in a pure unbalance condition, but, they do trip, so whatâ&#x20AC;&#x2122;s happening. If the unbalance gets high enough, there are secondary effects, typically impacting, that generate enough acceleration to cause the switch to trip. Advantages and Disadvantages â&#x20AC;&#x201C; The advantages of mechanical vibration switches are cost, simplicity, and two-wire operation unless a remote reset is required. It is also sensitive to vibration in all three planes of motion, although not equally as is often believed by users. The following test, Figure 8, was set up to determine the difference in sensitivity in the X, Y, and Z directions.

Figure 8: Impact test for mechanical vibration switches Figure 6: Tripped mechanical switch mechanism with labelled parts

The switch was set to a somewhat arbitrary trip level but fairly low. The switch was armed and then impacted using a calibrated impact KDPPHU LQ IRXU GLUHFWLRQV SOXV ; PLQXV ; < DQG = 7KH IRUFH levels required to trip the switch were recorded for each direction. This was done for both the traditional mechanical vibration switch and the new linear adjust mechanical vibration switch. The results are shown in Table 1. It is clear that in the X direction, it takes about half the shock or impact to trip the switch depending on the direction. Also, it takes about 3 times the shock or vibration to trip the traditional switch in the Y or Z axes. The directionality of the linear adjust switch seems to be much better.

The gap between the magnet and magnetic plate can be adjusted by an external screw adjustment to increase or decrease the magnetic force holding the spring loaded arm in an armed position. Unfortunately, not all mechanical switches have the same maximum gap or force adjustment per turn. Some switches have a maximum gap of 0.017 to 0.020 inches (4.3 to 5.1 mm) beyond which the magnetic force is not strong enough to overcome the spring force. Some mechanical switches can have gaps as high as 0.080 inches (2 mm). The sensitivity adjustment is also a function of the thread on the DGMXVWLQJ VFUHZ VRPH KDYH ÂżQH DQG VRPH KDYH FRXUVH WKUHDGV 7KXV the typical procedure for setting a mechanical screw, about Âź turn from the point where the switch trips on startup can very widely. When motion occurs, the magnet on the spring loaded arm and the sprung mass generate inertial forces that to oppose the magnetic force as governed by Newtonâ&#x20AC;&#x2122;s Second Law of Motion . When the acceleration level is high enough to generate an inertial force that is Table 1: Force required to trip the switches in three axes greater than the magnetic force, the switch trips. The spring loaded arm rests against a sprung mass that can move in three directions The sensitivity in the axis perpendicular to the surface of the magnet as shown in Figure 7 and thus mechanical switches are sensitive and plate, X direction, is much more sensitive than the other two in all three axes, albeit not equally as will be shown. The sprung axes, particularly in the case of the traditional mechanical vibra16

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tion switch because the inertial force due to shock and vibration is acting on both the inertial mass and the magnet in that direction. Since the inertia of the magnet from a shock in the -X direction KHOSV WR ÂłRSHQÂ´ WKH VZLWFK DQG RQH LQ WKH ; GLUHFWLRQ WR FORVH LW the vibration required to trip the switch is less in the -X than in the +X direction. The major disadvantages to a mechanical vibration switch are there is no accuracy in setting a trip level, it has different sensitivities in the various directions, it is not very repeatable, it will not trip due to a pure unbalance condition without secondary effects, and environmental sealing can be an issue due to the mechanical adjustment screw. Poor or no sealing compounds the problem due to moisture ingress causing corrosion and a change in switch sensitivity, often making it less sensitive to shock and vibration. CTI Standard - Section 4.2 of the proposed CTI Standard for Vibration Limits in Water Cooling Towers states the primary Fan Rotational Speed for cooling towers is 70 to 400 RPM (1.2 to 6.7 +] 7KH Âł&Â´ =RQH &ODVVLÂżFDWLRQ XQDFFHSWDEOH EDODQFH OLPLWV in the Fan Speed Displacement Tables run from about 11.5 mils on slower speed, 70 RPM, concrete cooling towers with pedestal PRXQWLQJ WR DERXW PLOV RQ ZRRG DQG ÂżEHUJODVV WRZHUV 2Q KLJKHU speed units, 400 RPM, it runs from about 4.1 mils on the concrete WRZHUV WR DERXW PLOV RQ WKH ZRRG DQG ÂżEHUJODVV XQLWV :KHQ those displacement limits are used and the associated accelerations computed, they are found to be incredibly small as shown in Table 2 below that use the worst case displacements at each speed.

Figure 9: Traditional electronic vibration switch with potentiometer and DIP switch adjustments

CTI Vibration Standard â&#x20AC;&#x201C; The table below is taken from the proposed CTI Standard for Vibration Limits in Water Cooling Towers DQG VKRZV WKH Âł%URDGEDQG 9LEUDWLRQ /LPLWVÂ´ RYHUDOO YLEUDWLRQ DPSOLWXGHV IRU ÂżHOG HUHFWHG ZRRG ÂżEHUJODVV IUDPHG IDFWRU\ DVVHPEOHG VWHHO DQG ÂżEHUJODVV FRROLQJ WRZHUV 7KH VKXWGRZQ OLPLW IRU WKHVH W\SHV RI WRZHUV LV VSHFLÂżHG DW LSV PP V SHDN YHORFLW\ 7KLV is the vibration shutdown level that the electronic vibration switch VKRXOG EH VHW WR ,W VKRXOG DOVR EH QRWHG WKDW WKLV VSHFLÂżFDWLRQ FDQQRW be met with a mechanical vibration switch. That is not to say that a machine or cooling tower cannot be protected with a mechanical switch, it just implies that greater accuracy can be achieved with an electronic switch and the Standard can be met. A word of caution, be sure to look at the frequency response of the electronic switch, most are accurate down to 2 to 3 Hz (120 to 180 RPM). Below those frequencies, the sensitivity of the switch drops off. Many electronic vibration switches have some or all of the following options available making them more versatile, effective, and providing better protection than mechanical vibration switches. Â&#x2021; Warning and critical (shutdown) alarms Â&#x2021; Time delays Â&#x2021; Latching and non-latching switch operation Â&#x2021; Raw vibration output Â&#x2021; 4-20 mA output

7DEOH $FFHOHUDWLRQ DQG YHORFLW\ OHYHOV FRUUHVSRQGLQJ to unacceptable balance conditions in the CTI Standard on cooling towers

Using the highest displacement, unbalance for each fan speed, it is clearly seen that the acceleration levels are too low to cause enough inertial force on the mechanical switch lever or inertial mass mechanisms to trip the switch. Thus, in a pure unbalance condition, a mechanical switch cannot trip the tower. The velocity levels, however, are measureable with modern piezoelectric accelerometers (PE) and thus an electronic switch that uses a PE accelerometer will catch a balance condition in most cases.

Electronic Vibration Switches Electronic vibration switches, Figure 9, are much more accurate and repeatable than mechanical vibration switches. They utilize a calibrated piezoelectric accelerometer, typically embedded in the switch housing, for sensing vibration and can integrate the signal to get velocity and in some cases displacement. As shown in the Table 2 above, unlike the mechanical switch, the electronic switch can, in most cases, accurately measure the balance condition of the fan and respond based on its amplitude. 18

Table 3: Broadband vibration limits for cooling towers from Table 1 of the proposed CTI Vibration Standard

Dual Alarms - When a vibration switch shuts down a machine, it will more than likely come at an inopportune time. By having two alarm levels and associated relays, a warning level can be speciÂżHG WKDW ZLOO WULS D UHO\ DQG SURYLGH DQ LQGLFDWLRQ LQ WKH IRUP RI D light, audible sound, or annunciator that will warn the user that the machine is getting close to a shutdown level allowing them time to react prior to an unexpected shutdown. Time Delays - Time delays are a big advantage of electronic vibration switches. There can be one or more delay types in electronic vibration switches with the most common being start up and alarm GHOD\V 7KH VWDUWXS GHOD\ DOORZV D Âż[HG RU SURJUDPPDEOH GHSHQGLQJ CTI Journal, Vol. 35, No. 2

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on the switch) amount of time where the vibration level is ignored to allow the machine to startup where it may have higher vibration prior to steady state operation. The alarm delay will require that the vibration level be above the alarm level for a certain amount of time prior to tripping. This would avoid a shut down for some random transient event like bumping into the machine. Additionally, some electronic vibration switches allow a maximum vibration level to be set during the startup delay, higher than the normal running level, but still protecting the unit should the levels get excessively high. Latching and Non-latching – Mechanical vibration switches, by default, are latching, meaning once they trip they stay tripped until reset by someone. An electronic vibration switch can operate this way as well but can also be set to non-latching. This means that after a relay is tripped, it will automatically reset itself when the vibration level drops below the alarm level. Raw Vibration Output – This provides the broadband analog time waveform directly from the embedded piezoelectric accelerometer for diagnostic purposes. A vibration data collector or other analysis device can be connected to the output for analysis. 4-20 mA Output – While the switch is providing protection, a 4-20 mA signal proportional to the overall vibration level can be sent to a PLC or other plant monitoring device in a control room for vibration monitoring purposes. Accuracy – As can be seen in Figure 9, alarm levels and time delays in traditional electronic vibration switches are often set using potentiometers and thus have some degree of uncertainty, $V ZLOO EH VKRZQ ZLWK WKH QHZHU SURJUDPPDEOH HOHFWURQLF vibration switches, setting are done via USB programming and are quite accurate.

Programmable Electronic Vibration Switches Programmable electronic vibration switches generally have a little better accuracy and provide better control over trip levels and delays than traditional electronic vibration switches allowing the user to tailor the response as desired. However, they may not have all of the

other features of traditional switches. Figure 4 shows a hermetically sealed USB programmable electronic vibration switch mounted on a motor. Figure 10 shows the programming screen and the large number of options there are for tailoring the alarm levels and delays.

Figure 10: Programming screen for USB programmable electronic vibration switch

Conclusion Any vibration switch offers protection against damaging vibrations if set and used properly. Electronic vibration switches are more accurate, can directly protect against a pure unbalance condition, and many can meet the newly proposed CTI Standard for Vibration Limits in Water Cooling Towers. Traditional electronic vibration switches currently have more options than programmable units but also cost more. It is up to the user to determine what vibration switch is best for their application.

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6WUXFWXUDO 0RGLÂżFDWLRQ 2I $ 3RZHU 3ODQWÂśV 5LYHU :DWHU ,QWDNH 7R 0LQLPL]H ,FH %ORFNDJH Frank Michell American Electric Power Marcela Politano, Yushi Wang Iihr- Hydroscience & Engineering, University Of Iowa Jeff Stallings Electric Power Research Institute

cooling to condense the steam. In the 1970s three DGGLWLRQDO WDQJHQWLDOO\ ÂżUHG ERLOHUV ZHUH DGGHG (Unit 4 â&#x20AC;&#x201C; 780 MW and Units 5 & 6 â&#x20AC;&#x201C; 375 MW/ea), all using cooling towers.

Figure 1 shows the water intake in the AEP Conesville Power Plant. Historically, the plant routed a portion of warm water from the once-through cooling system to the intake area during winter months to control ice accumulation in the river intake. Unit $EVWUDFW 3, the last unit operating with this once-through Ice blockage of a power plant's water intake is cooling system, was retired at the end of 2012. The of paramount importance since it can lead to an remaining units only require cooling tower makeup unplanned shutdown of the intake compromising water. As a result, the amount of water needed for water supply and plant operation. American Electric cooling was drastically reduced to one third of past Power's (AEP) Conesville Power Plant historically )UDQN 0LFKHOO amounts. However, with the retirement of unit 3, the controlled ice accumulation at the river intake by plant lost the ability to control ice buildup in the intake. routing to the intake a portion of the warm water return from the condenser on the only operating "once-through" unit's circulating water system. The unit operating with this once-through cooling system was retired at the end of 2012; thus, the plant lost the use of the FRQGHQVHU RXWOHW ZDUP ZDWHU UHWXUQ GHLFLQJ Ă&#x20AC;RZ DW WKH ULYHU LQWDNH A numerical study was conducted to evaluate design alternatives to alleviate ice accumulation at the river intake. A numerical model to predict the ice transport and accumulation at the river intake was developed. The model was then used to understand the main phenomenon leading to ice transport to the intake and potential blockage. The effectiveness of several mitigation measures was evaluated with the model. Based on model results, a mitigation plan consisting of LQWDNH PRGLÂżFDWLRQV WR EH LPSOHPHQWHG GXULQJ VHYHUDO SKDVHV ZDV GHYHORSHG ,Q WKH ÂżUVW SKDVH ODUJH SLSH RSHQLQJV DUH FXW LQ WKH walls separating intake pump wells of previously retired units at the facility. In the second phase, a number of control vanes previously placed in front of the intake to control sediments are removed to facilitate downstream ice transport. A third phase, if needed to be implemented, involves removing additional sediment control vanes and cutting holes in the pump wells on the operating units. The paper describes the model, discusses numerical results and SUHVHQWV WKH ÂżHOG H[SHULHQFH DIWHU LPSOHPHQWDWLRQ RI SKDVH RQH

Introduction Ice accumulation on an intake trash rack can be abrupt, leading in extreme cases to a complete blockage of the trash rack and an unplanned shutdown of the intake facility. The complete blockage of water supply will severely impact the plant operation and power generation. 7KH $(3 &RQHVYLOOH FRDO ÂżUHG SRZHU SODQW ORFDWHG RQ WKH 0XVNLQJum River in Ohio, initially operated with three small boilers (Units 1 & 2 â&#x20AC;&#x201C; 125 MW/ea and Unit 3 â&#x20AC;&#x201C; 165 MW) using once-through

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$FFRUGLQJ WR ÂżHOG REVHUYDWLRQV LQ WKH 0XVNLQJXP 5LYHU QHDU WKH water intake, transport of ice from the river upstream is the primary cause of ice accumulation at the intake. Ice transported by surface water to the intake structure adheres to and accumulates in the trash racks when sustained ambient temperature is below freezing. Figure 2 shows the Conesville Plant water intake partially blocked with ice GXULQJ D W\SLFDO ZLQWHU GD\ ,FH DFFXPXODWHV ÂżUVW RQ WKH XSVWUHDP end of the intake and then gradually spreads to the downstream VHFWLRQV LI HQRXJK LFH LV WUDQVSRUWHG WR WKH LQWDNH $ VLJQLÂżFDQW LFH cover is formed upstream of the intake. Note that the ice cover is not attached to the shore or on the bank, which suggest that it is originally created from the ice accumulated in the intake. The river hydraulics near the Conesville Plant water intake is VWURQJO\ LQĂ&#x20AC;XHQFHG E\ VHGLPHQW FRQWURO VWUXFWXUHV 6&6 EXLOW LQ 2000 to control riverbed sediment ingestion at the intake [1]. The structures comprise a guide wall upstream of the intake, thirteen submerged vanes arranged in two rows, and a skimming wall [2]. These structures had been very effective in maintaining a protective barrier DJDLQVW VHGLPHQWV GXULQJ WKH ÂżUVW VL[ \HDUV RI RSHUDWLRQ +RZHYHU CTI Journal, Vol. 35, No. 2

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in 2006 sedimentation started to build up around the downstream Figure 3. Study area and bathymetry. vanes, and in 2009 a complete dredging of the area was necessary. ,W LV EHOLHYHG WKDW H[WUHPH Ă&#x20AC;RRGLQJ ULYHU FRQGLWLRQV DQG UHGXFWLRQ The river hydrodynamics is solved with the RANS equations for RI WKH SODQWÂśV LQWDNH Ă&#x20AC;RZ GXH WR UHWLUHPHQW RI ÂłRQFH WKURXJKÂ´ 8QLWV LQFRPSUHVVLEOH Ă&#x20AC;RZV > @ 1& 2 at Conesville Plant have contributed to the sediment build-up. Little is known about the effect of the sediment structures on the Ă&#x20AC;RZ SDWWHUQ DQG LFH WUDQVSRUW WR WKH LQWDNHV $ EHWWHU XQGHUVWDQGLQJ of reasons that reduced the effectiveness of the SCS is also needed. A model capable of predicting the hydrodynamics and ice transport in the river is important to better comprehend the physical process the momentum source represents the pressure change due to ice leading to intake blockage or sediment accumulation. accumulation in the trash racks. The turbulence is modeled with a Mathematical models have been developed in the last several de- VWDQGDUG PRGHO ZLWK ZDOO IXQFWLRQV cades to describe river ice processes [3]. Current computer resources have made possible the use of Computational Fluid Dynamics (CFD) tools for modeling ice transport and accumulation in intakes. In this study, a three-dimensional (3D) numerical model based on the incompressible Reynolds Average Navier Stokes (RANS) equations together with a k-epsilon model for turbulence closure are used. The RANS equations are appropriate to obtain time-averaged VROXWLRQV WR WKH 1DYLHU 6WRNHV HTXDWLRQV IRU WXUEXOHQW Ă&#x20AC;RZV > @ An energy equation is used to predict temperature distribution. A particle tracking technique is incorporated in the model to obtain ice trajectories. Buoyancy, drag, and turbulent dispersion forces are included. The pressure drop due to accumulation of ice in the The temperature is calculated from the energy conservation equation trash racks is modeled, including a porous media with a porosity IRU LQFRPSUHVVLEOH Ă&#x20AC;RZV QHJOHFWLQJ SUHVVXUH ZRUN HQHUJ\ VRXUFH IXQFWLRQ RI DFFXPXODWHG LFH 7KH PRGHO ZDV XVHG WR HYDOXDWH GXH WR YLVFRXV GLVVLSDWLRQ DQG NLQHWLF HQHUJ\ possible ice accumulation with present operations, (2) assess the effect of the SCS on the hydrodynamics and transport of ice to the intake region, and (3) analyze some possible mitigation measures. A Lagrangian approach, which uses Newtonâ&#x20AC;&#x2122;s Second Law, is used 6WXG\ $UHD WR FRPSXWH LFH WUDMHFWRULHV The modeled domain extended approximately 1,000 ft upstream of the intake (Figure 3). Bathymetric NAVD88 data collected in 2009 and 2010 were used in the model. the subscript stands for ice particle. The last term on the right-hand VLGH UHSUHVHQWV EXR\DQF\ 7KH GUDJ IRUFH LV REWDLQHG IURP

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7KH GUDJ FRHIÂżFLHQW GHSHQGV RQ WKH Ă&#x20AC;RZ UHJLPH DQG SDUWLFOH VKDSH Before any ice accumulation the porosity is one, and when a comIn this study, ice particles with diameter smaller than 10 mm are plete blockage occurs, â&#x20AC;Ť = ×&#x2039;â&#x20AC;Ź0 . i FRQVLGHUHG VSKHULFDO ZLWK D GUDJ FRHIÂżFLHQW JLYHQ E\

Numerical Model

where the particle Reynolds number is Bigger particles are approximated by perfect discs with constant thickness. The diameter-to-thickness ratio of ice crystal discs is asVXPHG WR EH > @ DQG WKH GUDJ FRHIÂżFLHQW LV PRGHOHG DV

0RGHO *ULGV The commercial grid generator Gridgen, was used to create the numerical grids. The river and water intake areas, with and without the SCS, were meshed with multi-block grids containing only hexahedral elements. Gridgen allows grid quality control near structures, river bed and free surface by projection in databases and selection RI QRGH GLVWULEXWLRQ :DWHU VXUIDFH HOHYDWLRQ ZDV FRQVLGHUHG Ă&#x20AC;DW Grid points were clustered, and nodes were highly concentrated QHDU WKH IUHH VXUIDFH DQG LQWDNH VWUXFWXUH WR UHVROYH Ă&#x20AC;RZ ÂżHOGV QHDU the interest area. Figure 4 shows a general view of the entire grid with boundary conditions. Details (a) and (b) show the grid near the intake at the water surface elevation and river bed, respectively. Two grids, with and without the SCS, were created. The same grid WRSRORJ\ ZDV XVHG IRU ERWK FRQÂżJXUDWLRQV WR DYRLG DQ\ HIIHFW RI the grid on the results.

ZKHUH FRHIÂżFLHQWV b1, b2, b3 and b4 are functions of the shape factor,

, with a as the surface area of a sphere having the

same volume as the particle, and A as the actual surface area of the particle. A Random Walk Model (RWM) is used to account for the dispersion of particles due to turbulence. Turbulent dispersion is WDNHQ LQWR DFFRXQW XVLQJ WKH LQVWDQWDQHRXV Ă&#x20AC;XLG YHORFLW\ instead of the mean velocity , being the fluctuating velocity. The RWM assumes that u'i (t) conforms to a Gaussian SUREDELOLW\ GLVWULEXWLRQ > @

where Č&#x; is a Gaussian distributed random number having zero mean and unity variance. The pressure drop through the trash racks without ice is modeled as a one-dimensional (1D) porous media. The pressure change across WKH WUDVK UDFNV FDQ EH PRGHOHG FRQVLGHULQJ DQ LQHUWLDO ORVV WHUP

A 3D porous media in the trash racks is included in the model to account for the pressure drop due to accumulated ice in the intake. The model assumes that all ice particles in contact with the screen will adhere to the rack, neglecting growth/decay of crystals due to heat transfer. The momentum sink in Eq. (2) due to ice accumulaWLRQ FDQ EH PRGHOHG DV

)LJXUH 0XVNLQJXP 5LYHU JULG *ULG GHWDLOV DW WKH IUHH VXUIDFH (a) and at the river bed (b).

Boundary Conditions )UHH 6XUIDFH WKH ZDWHU VXUIDFH LV PRGHOHG XVLQJ D ULJLG OLG DSSURDFK LPSRVLQJ ]HUR VKHDU VWUHVV 7KH KHDW Ă&#x20AC;X[ DW WKH IUHH VXUIDFH LV FDOFXODWHG IURP

ZKHUH K LV WKH KHDW WUDQVIHU FRHIÂżFLHQW ,Q WKLV VWXG\ K %78 ft2/h/oF [7]. :DOOV DQG 5LYHU %HG QRQ VOLS FRQGLWLRQ DQG ]HUR KHDW Ă&#x20AC;X[ DUH XVHG for the river banks and bed. 2XWĂ&#x20AC;RZV ]HUR JUDGLHQWV IRU DOO YDULDEOHV ZLWK WKH H[FHSWLRQ RI pressure are imposed at the downstream end of the river and at the LQWDNH XQLWV 3UHVVXUH LV DGMXVWHG WR VDWLVI\ WKH VSHFLÂżF GLVFKDUJH ,QĂ&#x20AC;RZ WKH WRWDO ULYHU Ă&#x20AC;RZUDWH DQG PHDVXUHG WHPSHUDWXUH DUH VSHFLÂżHG DW WKH XSVWUHDP VHFWLRQ 7XUEXOHQW YDULDEOHV DUH DVVXPHG WR EH zero.

The porosity of the trash rack considering the accumulated ice can be calculated considering the ratio between the volume available IRU Ă&#x20AC;RZ RI ZDWHU DQG WKH WRWDO SRURXV PHGLD YROXPH

Numerical Method The commercial code Fluent 12.1 was used in this study. User 'HÂżQHG )XQFWLRQV ZHUH SURJUDPPHG WR LQFOXGH WKH SUHVVXUH GURS due to ice accumulation in the intakes (Eq. 12). CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

the Niagara and St. Claire Rivers are in comparable climates to the Muskingum River. Note that the scaling performed in this study is not valid to accurately calculate the amount of ice in the Muskingum River. Rather it provides a model input to evaluate different 8QVWHDG\ VROXWLRQV ZHUH REWDLQHG XVLQJ D Âż[HG WLPH VWHS RI V structural alternatives related to ice transport and accumulation in Unsteady ice trajectories were computed integrating Eq. (7) with the intake area. D Âż[HG WLPH VWHS RI V ,PSOLFLW DQG WUDSH]RLGDO VFKHPHV ZHUH (IIHFW 2I 2SHUDWLRQDO &RQGLWLRQV $QG chosen as low- and high-order schemes for the discrete phase model Sediment Control Structures based on Fluent accuracy requirements and stability range for each Four simulations were performed to investigate the effect of the scheme. LQWDNH RSHUDWLRQ DQG 6&6 RQ WKH Ă&#x20AC;RZ SDWWHUQ DQG LFH WUDQVSRUW WR the intake facility. Table 1 describes intake operation conditions. Simulation Conditions 7KH ULYHU Ă&#x20AC;RZ ZDV GHWHUPLQHG EDVHG RQ KLVWRULF DQDO\VLV RI ZDWHU Simulations S1 and S2 represent past operations, and S3 and S4 GLVFKDUJHV GXULQJ ZLQWHU DYDLODEOH RQ KWWS ZDWHUGDWD XVJV JRY XVD current operations after the last unit operating with the once-through nwis/sw at Coshocton Station, Station No. 03140500. Average and cooling system was decommissioned. Note that there are eight PRVW IUHTXHQW Ă&#x20AC;RZV ZHUH DQDO\]HG WR VHOHFW D UHSUHVHQWDWLYH Ă&#x20AC;RZ intake wells, with 1A and 1B for unit 1, 2A and 2B for unit 2, 3A IRU WKH VLPXODWLRQV 7KH DYHUDJH Ă&#x20AC;RZ UDWH IRU WKH SDVW VHYHQ \HDUV and 3B for unit 3, and 4A and 4B for units 4-6, which only need during winter was approximately 9,900 cfs. Figure 5 is a frequency makeup water for cooling towers. SORW VXPPDUL]LQJ GLVWULEXWLRQDO LQIRUPDWLRQ RI WKH ULYHU Ă&#x20AC;RZ UDWH 0RVW RI WKH \HDU ULYHU Ă&#x20AC;RZV DUH LQ WKH ORZHU Ă&#x20AC;RZ UDQJH EHWZHHQ 1,000 and 8,000 cfs. Since ice accumulation is more critical durLQJ ORZ Ă&#x20AC;RZ HYHQWV LQ WKH ZLQWHU VLPXODWLRQV ZHUH UXQ DW D ULYHU Ă&#x20AC;RZ RI FIV )RU WKLV Ă&#x20AC;RZUDWH WKH ZDWHU VXUIDFH HOHYDWLRQ calculated using USGS gauge readings at the Muskingum River Coshocton Station was 721.6 ft. For this condition, the top of sediment vanes are located 9.6 ft beneath the free surface. Based on air and water temperatures measured during the winter of 2010, a low DLU WHPSHUDWXUH RI R) ZDV XVHG WR FRPSXWH WKH KHDW Ă&#x20AC;X[ DW WKH Table 1. Operating conditions for simulations S1 to S4 free surface (Eq. 13). An average river water temperature of 34.4oF Figures 6(a) and 6(b) respectively show 3D streamlines colored by was used at the model inlet. velocity magnitude without and with the SCS for the past operation. The length of the dashes in the streamlines is proportional to the YHORFLW\ PDJQLWXGH $V REVHUYHG LQ WKH ÂżHOG WKH PRGHO SUHGLFWV D big eddy with low velocity at the shallow region in front of the inWDNHV QHDU WKH ZHVW RSSRVLWH VKRUH 9DQHV FUHDWH Ă&#x20AC;RZ UHVLVWDQFH WKDW decrease streamwise velocities, inducing a small counterclockwise eddy upstream of the intake entrance. The SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm was used to couple pressure and velocity. The stanGDUG GLVFUHWL]DWLRQ PHWKRG ZDV DSSOLHG WR SUHVVXUH DQG ÂżUVW RUGHU upwind schemes were used for momentum and turbulent variables.

)LJXUH 0XVNLQJXP 5LYHU Ă&#x20AC;RZ IUHTXHQF\ SORW

The amount and size of ice in the model inlet are needed as boundary FRQGLWLRQV 7KHVH YDULDEOHV GHSHQG RQ WKH VLWH DQG WLPH ,GHDOO\ ÂżHOG data collected during several years would be used to determine the PHDQ YDULDEOHV UHTXLUHG DV LQSXWV WR WKH PRGHO 6LQFH D ÂżHOG VWXG\ WR determine ice characteristics was not carried out in the Muskingum River, ice concentration at the upper Niagara River was scaled and used in the simulations [8]. Ice size distribution was assumed to be the same as that measured in the St. Claire River [9, 10]. Both

Figure 6. Streamlines for S1 (a) and S2 (b)

CTI Journal, Vol. 35, No. 2

Figure 7 is a top view with streamlines colored by elevation, showing vortices at the trailing edge of the vanes. Vanes create a secondDU\ FLUFXODWLRQ LQ WKH Ă&#x20AC;RZ LQGXFLQJ KHOLFRLGDO YRUWLFHV WKDW LQGXFH scouring and control bed elevation [11]. If the intake is not operating, vane-induced vortices are not created and sediment accumulation is not prevented. This is consistent with the recent bathymetric data. When units 1 and 2 were shut down and intakes 1 and 2 stopped operating, sediment deposition started to occur, and the bed rose to such a level that some vanes were covered. Note that, in this case, the vanes are no longer functional. Figure 8 shows velocity vectors near the intake at 0.1 ft beneath the free surface, with and without the sediment control structures. For all the simulated operations, the sediment control structures increase the transverse velocity near the free surface (velocity in the intake direction), which facilitates the transport of ice to the intake entrance.

)LJXUH 6WUHDPOLQHV QHDU WKH LQWDNH IRU 6

near the intakes. The reduction of streamwise velocity decreases the downstream ice transport with potential to draw more surface frazil and pulverized ice into the intake. This condition is more FULWLFDO IRU SDVW RSHUDWLRQ ZKHUH ZDWHU LV Ă&#x20AC;RZLQJ WR WKH FHQWUDO region of the intake. Without the SCS, ice moves downstream near the intake region, and small particles turn back to the intake entrance. Medium and large VL]H SDUWLFOHV PRYH GRZQVWUHDP ZLWK WKH ULYHU Ă&#x20AC;RZ Without the vanes, warmer water from lower elevations is drawn to the intakes. The upstream eddy is located deeper and extends further downstream into the intake region than that predicted with the vanes in place. Larger transverse velocities with the SCS favor the transport of bigger ice particles to the intake entrances. The accumulation of ice starts near the free surface, where most of the ice particles are IRXQG ,FH DFFXPXODWLRQ RFFXUV ÂżUVW DW WKH XSVWUHDP HQG RI WKH intake structure and then extends toward the downstream side. The upstream eddy traps ice particles, facilitating their accumulation and the creation of a stationary ice cover upstream of the intakes. The ice cover grows in size due to further accumulation of ice particles. The rate of intake blockage is measured with the porosity of the porous media used to model ice accumulation in the intake. A value of one indicates an intake without any ice. It is assumed that when the porosity is 0.1, a complete blockage occurs and the intake is no longer functional. For comparison purposes, the porosity of the intake is plotted against non-dimensional time t*, which is the time divided by the time at which total blockage occurs. Figure 9 shows the evolution of porosity with and without the SCS for past and current operations. With past operation (simulations S1 and S2), more water is drawn into the intakes. Without the SCS, ice can turn back more easily after the recirculation. These ice particles are then transported to the intake area. According to the model, intakes 3A and 3B are blocked when t*~ 0.1. However, the intake 4A is not blocked during the simulated time. For present operation without the

Figure 8. Velocity vectors for (a) S1, (b) S2, (c) S3, and (d) S4

Near the free surface, the eddy upstream of the intakes is stronger when vanes are in place. This eddy decreases the streamwise velocLW\ XSVWUHDP RI WKH LQWDNH HQWUDQFH ZLWK SRWHQWLDO RI UHYHUVH Ă&#x20AC;RZ

Figure 9. Porosity for (a) S1, (b) S2, (c) S3, and (d) S4

CTI Journal, Vol. 35, No. 2

SCS (simulation S3), only a small amount of small ice particles are transported to the intake entrance, and the intakes are not blocked. With the SCS (simulation S4), all intakes are blocked in a relatively short period of time due to the accumulation of ice particles. Contrary to what is predicted in the simulations without the vanes, the EORFNDJH RFFXUV ÂżUVW LQ WKH XSVWUHDP LQWDNHV FRQVLVWHQW ZLWK ÂżHOG observations. The most critical condition takes place under current operation, where water is drawn from the upstream intake. According to the model, at t*~ 0.05 the intake is completely blocked. For past operation, intakes 3A and 3B operate longer than intake 4A. However, they are also blocked in a relatively short time (t*~ 0.2).

7DEOH 2SHUDWLQJ FRQGLWLRQV IRU VLPXODWLRQV 6 WR 6

Evaluation Of Mitigation Measures

Figure 11 shows ice distribution predicted with the particle tracking technique near the intakes at a time corresponding with 50% of total blockage. Details (a), (b) and (c) show the results when all intakes are drawing water with four, eight and zero vanes removed, respectively. Detail (d) shows the particles when operating with pump 4A. Details (e) and (f) show the results obtained when connecting intakes 1 and 2 with four and zero vanes removed, respectively. No VLJQLÂżFDQW GLIIHUHQFH LV REVHUYHG LQ WKH SUHGLFWHG Ă&#x20AC;RZ SDWWHUQ ZLWK DOO YDQHV LQ SODFH RU UHPRYLQJ IRXU GRZQVWUHDP YDQHV 7KH Ă&#x20AC;RZ pattern upstream of the intake is mainly affected by upstream vanes, and therefore removal of downstream vanes only has a marginal effect on the upstream eddy and ice transport to the intake area. When water is drawn with only one pump, higher velocities are predicted near intake 4A. However, this phenomenon is extremely local and GRHV QRW DIIHFW WKH JHQHUDO Ă&#x20AC;RZ SDWWHUQ LQ WKH LQWDNH DUHD $FFRUGLQJ to the model, the ice particles accumulate farther downstream as Eight numerical simulations were performed to evaluate the ef- the number of vanes removed increases. Reducing the number of IHFWLYHQHVV RI WKH SURSRVHG LQWDNH PRGLÂżFDWLRQV DV GHVFULEHG LQ XSVWUHDP YDQHV UHVXOWV LQ OHVV Ă&#x20AC;RZ UHVLVWDQFH IDYRULQJ GRZQVWUHDP Table 2. The effects of removing four and eight downstream vanes ice accumulation. were studied. A pump capacity of 89.12 cfs was used. This is a conservative assumption, since normal system demand is about KDOI RI WKDW YDOXH 7KUHH RSHUDWLRQDO FRQGLWLRQV ZHUH HYDOXDWHG 1) pumps 4A and 4B operating at 44.56 cfs/each, 2) pump 4A at 89.12 cfs, and 3) pump 4A operating at 89.12 cfs until plugged, and then switching to pump 2B operating at 89.12 cfs. According to the model, the accumulation of ice particles with current operation is comparable with past operation, and therefore there is an important risk of intake blockage by ice. Structural PRGLÂżFDWLRQV LQ WKH LQWDNH ZHUH SURSRVHG WR UHGXFH WKH SRWHQWLDO RI EORFNDJH )LJXUH 7KH PRGLÂżFDWLRQV FRQVLVW RI WKLUW\ LQFK pipe openings in the existing walls that separate the pump wells. A knife gate shut off valve was installed to enable isolation of the 2B ,QWDNH 3XPS ZHOO IRU PDLQWHQDQFH 7ZR RSWLRQV ZHUH SURSRVHG connecting all intakes, and 2) connecting intakes of retired units 1 and 2. Since partially or totally covered sediment control vanes are not functional, the removal of the downstream vanes was recommended. The 2B Emergency Booster Pump which can supply make-up water to the plant when the normal make-up pumps, 4A & 4B, are not operable will be placed in service on a weekly basis to help prevent sedimentation and verify operability of the equipment.

)LJXUH 3URSRVHG LQWDNH PRGLÂżFDWLRQ )LJXUH ,FH ORFDWLRQ IRU D 6 E 6 F 6 (d) S8, (e) S9, and (f) S10

CTI Journal, Vol. 35, No. 2

The model cannot predict actual time to blockage, since the amount of ice upstream in the river is unknown. However, under the same river conditions, it can be used to compare different geometries or mitigation measures using the operation time of an intake. The RSHUDWLRQ WLPH RI DQ LQWDNH LV GHÂżQHG DV WKH WLPH EHIRUH EORFNage. The operation time for the projected operation with water being drawn from intake 4A and the current intake geometry is t*~ 0.025. Table 3 shows the dimensionless operation time with the proposed VWUXFWXUDO PRGLÂżFDWLRQV ,Q RUGHU WR HYDOXDWH WKH HIIHFWLYHQHVV RI D VWUXFWXUDO PRGLÂżFDWLRQ WKH UDWLR EHWZHHQ RSHUDWLRQ WLPHV XQGHU GLIIHUHQW FRQGLWLRQV FDQ EH FDOFXODWHG DV

ZKHUH LV WKH RSHUDWLRQ WLPH ZLWK WKH SURSRVHG PRGLÂżFDWLRQ DQG WKH time with the original intake. Table 3 summarizes operation time and for simulations S5 to S10. can be used to calculate the increment LQ RSHUDWLRQ WLPH GXH WR D SURSRVHG PRGLÂżFDWLRQ )RU H[DPSOH connecting all intakes and removing four vanes (simulation S5) results in operation 16 times longer (before 50% intake blockage) than the current system.

Figure 12. Openings in the pump pit walls

Numerical results indicate that connecting all intakes results in longer time before intake blockage. The difference in intake operaWLRQ WLPH ZKHQ UHPRYLQJ IRXU GRZQVWUHDP YDQHV LV QRW VLJQLÂżFDQW However, ice particles are less attracted to the intake region when upstream vanes, i.e., vanes in front of intake 3, are also removed. 7KH SURSRVHG PRGLÂżFDWLRQV KHOS WR DOOHYLDWH LFH DFFXPXODWLRQ LQ the intakes. However, ice transport to the intake entrance is not fully prevented.

)LJXUH .QLIH JDWH YDOYH LQVWDOODWLRQ LQ SURJUHVV

7KH PRGLÂżFDWLRQV WR FRQQHFW WKH SXPS SLWV ZHOOV IURP UHWLUHG XQLWV and 2 and the isolation knife gate valve installation were completed in December, 2012. 7DEOH 2SHUDWLRQ 7LPH DQG IRU VLPXODWLRQV 6 WR 6

)LHOG ([SHULHQFH $IWHU ,QWDNH 0RGLÂżFDWLRQV

Ambient and river temperatures experienced during winter months LQ DQG IROORZLQJ FRPSOHWLRQ RI WKH PRGLÂżFDWLRQV ZHUH Based on model results, a mitigation plan to be implemented in unseasonably mild. There were freezing conditions but they did not VHYHUDO SKDVHV ZDV SUHSDUHG ,Q WKH ÂżUVW SKDVH LQFK GLDPHWHU last long enough to result in ice accumulations forming in the river pipe openings are cut in the walls separating intake pump wells 1 in the vicinity of the Conesville Plant intake. and 2. Figure 12 shows the openings in the pump pit walls. An isolation valve is installed to enable dewatering the 2B intake pump pit Early in January, 2014, the polar vortex brought extreme cold (Figure 13). A pipe opening larger than simulated was constructed. weather to a large portion of the United States. On January 7, This pipe with 36 inch-diameter in lieu of 30 inch-diameter is temperatures abruptly decreased in the Conesville area. A drop of expected to result in longer intake operation time. In the second roughly 35 oF took temperatures to a low of -8 oF and a high on phase, sediment control vanes placed in front of non-operating intake January 8 of 9 oF. As shown in Figure 14, there were considerable units will be removed to facilitate downstream ice transport. A third DPRXQWV RI LFH Ă&#x20AC;RDWLQJ GRZQ WKH ULYHU ,FH SDWWHUQV FORVHO\ PDWFKHG phase involving removal of additional sedimentation control vanes WKH SUHGLFWLRQV IURP WKH QXPHULFDO DQDO\VLV ,FH DFFXPXODWHG ÂżUVW DW and cutting holes in all pump wells will be implemented if needed. the upstream end of the intake structure and then extended toward the downstream side. The traveling water screen on the 4B pump intake was overloaded due to ice weight load. The traveling water

,QWDNH 0RGLÂżFDWLRQV

CTI Journal, Vol. 35, No. 2

screens tripped and remained out of service to prevent additional ice accumulation by the sprays from the screen wash system. As planned, the emergency booster pump 2B was used for meeting SODQW LQWDNH Ă&#x20AC;RZ UHTXLUHPHQWV +DYLQJ WKH GRZQVWUHDP LQWDNHV interconnected ensured a reliable supply of water to the booster pump suction and for the plant needs.

sary, includes the removal of three additional vanes and connection of all intake units/pump pits. During the winter of 2014, temperature was well below freezing for an extended period of time and ice transported from the river upstream accumulated at the intake structure. Ice behavior and accumulations at the intake closely matched the predictions from the model. AEP will monitor the icing characteristics during following ZLQWHUV WR GHWHUPLQH LI DGGLWLRQDO L H VHFRQG SKDVH PRGLÂżFDWLRQV DUH QHFHVVDU\ ZDUUDQWHG 7KH :LQWHU ÂżHOG H[SHULHQFH VHHPV WR LQGLFDWH WKDW WKH LPSOHPHQWHG LQWDNH PRGLÂżFDWLRQV PD\ be enough to ensure continuous, reliable water supply to the plant during extreme cold weather.

Nomenclature a

surface area of a sphere having the same volume as the particle

surface area of the particle

VKDSH IDFWRU FRHIÂżFLHQW

GUDJ FRHIÂżFLHQW

VSHFLÂżF KHDW

C Ń&#x201C; = 1.44, C Ä° = 1.92, CČ? = 0.09 Č&#x203A; Ä° model constants )LJXUH ,FH LQ 0XVNLQJXP 5LYHU RQ -DQ

Conclusions

particle diameter

drag function

v g

gravitational acceleration

Ice transport and accumulation at the water intake in the AEP generation of turbulent kinetic energy Conesville power plant were analyzed with a numerical model. GČ&#x20AC; KHDW WUDQVIHU FRHIÂżFLHQW 1XPHULFDO VLPXODWLRQV ZHUH SHUIRUPHG IRU D W\SLFDO ULYHU Ă&#x20AC;RZ h during winter months. Çž roughness height 7KH PRGHO SUHGLFWHG YDQH LQGXFHG YRUWLFHV DQG WKH JHQHUDO Ă&#x20AC;RZ ČĄ pressure SDWWHUQ REVHUYHG LQ WKH ÂżHOG $FFRUGLQJ WR WKH PRGHO REVHUYHG KHDW Ă&#x20AC;X[ DW WKH IUHH VXUIDFH sediment deposition was caused by the shutdown of units 1 and 2. q second When these units stopped operating, secondary recirculations were s i not present and sediment was deposited. momentum source 7KH PRGHO SUHGLFWV WKDW LFH DFFXPXODWLRQ RFFXUV ÂżUVW LQ WKH XSVWUHDP S LQWDNH DQG WKHQ LQ WKH GRZQVWUHDP SDUW DV REVHUYHG LQ WKH ÂżHOG S modulus of the mean rate-of-strain tensor ij Sediment control structures create hydrodynamic conditions that t* dimensionless operation time facilitate ice transport to the intake and attract bigger ice particles. T temperature The intake blockage time for the past and current operations is air temperature comparable. According to the model, ice buildup in the trash racks Ta could result in complete blockage of the intake facility, compromis- To reference temperature ing water supply during the months of freezing. vu velocity $Q LQWDNH PRGLÂżFDWLRQ EDVHG RQ GLVWULEXWLQJ WKH Ă&#x20AC;RZ WR UHGXFH surface velocities and eliminating some vanes was proposed. Nu- u the velocity normal to the trash racks merical results indicate that including pipe openings in the existing trash rack volume walls results in less ice attraction to the intake and longer time before V blockage. The difference in intake operation time when removing Vice volume of ice accumulated in the trash rack IRXU GRZQVWUHDP YDQHV LV QRW VLJQLÂżFDQW +RZHYHU LFH SDUWLFOHV X ratio between intake operation times op are less attracted to the intake region when upstream vanes were also removed. A mitigation plan was developed and is currently being imple- *UHHN OHWWHUV PROHFXODU WKHUPDO FRQGXFWLYLW\ PHQWHG 7KH ÂżUVW SKDVH RI WKH SODQ FRQVLVWV RI FRQQHFWLQJ WKH UHWLUHG ÄŽ intake units and the 2B Emergency Booster Pump intake. A second ÄŽ effective thermal conductivity eff SKDVH FRPSULVLQJ WKH UHPRYDO RI ÂżYH YDQHV LQ IURQW RI UHWLUHG XQLWV ÄŽt eddy thermal conductivity ZLOO EH HIIHFWHG DIWHU SKDVH $ ÂżQDO SKDVH LPSOHPHQWHG LI QHFHVÄ° turbulent dissipation rate 36

CTI Journal, Vol. 35, No. 2

Äł

shape factor

Č&#x203A;

turbulent kinetic energy

Č?eff

effective viscosity

Č?

molecular viscosity

Č?t ČĄo CČ? Č&#x203A;2 eddy viscosity Ä° ČĄo

water density at

ÄąK = 1, ÄąÄ° = 1.2 turbulent Prandtl number for k and ÄŽ Äłi

trash rack porosity

Äłs

screen porosity

Subscript b ice particle

$FNQRZOHGJPHQWV The authors would like to acknowledge Marian Muste from IIHR â&#x20AC;&#x201C; Hydroscience & Engineering, Kathy Dober from AEP Engineering Services, Charlie Dannemiller from AEP Region Engineering and Conesville Plant personnel for their valuable contributions to the study.

References [1] Michell, F., Amaya, P., Dannemiller, C., Ettema, R., Muste, M., 2003, â&#x20AC;&#x153;Correcting Sediment Problems at American (OHFWULF 3RZHUÂśV &RQHVYLOOH 3ODQW ,QWDNHÂ´ &RROLQJ 7HFKnology Institute, TP03-13. [2] Muste, M. and Ettema, R., 2000, â&#x20AC;&#x153;River-Sediment Control DW &RQHVYLOOH 6WDWLRQ RQ WKH 0XVNLQJXP 5LYHU 2KLRÂ´ IIHR Report No. 410.

CTI Journal, Vol. 35, No. 2

[3] Shen, H.T., 2010, â&#x20AC;&#x153;Mathematical Modeling of River Ice 3URFHVVHVÂ´ &ROG 5HJLRQV 6FLHQFH DQG 7HFKQRORJ\ 9RO 62, No.1, pp. 3. [4] Reynolds, O., 1895, "On the Dynamical Theory of Incompressible Viscous Fluids and the Determination of the Criterion", Philosophical Transactions of the Royal Society of London. A, Vol. 186, pp. 123-164. > @ 'DO\ 6 ) Âł)UD]LO ,FH '\QDPLFVÂ´ &ROG 5HJLRQV Research and Engineering Laboratory CRREL Monograph 84-1. [6] Weiss, G.H., 1994, â&#x20AC;&#x153;Aspects and Applications of the 5DQGRP :DONÂ´ 1RUWK +ROODQG 3UHVV $PVWHUGDP 7KH Netherlands. > @ :LOOLDPV * 3 Âł+HDW 7UDQVIHU &RHIÂżFLHQWV IRU 1DWXUDO :DWHU 6XUIDFHVÂ´ 1DWLRQDO 5HVHDUFK &RXQFLO &DQDGD Division of Building Research, 62, pp. 203-212. [8] Su, J., Shen, H.T., Crissman, R.D., 1997, â&#x20AC;&#x153;Numerical Study on Ice Transport in Vicinity of Niagara River Hydropower ,QWDNHVÂ´ -RXUQDO RI &ROG 5HJLRQV (QJLQHHULQJ 9RO 1R 4, pp. 255 (1997). [9] Daly, S.F., Arcone, S.A., 1989, â&#x20AC;&#x153;Airborne Radar Survey RI D %UDVK ,FH -DP LQ WKH 6W &ODLU 5LYHUÂ´ &ROG 5HJLRQV Research and Engineering Laboratory. CRREL Report No. 89-2. [10] Tuthill, A., Liu, L.W., Shen, H.T., 2004, â&#x20AC;&#x153;Modeling Ice 3DVVDJH DW 1DYLJDWLRQ /RFNVÂ´ -RXUQDO RI &ROG 5HJLRQV Engineering Vol. 18, No. 3, pp. 89. [11] Odgaard J., 2009, â&#x20AC;&#x153;River Training and Sediment ManagePHQW ZLWK 6XEPHUJHG 9DQHVÂ´ $6&(

Composite Materials Selection for Structures in Seismic Regions materials energy absorption per unit of volume is

Andrew Green, Andrey Beyle

equal to

Role of Mass of the Structure Damaging and/or catastrophic effects resulting from earthquakes within an active seismic zone are directly proportional to the total mass of the VWUXFWXUH EXLOW ZLWKLQ WKH FRQÂżQHV RI PHQWLRQHG zone. Thus, using of materials with lower densities and stiffer and stronger than the traditional materials (what allows to decrease cross-sectional areas) has to be the priority in the materials selection for the structures built in the seismic zone.

but for ideally plastic

materials it is equal to Â&#x161;Ä°ult. For majority of materials the energy absorption per unit of volume is k Â&#x161;Ä°ult ZKHUH FRHIÂżFLHQW N LV FKDUDFWHUL]HG WKH shape of the stress-strain diagram and which in majority of cases has the value between Â˝ and 1. Energy absorption per unit of mass is determined by

. Some examples of these characteris-

tics for several materials are given in the table, ZKHUH SURSHUWLHV RI UHLQIRUFLQJ ÂżEHUV DUH FRPSDUHG with average properties of the highest grades of VWHHO 3URSHUWLHV RI FRPSRVLWHV GHSHQG RQ VHOHFWHG ÂżEHU DUFKLWHFWXUH It should be noted that for unidirectional composites the effective SURSHUWLHV LQ GLUHFWLRQ RI ÂżEHUV DUH DERXW RI SURSHUWLHV RI UHLQIRUFLQJ ÂżEHUV

$QGUHZ *UHHQ

Critical Parameters The total weight of structure is determined by densities ČĄ of materials and by cross-sectional areas of elements A, which are inverse proportional to the strength Â&#x161; of the materials. As a result, the total weight of the structure is proportional to the ratio ČĄ Â&#x161; or inverse proportional to the ratio Â&#x161; ČĄ 7KH ÂżUVW WDVN RI WKH GHVLJQ IRU D VWUXFWXUH in a seismic area is to decrease the weight of the structure. Structural PHPEHUV PDGH IURP FRPSRVLWHV KDYLQJ VSHFLÂżF VWUHQJWK Â&#x161; ČĄ decimal order higher than the traditional materials are ideal candidates from this point of view (see Table 1). Not only is a decrease of the total mass of a structure important, but so too is the distribution of itsâ&#x20AC;&#x2122; mass. Current research indicates that the best combination comprises that which incorporates a heavily reinforced foundation in conjunction with a structure made from light-weight materials SURYLGHG WKH Ă&#x20AC;H[LEOH UHVSRQVH RQ VXGGHQ ORDGV 7DQWDPRXQW WR these requirements is the necessity to establish a strong connection between the structure and its foundation.

Table 1.

Flexural vibrations of the structure depend on the parameter ZKHUH ( Âą LV WKH <RXQJ PRGXOXV RI PDWHULDO ČŚ Âą LV the frequency of vibrations, J â&#x20AC;&#x201C; is the moment of inertia of the crosssection, and A â&#x20AC;&#x201C; is the cross-sectional area. In regards to improving ability of the structure to withstand seismic stresses this parameter KDV WR EH GHFUHDVHG 7KH VSHFLÂżF VWLIIQHVV ( ČĄ of composites (which is participating in the denominator of the parameter ÄŽ) is much higher than in traditional materials and as a result their vibrational performance is better. Energy absorption is the key characteristic of any structure in dynamic loading. Energy absorption ability of material is mainly GHWHUPLQHG E\ WKH ÂłDUHD XQGHU VWUHVV VWUDLQ FXUYHÂ´ 6RPHWLPHV WKLV FKDUDFWHULVWLF LV FDOOHG ÂłPDWHULDO WRXJKQHVVÂ´ +RZHYHU LW FUHDWHV D FRQIXVLRQ ZLWK HVWDEOLVKHG WHUPLQXV ÂłIUDFWXUH WRXJKQHVVÂ´ FKDUDFterizing resistance to the crack propagation. It should be noted that the strong but brittle material can absorb much less energy than not so strong materials with greater ultimate strain. For linearly elastic 38

Structures manufactured from high grades of armor steel absorb a lot of energy per unit of volume due to their combination of high strength and plasticity. However, composites are replacing steel even LQ VXFK WUDGLWLRQDO G\QDPLF DSSOLFDWLRQV VXFK DV DUPRXUHG ÂżJKWLQJ machines and military tanks armor because composites have better energy absorption per unit of mass. Other important characteristics VXFK DV VSHFLÂżF VWUHQJWK DQG VSHFLÂżF VWLIIQHVV DUH PXFK KLJKHU LQ composites than in steel. Comparison of the stress-strain diagrams of different materials is shown in the Fig. 1.

$GGLWLRQDO 3URSHUWLHV ,PSRUWDQW IRU '\QDPLF $SSOLFDWLRQV The key to success in the design of structures for dynamic applications is the ability to redistribute the peak of stresses in the time and in the constituentsâ&#x20AC;&#x2122; area/space. Reaction on suddenly applied ORDG LV EHWWHU LI VWUXFWXUH LV PRUH Ă&#x20AC;H[LEOH VHH )LJ ,W DOORZV UHdistributing stress peak in time, decreasing the maximal stress, and avoiding the fracture. This is well known from an observation of CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

5HVLVWDQFH WR WKH &UDFN 3URSDJDWLRQ There are other characteristics of materials to take into account. Fracture toughness and ductility are important also, however, there DUH GLIIHUHQW FRQFHSWV KLGGHQ XQGHU WKHVH WHUPV - LQWHJUDO VWUHVV LQWHQVLW\ IDFWRU FUDFN H[WHQVLRQ IRUFH HWF 'HSHQGLQJ RQ ÂżEHU architecture, the resistance of composites to the crack propagation FDQ YDU\ LQ ZLGH UDQJHV :KHQ ELJJHU QXPEHU RI ÂżEHUV WKH FUDFN needs to cut in the process of its propagation, the higher fracture toughness of composite is observed. Figure 1. Stress-strain diagrams of different reinforcements PDWHULDOV VWHHO WZR JUDGHV JODVV ÂżEHU UHLQIRUFHG SODVWLFV ZLWK ( JODVV ÂżEHUV DQG E\ 6 JODVV ÂżEHUV SHU YROXPH RI FRPSRVLWH DQG FDUERQ ÂżEHUV UHLQIRUFHG SODVWLFV KLJK VWUHQJWK Torayca T1000 and high modulus Torayca 0 - ÂżEHUV SHU YROXPH

$ERXW 8VH 2I &RQFUHWH ,Q 6HLVPLF $UHDV

Concrete is used in dynamic applications such as protective bunkers against artillery shells and bombs. However, its application in seismic areas has to be done with some precautions. Concrete has relatively high compressive strength and low tensile strength. As a result, because the pure shear can be represented as a combination of ÂżVKLQJ URGV EHKDYLRU $OVR EHFDXVH VXGGHQ ORDG LV DSSOLHG RQ VRPH tension in one diagonal direction and compression in other diagonal part of the structure surface not in the whole volume of structure, direction, the resistance of concrete to pure shear is very low too. the ability to involve as much material as possible in the resistance When shear is acting simultaneously with hydrostatic pressure, the and as quick as possible provides opportunity to avoid sharp peaks UHVLVWDQFH RI FRQFUHWH LV LQFUHDVLQJ VLJQLÂżFDQWO\ 7KLV LGHD LV XVHG of the stresses. The velocities of the elastic waves are proportional in dome-shaped bunkers. However, the pure shear is one of the WR WKH VTXDUH URRW IURP WKH VSHFLÂżF VWLIIQHVV (YHQ LQ JODVV ÂżEHUV most typical seismic stresses. It means that concrete has to be not the velocity of the elastic waves is higher than in steel, in Kevlar only reinforced but also well-pre-stressed. Using composites for LW LV WLPHV KLJKHU LQ FDUERQ ÂżEHUV LW LV XS WR WLPHV KLJKHU reinforcement of concrete was the subject of investigations during Materials with higher elastic speed velocities are preferable for ODVW VL[W\ \HDUV ,QLWLDOO\ WKHUH ZHUH UHEDUV PDGH IURP JODVV ÂżEHU dynamic applications. UHLQIRUFHG SODVWLF 7KHVH UHEDUV KDYH KLJK VWUHQJWK EXW LQVXIÂżFLHQW stiffness. As a result, it is necessary to use much bigger volume concentration of the reinforcement in comparison with steel rebars. However, for the high level of pre-stress of the concrete, the JODVV ÂżEHU UHLQIRUFHG SODVWLFV DUH SUHIHUDEOH LQ FRPSDULVRQ ZLWK steel because the maximal elastic strain is much higher in glass ÂżEHUV WKDQ LQ VWHHO &DUERQ ÂżEHU UHLQIRUFHG SODVWLFV KDYLQJ KLJKHU strength and stiffness than steel are much more expensive than the JODVV ÂżEHU UHLQIRUFHG SODVWLFV 'HVSLWH WKLV UHVWULFWLRQ FDUERQ ÂżEHU reinforced plastics are used more and more for reinforcing concrete in unique structures. There are some problems with secure gripping composite rebars in concrete until complete fracture of the material with static fatigue of rebars, etc. Nevertheless, more and more composite rebars are used for concrete now and their much bigger role in the reinforced concrete structures for seismic areas is expected.

&RROLQJ 7RZHUV )RU 7KH 6HLVPLF $UHDV Application of composites for cooling towers structures was started E\ WKH ÂżUVW DXWKRU RI WKLV UHSRUW ZLWK WKH ÂżUP &HUDPLF &RROLQJ 7RZBesides energy absorption, the energy dissipation is extremely ers Inc. (Fort Worth). Now the Composite Cooling Solutions Inc. important in reaction of the structure on suddenly applied loads. constructs cooling towers from composites on regular basis. These Whole absorbed energy can be subdivided to stored energy and to types of the structures are more appropriate for the seismic areas dissipated energy. The ratio of dissipated energy to stored energy than the traditional ones. However, there are some adjustments in the LQ WKH PDWHULDO LV FDOOHG ÂłWDQJHQW GHOWDÂ´ EHFDXVH LW LV VWXGLHG H[- GHVLJQ KDV WR EH PDGH VSHFLÂżFDOO\ WDUJHWLQJ VWUXFWXUH SHUIRUPDQFH perimentally in cyclic loading and is determined via phase shift XQGHU VHLVPLF ORDGV )DQ EODGHV YLEUDWLRQ GXH WR SRVVLEOH GHĂ&#x20AC;HFbetween load and displacement). In steel the energy dissipation tions of the axis of the rotation during seismic activity is an example is related to the plastic deformation. In composites the energy of the problem to be solved. Composite Cooling Solutions Inc. is dissipation happens due to viscoelastic deformation of polymeric collaborating with Lamar University (Beaumont, TX) in research PDWUL[ $OVR SRO\PHULF ÂżEHUV VXFK DV .HYODU 6SHFWUD =\ORQ DUH and development. characterized by nonlinear viscoelasticity. Spectrum of relaxation times in polymers is very wide. From one side, it results in creep in Conclusions long-time loading. From another side, in very short time dynamic Authors experience in such structures as racing cars (Chaparral) processes part of energy dissipates and as a result, the peak stress is or commercial cars (springs for Corvette and Camaro), helicopter much lower than in the case of absence of energy dissipation. This EODGHV DOO FRPSRVLWH EXLOGLQJV $SSOH $7 7 EULGJHV ÂżVKLQJ is the second mechanism of the stress redistribution during the time. rods, yachts, airspace and other structures (Green), in airspace, ,W LV WKH UHDVRQ ZK\ .HYODU ÂżEHUV DUH PRUH HIIHFWLYH LQ EXOOHW SURRI electrical machinery, shipbuilding, wind turbines, and defense YHVWV WKDQ WKH FDUERQ ÂżEHUV GHVSLWH WKH PHFKDQLFDO FKDUDFWHULVWLFV (blast-resistant structures) (Beyle) is convincing that the composites are the exceptional materials for cooling tower construction in RI FDUERQ ÂżEHUV DUH EHWWHU WKDQ LQ .HYODU ÂżEHUV seismic zones. Figure 2. Schematic comparison of the reaction on suddenly applied load in two types of structures.

CTI Journal, Vol. 35, No. 2

Lessons Learned from a High Recovery RO - Based ZLD System Now, increasingly stringent air quality regulations and the availability of cheap natural gas have led WR VLJQLÂżFDQW JURZWK RI VLPSOH DQG HVSHFLDOO\ combined-cycle units for new power generation. But due to pending 316b water regulations, which are designed to protect marine life from destruction in cooling water intakes, virtually all new FRPELQHG F\FOH SURMHFW VSHFLÂżFDWLRQV FDOO IRU D cooling tower, or in some instances an air-cooled condenser. Complicating these developments is that NPDES guidelines are tightening, but not necessarily in a uniform manner.

Brad Buecker Kiewit Power Engineers

A critical topic that continues to be discussed at CTI meetings is the need for water conservation across a broad spectrum of industries and municipal applications. Major contributing factors in many cases are increasingly stringent wastewater discharge regulations, as outlined in this paper. More and more, plant personnel are looking at cooling tower blowdown recycle and recovery as a method to conserve water, with the ultimate scenario being zero liquid discharge (ZLD). An emerging technology The EPA is currently preparing new national guide%UDG %XHFNHU is water recovery based on high-recovery reverse lines that will place limits on additional power RVPRVLV WHFKQRORJ\ 7KLV SURFHVV LQFOXGHV XOWUDÂżOWUDWLRQ VRIWHQLQJ plant cooling tower blowdown constituents. [1] These include the and reverse osmosis. However, the concentrating nature of cool- heavy metals chromium and zinc, with projected limits of 0.2 and ing towers combined with chemical treatment programs subjects 1 part-per-million (ppm), respectively. However, some individual EORZGRZQ WUHDWPHQW V\VWHPV WR FKHPLVWU\ WKDW PD\ VLJQLÂżFDQWO\ state regulators have begun to place limits on some or all of the LQĂ&#x20AC;XHQFH SHUIRUPDQFH 7KH ÂżQDO VHFWLRQV RI WKLV SDSHU H[DPLQH IROORZLQJ DGGLWLRQDO FRQVWLWXHQWV lessons learned from actual operation at an existing power plant. Â&#x2021; Total dissolved solids (TDS) 'LIÂżFXOWLHV LQFOXGHG SRRU SHUIRUPDQFH RI DQ XSVWUHDP PXOWL PHGLD Â&#x2021; Sulfate ÂżOWHU IRXOLQJ RI XOWUDÂżOWHU PHPEUDQHV IURP VWDQGDUG FRROLQJ WRZHU treatment chemicals, and the somewhat belated realization that feed Â&#x2021; Copper of a cationic polymer ahead of membrane systems is typically not Â&#x2021; Phosphate a good idea. Â&#x2021; Ammonia

Increasingly Strict Regulations for Cooling Tower Blowdown

Subsequent to the passage of the Clean Water Act in the late 1960s, the U.S. Environmental Protection Agency (EPA) began controlling industrial plant wastewater discharges per National Pollutant Discharge Elimination System (NPDES) guidelines. In many cases, NPDES guidelines focused upon a small core of primary impurities in wastewater discharge streams. These included total suspended solids (TSS), oil and grease (O&G), pH, and free chlorine (or other oxidizing biocide). A once-common guideline is shown below in abbreviated form.

Â&#x2021;

Quantity of discharge

Concurrently, regulators are pushing some plants to use alternatives to fresh water for makeup. (This trend is particularly evident in California.) These sources include reclaim water from municipal wastewater treatment plants and poorquality groundwater. In the case of the former, ammonia and phosphate are often problematic constituents, and thus the cooling tower makeup might require treatment such as ammonia stripping and phosphate precipitation E\ FODULÂżFDWLRQ WR SURWHFW WKH GLVFKDUJH *URXQGZDWHU PD\ FRQWDLQ high concentrations of hardness, alkalinity, chlorides and sulfates, and silica.

As an example of changing NPDES regulations, consider the new guidelines at a power plant in one of our southern states, where cooling tower blowdown constitutes nearly all of the plantâ&#x20AC;&#x2122;s liquid discharge. Prior to 2013, the plantâ&#x20AC;&#x2122;s NPDES permit primarily 7DEOH Âą $Q $EEUHYLDWHG 13'(6 ([DPSOH focused upon the items outlined in Table 1. The new permit now At many plants constructed in the previous century, once-through imposes an average monthly limit of 1,200 mg/l TDS. Given that cooling systems were common, and these limits were often easy to the makeup water TDS concentration sometimes reaches 400 mg/l DFKLHYH 7KH PDMRULW\ RI SUREOHPV DURVH DW FRDO ÂżUHG SRZHU SODQWV TDS, the tower cycles of concentration (COC) may be limited to from impurities in the discharge of coal pile runoff ponds and wet three under the new regulations, whereas previously the tower had ash disposal ponds. The constituents in these particular streams EHHQ RSHUDWHG DW D VLJQLÂżFDQWO\ KLJKHU &2& that required the most oversight tended to be TSS and pH, but Another impurity receiving more scrutiny is sulfate (SO4). This isstraightforward methods were available to control this chemistry. sue can be problematic with regard to process chemistry, as sulfuric 42

CTI Journal, Vol. 35, No. 2

acid feed to cooling tower makeup has been a common method to remove bicarbonate alkalinity and thus minimize calcium carbonate (CaCO3) scaling in the condenser and cooling system. H2SO4 + Ca(HCO3)2)Äş &D624 + 2H2O + 2CO2Äš Tighter regulations on sulfate in the discharge stream may curtail or eliminate this straightforward method of scale control at some plants. ,QGHHG DW WKH SODQW RXWOLQHG LQ WKLV ÂżUVW FDVH KLVWRU\ WKH QHZ JXLGHline limits the sulfate concentration to 400 mg/l. Also as touched upon above, phosphate is being banned in some waste streams. [2] Phosphate serves as a primary nutrient for plant growth, and when released to open bodies of water can often initiate and propagate DOJDH EORRPV 7KH GLIÂżFXOW\ LV WKDW D YHU\ FRPPRQ FRROLQJ WRZHU treatment method relies on the use of organic and inorganic phosphates for corrosion and scale control. New, all-polymer programs are emerging to minimize phosphate use.

sites strategically located is to have the wastewater trucked off-site to a waste disposal company. But this technique can be expensive because obviously the vast bulk of the material is simply water, and also because waste remediation is high-priced commodity. If none of the above options are acceptlable, thermal evaporation of the waste stream may be the only choice. At a recent visit to a plant in the southwestern U.S., the author observed a brine concentrator/ crystallizer system that treats the entire cooling tower discharge. :KLOH WKH V\VWHP LV UHOLDEOH WKH LQOHW Ă&#x20AC;RZ UDWH DW IXOO ORDG LV QHDUO\ 1000 gpm. Thus, energy requirements are quite large, as are the regular maintenance costs to remove accumulated solids from the evaporation equipment. For these reasons, becoming popular are treatment methods to UHGXFH WKH YROXPH RI WKH SODQW ZDVWH VWUHDP EHIRUH ÂżQDO WUHDWPHQW A notable example is high-recovery reverse osmosis, as outlined generically below.

As has been noted, zinc and chromium are on the proposed new NPDES list. State regulations may be more comprehensive or stringent with regard to metals discharge. For the power plant mentioned above, in 2015 copper will be incorporated into the discharge guidelines, where the limit will be less than 30 parts-perbillion (ppb). Some plants in the country have even lower copper discharge guidelines. At these very low limits, copper discharge can potentially be a problem from units equipped with copper-alloy condenser tubes. However, another copper source, sometimes from older wooden cooling towers, comes from copper compounds utilized as a wood preservative. One possible solution is replacement )LJ *HQHULF RXWOLQH RI DQ HPHUJLQJ RI WKH ROG FRROLQJ WRZHU ZLWK D PRGHUQ ÂżEHUJODVV WRZHU $QRWKHU wastewater treatment technology. possibility is installation of a wastewater treatment plant with a .H\V WR WKH SURFHVV DUH heavy metal precipitation process. Â&#x2021; 0LFURÂżOWUDWLRQ 0) RU XOWUDÂżOWUDWLRQ 8) WR UHPRYH The upshot of this discussion is that at existing plants costs to suspended solids in the waste stream. This is a critical FRPSO\ ZLWK QHZ OLTXLG HIĂ&#x20AC;XHQW JXLGHOLQHV PD\ EH VLJQLÂżFDQW $ process to prevent suspended solids from fouling reverse switch to all-polymer chemistry in a large cooling tower to eliminate osmosis (RO) membranes. SKRVSKDWH LQ WKH GLVFKDUJH PD\ UHVXOW LQ VLJQLÂżFDQW DQQXDO 2 0 Â&#x2021; 6RGLXP ELVXOÂżWH 1D+623) feed to remove residual oxicost increases. Alternatively, the capital cost for installation of a dizing biocides. This is also critical to remove oxidizing treatment system to remove newly-regulated impurities from the biocides that would degrade softener resin and RO memdischarge stream may reach or exceed one million dollars. Plus, a branes. waste treatment system adds complexity and operational costs of its own to the plant. Â&#x2021; A sodium softener to remove calcium and magnesium. Otherwise the downstream equipment would suffer from Moving to ZLD calcium carbonate and magnesium silicate scaling. In addition to the impurities mentioned above, there is every posÂ&#x2021; Sodium hydroxide injection to elevate the pH above 10. sibility that additional wastewater contaminants may be regulated (The combination of hardness removal and pH elevation in the future. For this reason, some experts recommend that plants keeps silica in solution.) consider ZLD at the very beginning of the project. This process is Â&#x2021; Two-pass reverse osmosis (RO) treatment. often rather complex. Perhaps the most straightforward disposal technique, but with a large caveat, is deep well injection. The wells Under proper conditions, a 90-percent RO recovery rate is possible. may be several thousand feet deep to avoid any discharge into shal- The RO permeate recycles to the plant high-purity makeup water low groundwater used for domestic purposes. While this concept system or other locations. However, while the process appears sounds simple, experience has shown that some wastewaters can straightforward, a number of lessons-learned have emerged regardgenerate scale within the well shaft, particularly as the water warms ing this technology in actual application. The following lessons are further underground. High-pressure is generally required for this taken from a high-recovery RO system operating at a power plant process, and if scale formation occurs, capacity may decrease. LQ WKH 3DFLÂżF 1RUWKZHVW 2QH RI WKH PRVW QRWDEOH LV WKDW VRPH At plants in arid locations with a large land area, evaporation ponds PD\ EH VXIÂżFLHQW WR KDQGOH WKH ZDVWHZDWHU GLVFKDUJH +RZHYHU these ponds must be properly lined to prevent seepage of the wastewater with its impurities into the underlying soil. Permitting may or may not be granted for evaporation ponds. Another alternative at

standard water treatment chemicals may foul the UF membranes. Operating experience indicates that the membrane manufacturer and W\SH JUHDWO\ LQĂ&#x20AC;XHQFH WKLV SKHQRPHQRQ )RXOLQJ PD\ EH FDXVHG E\ the fact that most membranes carry a negative surface charge while FDWLRQLF SRO\PHUV DUH XVXDOO\ HPSOR\HG IRU Ă&#x20AC;RFFXODWLRQ 5HVLGXDO CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

polymer will coat the membranes. (A very similar phenomenon has been observed with MF or UF systems installed in makeup water V\VWHPV GRZQVWUHDP RI D FODULÂżHU ,QH[SHULHQFHG GHVLJQHUV DQG RU plant personnel have not always recognized that MF or UF should JHQHUDOO\ VHUYH DV D UHSODFHPHQW IRU FODULÂżFDWLRQ QRW D SROLVKLQJ SURFHVV IRU WKH FODULÂżHU

$ VWUDLJKWIRUZDUG VROXWLRQ WKDW KDV VLJQLÂżFDQWO\ LPSURYHG WKH UHOLDELOLW\ RI WKLV SDUWLFXODU V\VWHP LV FRQYHUVLRQ RI WKH XOWUDÂżOWHU IURP DQ LQVLGH RXW SURFHVV Ă&#x20AC;RZ SDWK WR RXWVLGH LQ 7\SLFDO PLFUR DQG XOWUDÂżOWHU V\VWHPV FRQVLVW RI PXOWLSOH SDUDOOHO Ă&#x20AC;RZ PRGXOHV FRQWDLQLQJ WKRXVDQGV RI VSDJKHWWL OLNH KROORZ ÂżEHU PHPEUDQHV

LQMHFWLRQ WR ORZHU WKH S+ ZDV QRW WKDW VLPSOH 7KH RULJLQDO FRQÂżJXration had direct sulfuric acid injection into the discharge pipe via a basic mixing tee. However, concentrated sulfuric acid is a viscous OLTXLG WKDW WDNHV VRPH WLPH WR GLVVROYH 5HVLGXDO DFLG Ă&#x20AC;RZLQJ DORQJ WKH SLSH ZDOO GRZQVWUHDP RI WKH PL[LQJ WHH KDV FDXVHG VLJQLÂżFDQW corrosion of the discharge pipe. A re-design of the neutralization process is currently underway. The upshot of this case history is that pilot testing with the proposed cooling tower chemistry is very important for analyzing membrane performance. Some water treatment equipment vendors have sugJHVWHG XSVWUHDP PXOWL PHGLD ÂżOWHUV WR KHOS UHPRYH WKH FKHPLFDOV from the blowdown stream, but direct observation has shown that WKHVH ÂżOWHUV PD\ EH LQHIIHFWLYH LQ SUHYHQWLQJ FKHPLFDO IRXOLQJ RI membranes. An important factor in general with these systems regards redundancy, either via storage capacity or standby equipment. With a SURSHUO\ RSHUDWLQJ V\VWHP WKH ÂżQDO ZDVWH VWUHDP LV REYLRXVO\ YHU\ much reduced. But if the system comes off line, the entire blowdown DQG DGGLWLRQDO SODQW ZDVWHZDWHU VWUHDPV FDQ EH WRR WD[LQJ IRU WKH Âżnal treatment process, particularly if it involves thermal evaporation.

$ 3RWHQWLDO 5HFODLP :DWHU 6FHQDULR Very recently, the author became involved in a project where reclaim water will be used as the makeup to a power plant cooling tower, but where the entire blowdown will be recycled to the wastewater treatment plant. Another plant in the area is already doing so.

)LJ $ FXW DZD\ YLHZ RI D KROORZ ÂżEHU PLFURÂżOWHU SUHVVXUH YHVVHO VKRZLQJ WKH KROORZ ÂżEHU PHPEUDQHV

The membranes must be regularly backwashed every 10 to 20 PLQXWHV RU WKHUHDERXWV WR UHPRYH SDUWLFXODWHV 7KH EDFNZDVK Ă&#x20AC;RZ SDWK LV WKH UHYHUVH RI WKH QRUPDO Ă&#x20AC;RZ SDWK ,Q WKLV FDVH FRQYHUVLRQ RI WKH PHPEUDQHV IURP LQVLGH RXW WR RXWVLGH LQ QRUPDO Ă&#x20AC;RZ SDWK KDV VLJQLÂżFDQWO\ LPSURYHG WKH EDFNZDVK HIÂżFLHQF\ SHUKDSV GXH WR greater ability for the supplemental air scour to better contact the membrane surfaces. $QRWKHU LQWHUHVWLQJ LQLWLDO GLIÂżFXOW\ ZDV QRWHG ZLWK WKH 8) EDFNZDVK process. Typically with these systems, a small portion of the permeate is collected in a separate tank at the beginning of each process cycle for use in backwash. So far, so good. But most modern MF and UF units are now equipped with automatic chemically-enhanced backwash (CEB) systems. After a certain number of cycles, a CEB EDFNZDVK NLFNV LQ ZKHUH ÂżUVW WKH PHPEUDQHV DUH FOHDQHG ZLWK D dilute caustic/bleach solution to remove organics and microbiological organisms, followed by rinsing and then a dilute citric acid ZDVK WR UHPRYH LURQ SDUWLFXODWHV :KHQ WKLV SDUWLFXODU 8) ZDV ÂżUVW commissioned, the membranes developed a layer of calcium silicate )LJ 5HFODLP PDNHXS WR D FRROLQJ WRZHU during the CEB caustic stage. The driving force was the higher pH ZLWK DOO EORZGRZQ UHWXUQHG WR WKH ::73 generated by the caustic, which in turn greatly reduced the silicate solubility. The solution to this problem was a switch to softened $W ÂżUVW JODQFH WKH QDWXUDO LQFOLQDWLRQ LV WR EHOLHYH WKDW FRPSOHWH blowdown recovery would cause a continual increase in solids water for the backwash supply. within the system. However, if one examines this schematic using Yet another lesson learned from this application involved treatment a control volume diagram, the issue becomes clear. of the reject stream from the RO unit. It has an elevated pH due WR WKH FDXVWLF LQMHFWLRQ IRU VLOLFDWH VFDOH FRQWURO EXW ÂłVLPSOHÂ´ DFLG

CTI Journal, Vol. 35, No. 2

salts and heavy metals. The author has heard recent comments that chloride and bromide concentrations may be limited in some plant discharges. Selection of ZLD as a proactive measure can prepare a plant for future eventualities. Â&#x2021;

Â&#x2021; 9DULDEOH LQĂ&#x20AC;XHQW ZDWHU TXDOLW\ SDUWLFXODUO\ LI WKH SODQW makeup quality is inconsistent. Â&#x2021; Potential for fouling of the wastewater treatment system from some chemicals utilized for cooling water treatment. Â&#x2021; &KDQJH RI LQĂ&#x20AC;XHQW Ă&#x20AC;RZ UDWH GXH WR D FKDQJH LQ FRROLQJ WRZHU F\FOHV RI FRQFHQWUDWLRQ SHU FKHPLVWU\ PRGLÂżFDtions. Â&#x2021; 'HDOLQJ ZLWK WKH ÂżQDO ZDVWH VWUHDP WKDW FRPHV IURP WKH primary treatment process. If techniques such as evaporation ponds or deep-well injection are not possible, thermal evaporation may be the only choice.

)LJ 7KH Ă&#x20AC;RZ VFKHPDWLF ZLWK D FRQWURO YROXPH ERXQGDU\

The recycle of blowdown is an internal process, and after startup of the system as the blowdown solids concentration increases, at a certain point the amount of solids exiting the process balances the amount entering. The author has prepared an iterative program in Excel that demonstrates this calculation. It should be noted that a blowdown treatment system, perhaps a lime softener, may be needed to prevent excess accumulation of scale-forming solids in the WWTP. Such a system, with equipment to generate a solid sludge, can establish ZLD conditions.

Summary Once-through cooling is no longer an option for new power plants. In many cases, cooling towers are the preferred choice, although air-cooled condensers are appearing more frequently. For new and H[LVWLQJ SODQWV ZLWK FRROLQJ WRZHUV LQFUHDVLQJO\ VWULQJHQW HIĂ&#x20AC;XHQW guidelines are requiring plant owners, operators, and technical SHUVRQQHO WR HYDOXDWH ZDWHU DQG ZDVWHZDWHU WUHDWPHQW PRGLÂżFDWLRQV DQG DGGLWLRQV 0DQ\ IDFWRUV DUH LQĂ&#x20AC;XHQFLQJ WKHVH GHFLVLRQV DQG WKH\ LQFOXGH

Â&#x2021;

States may impose guidelines beyond those of the USEPA.

Â&#x2021;

Regulations are appearing for such wastewater constituents as total dissolved solids, sulfate, phosphate, ammonia, and some heavy metals.

Â&#x2021;

Restrictions on discharge of some of these impurities, VXFK DV SKRVSKDWH FDQ JUHDWO\ LQĂ&#x20AC;XHQFH WKH FKRLFH RI cooling tower treatment program. All-polymer programs are emerging.

Â&#x2021;

Discharge chemistry control may, in part at least, have to EH DGGUHVVHG E\ PRGLÂżFDWLRQV WR PDNHXS ZDWHU WUHDWPHQW

Â&#x2021;

Increasingly, plants in some areas of the country, either from mandate or necessity, are selecting reclaim (gray) water for makeup. These supplies often have quite variDEOH ZDWHU TXDOLW\ ZKLFK JUHDWO\ LQĂ&#x20AC;XHQFHV FRROLQJ WRZHU operation and blowdown chemistry.

Â&#x2021;

Installation of wastewater treatment systems may be required to comply with new guidelines.

Â&#x2021;

It is quite possible that other wastewater constituents may be regulated in the future. These might include additional

Installation and operation of a wastewater treatment system up to ZLD is not a simple process. Many factors can LQĂ&#x20AC;XHQFH V\VWHP SHUIRUPDQFH LQFOXGLQJ

References 1.

Federal Register, Vol. 78, No. 110, 40 CFR Part 423, Âł(IĂ&#x20AC;XHQW /LPLWDWLRQV *XLGHOLQHV DQG 6WDQGDUGV IRU WKH Steam Electric Power Generating Point Source Category; 3URSRVHG 5XOHÂ´ (QYLURQPHQWDO 3URWHFWLRQ $JHQF\ -XQH 7, 2013.

Post, R. and B. Buecker, â&#x20AC;&#x153;Power Plant Cooling Water FunGDPHQWDOVÂ´ SUH FRQIHUHQFH VHPLQDU IRU WKH UG $QQXDO Electric Utility Chemistry Workshop, June 11-13, 2013, Champaign, Illinois.

Brad Buecker is a Process Specialist with Kiewit Power Engineers, Lenexa, KS. He has over 33 years of experience in the power indusWU\ PXFK RI LW ZLWK &LW\ :DWHU /LJKW 3RZHU LQ 6SULQJÂżHOG ,/ DQG at Kansas City Power & Light Companyâ&#x20AC;&#x2122;s La Cygne, KS generating station. Buecker has written many articles and three books on steam generation topics, and he is a member of the American Chemical Society, the American Institute of Chemical Engineers, the American Society of Mechanical Engineers, the Cooling Technology Institute, and the National Association of Corrosion Engineers. He has a B.S. in chemistry from Iowa State University, with additional course ZRUN LQ Ă&#x20AC;XLG PHFKDQLFV KHDW DQG PDWHULDO EDODQFHV DQG DGYDQFHG inorganic chemistry.

CTI Journal, Vol. 35, No. 2

'HYHORSPHQW DQG $SSOLFDWLRQ RI 3KRVSKRUXV )UHH &RROLQJ :DWHU Technology Raymond M. Post, ChemTreat Richard Tribble, ChemTreat Prasad Kalakodimi, ChemTreat

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WR WKH SUHYDOHQFH RI KLJK WHPSHUDWXUH ORZ Ă&#x20AC;RZ bundles together with steel piping operating at much lower temperature. Apart from unforgiving control requirements, phosphate has several additional weaknesses. Phosphate by itself is an effective inhibitor only for steel and a marginal inhibitor for galvanized VXUIDFHV ,W KDV OLWWOH RU QR EHQHÂżFLDO HIIHFW on copper or aluminum corrosion. Phosphate programs often perform poorly in soft or low hardness waters, requiring much higher levels of phosphate to form an effective calcium SKRVSKDWH ÂżOP 3KRVSKDWH ZLOO DOVR SUHFLSLWDWH ZLWK ZHOO ZDWHU LURQ DQG DOXPLQXP FODULÂżHU FDUryover, forming deposits and causing excessive polymeric dispersant demand.

Phosphate based corrosion and scale inhibitor programs emerged as the cooling water treatment technology of choice when the industry was strongly encouraged to eliminate chromates some 35 years ago. At that time, we were certainly aware of the many troublesome issues associated with SKRVSKRUXV EDVHG SURJUDPV WKH SUHFLVH FRQWURO required to prevent phosphate deposits on hot bundles, inadequate admiralty brass corrosion using only azoles, escalating dispersant demand due to phosphate precipitation with well water iron and Raymond M. Post aluminum carryover, and excessive algae growth on Emerging Phosphorus the towers and the associated chlorine demand. Although we were Regulations aware of impending phosphorus regulations we continued to perfect phosphorus based cooling water programs because there simply Recently, US regulations have begun to restrict the industrial diswas no reasonable alternative â&#x20AC;Ś.until now. This paper describes charge of phosphorus as an undesirable aquatic nutrient for cyanothe development of a promising phosphorus free corrosion and bacteria and algae in the environment. Controlling algae growth GHSRVLW FRQWURO SURJUDP LQFOXGLQJ ODERUDWRU\ DQG ÂżHOG DSSOLFDWLRQ by restricting phosphorus can be traced to Justus Von Liebig, a 19th century German chemist considered to be the â&#x20AC;&#x153;father of the fertilizer performance data from several challenging applications. LQGXVWU\Â´ +H LV FUHGLWHG ZLWK SRSXODUL]LQJ /LHELJÂśV Âł/DZ RI WKH %DFNJURXQG 0LQLPXPÂ´ ZKLFK VWDWHV WKDW JURZWK LV FRQWUROOHG QRW E\ WKH WRWDO Cooling water treatment from the 1930s through the early 1980s amount of resources available, but by the scarcest resource. relied primarily upon 5-500 ppm hexavalent chromium to inhibit Phosphorus is generally the limiting nutrient for cyanobacteria and corrosion of steel and copper alloys in conjunction with acid to algae growth, not only in the environment but also in many cooling maintain the pH of the system in the 6.0-7.0 range to control scale tower systems. Algae and cyanobacteria derive energy from abunformation. In the last decades of the chromate era, zinc and poly- dant sunlight, and carbon for cellular growth from abundant bicarphosphate supplements were added to support lower levels of chro- bonate in the water. Cyanobacteria and many species of algae can mate. Chromate proved to be an excellent steel and copper corrosion ÂłÂż[Â´ DWPRVSKHULF QLWURJHQ LQWR ZDWHU 7KH\ FRORQL]H ZDWHU ERGLHV inhibitor, but its greatest attribute was its forgiving nature. A dosage in thick mats and produce cyanotoxins that are hazardous to aquatic of 50 ppm provided excellent performance and 500 ppm performed PDPPDOV ÂżVK VKHOOÂżVK DQG HYHQ KXPDQV ,Q WKH HQYLURQPHQW WKH even better across the broad pH 6.0-7.0 range. An overfeed did not periodic die-offs of algae and cyanobacteria cause dissolved oxygen lead to fouling, and more corrosive conditions, even brines, could ÂłVDJVÂ´ WKDW DGYHUVHO\ DIIHFW DTXDWLF OLIH $FFRUGLQJ WR 86(3$ always be overcome with higher treatment levels. phosphorus and nitrogen nutrients are the cause of degradation in As chromate was phased out due to human health concerns and KDOI RI LPSDLUHG ZDWHU ERGLHV DQG DUH DVVRFLDWHG ZLWK ÂżVK NLOOV zinc has been mostly phased out due to aquatic toxicity, the cooling sediment accumulation, unhealthful trihalomethanes (THMs) in water treatment industry in the United States and Western Europe chlorinated drinking water, and a 6,000 square mile low dissolved focused primarily on phosphate-based chemistries for both corrosion R[\JHQ ÂłGHDG ]RQHÂ´ LQ WKH 0LVVLVVLSSL 5LYHU GHOWD GUDLQDJH DUHD and scale control. Progressive advances have led to polymers that USEPAâ&#x20AC;&#x2122;s strategy for regulating nutrients under the Clean Water Act DUH PRUH HIÂżFLHQW LQ PDLQWDLQLQJ KLJKHU OHYHOV RI RUWKRSKRVSKDWH is based on the concept of a Total Maximum Daily Load (TMDL) for in solution. Organic phosphate components provide both scale a particular nutrient or pollutant entering a watershed . If a watershed inhibition and cathodic corrosion inhibition for steel. Aromatic is deemed to be impaired, a Waste Load Allocation (WLA) must D]ROH VXSSOHPHQWV DUH XVHG WR RYHUFRPH SKRVSKDWHÂśV GHÂżFLHQF\ LQ be developed for that pollutant which restricts the amount entering protecting copper alloys. the watershed to an amount that is below its assimilative capacity. Todayâ&#x20AC;&#x2122;s phosphate chemistries perform adequately in most circum- At this point in time, an inventory of all the impaired water bodies stances but demand precise control. The concentration of phosphate in the US has been compiled, along with the pollutants responsible must be balanced carefully with calcium, polymeric dispersant, pH, for the impairment. If the watershed is impaired by phosphorus, a DQG WHPSHUDWXUH ,I DOO ÂżYH IDFWRUV DUH QRW SHUIHFWO\ EDODQFHG DW DOO more stringent limit for phosphorus discharge is likely to be incortimes and at all points in the system, either corrosion or fouling will porated into the siteâ&#x20AC;&#x2122;s NPDES permit at the time of renewal. Figure occur. This is particularly problematic in the chemical industry due 1 illustrates this water quality based TMDL approach. 52

CTI Journal, Vol. 35, No. 2

Laboratory Studies Scale Inhibitor Development Organic phosphates have been the primary calcium carbonate scale inhibitors used by the industry since the mid-1970â&#x20AC;&#x2122;s. They also serve an additional role as cathodic corrosion inhibitors for VWHHO 2XU ÂżUVW JRDO ZDV WR LGHQWLI\ DQG HYDOXDWH QRQ SKRVSKRUXV chemistries for calcium carbonate scale inhibition. Initial screening studies were conducted in heated beakers, and the most promising candidates were evaluated more carefully in a matched pair of fully instrumented pilot cooling towers (Figures 3-5).

Figure 1. TMDL development & application

In cooling towers, algae and cyanobacteria convert inorganic bicarbonate into organic carbon which support the growth of bacteria. The dense algae mats that form on cooling tower decks and exposed areas support higher life forms such as protozoa and amoeba which can harbor and amplify Legionella bacteria. As shown in Figure 2, halogen demand is directly proportional to chlorophyll concenWUDWLRQ $FFRUGLQJ WR /LHELJÂśV /DZ RI WKH 0LQLPXPÂ´ UHVWULFWLQJ phosphorus entering the cooling system is an effective means for reducing algae growth and chlorine demand. Figure 3. Pilot cooling tower schematic

Figure 2. Chlorine demand as a function of chlorophyll concentration

Objective Considering emerging environmental restrictions on phosphorus discharge and the many shortcomings of phosphorus based cooling water treatment technologies, a multi-year research effort was undertaken to develop a versatile and totally phosphorus and zinc free cooling water treatment technology. The requirements for the program were to have no orthophosphate, polyphosphate, or organic phosphonates or phosphinates, yet be cost competitive with traditional phosphorus programs. The program also had to be nontoxic to aquatic life at 10x the nominal use concentration, with an RYHUDOO (QYLURQPHQWDO +HDOWK DQG 6DIHW\ (+ 6 SURÂżOH VLPLODU WR or better than current phosphorus-based programs.

Figure 4. Pilot cooling tower heat exchanger and instrumentation

The pilot cooling towers each have a 15 gallon (56.7 L) sump and evaporate 45 gallons (170 L) daily, with a cold supply water temperature of 100 Â°F (37.8 Â°C) and a hot return temperature of 107.5 Â°F (41.9 Â°C). For the purpose of these experiments, heat exchanger skin temperatures were maintained in the range of 135-142 Â°F (57-61 Â&#x192;& ZLWK D KHDW Ă&#x20AC;X[ RI %WX KU IW : P 6XSHUÂżCTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

FLDO ZDWHU YHORFLW\ LQ WKH DQQXODU Ă&#x20AC;RZ VSDFH ZDV PDLQWDLQHG DW fps (1.2 m/s). The test methodology was to add the scale inhibitor chemistry and cycle up the makeup water (Table 1) gradually over D WKUHH ZHHN SHULRG XQWLO D ÂłFUDVK SRLQWÂ´ ZDV UHDFKHG DV LQGLFDWHG by scale formation on the heat exchanger tubes (Figure 6). Figure 7 indicates that the best of the non-phosphorus scale inhibitors could achieve an LSI of 2.96, corresponding to 5.5 cycles of concentration on the test water.

)LJXUH 3LORW FRROLQJ WRZHUV

)LJXUH $SSHDUDQFH RI WHVW KHDW H[FKDQJHU VXUIDFHV before and after scale development â&#x20AC;&#x153;crash pointâ&#x20AC;?

7DEOH 0DNHXS ZDWHU XVHG IRU QRQ 3 PRGHUDWH DONDOLQLW\ SLORW FRROLQJ WRZHU VWXG\

Corrosion Inhibitor Development Initial screening for non-phosphorus corrosion inhibitors took place using spinner baths and electrochemical tests. The spinner EDWK XQLWV ZHUH RSHUDWHG VR DV WR DFKLHYH D VXSHUÂżFLDO YHORFLW\ RI 1 ft/sec at a controlled temperature. The solutions were aerated to maintain oxygen saturation. Most spinner bath tests were conducted at a bulk water temperature of 50 Â°C (122 Â°F). Corrosion inhibitor performance was also determined through Linear Polarization Resistance (LPR) measurements in cells containing rotating as well as static corrosion coupons. Most of the testing was conducted using the water chemistries shown in Table 2. Additional testing was conducted to evaluate more severe conditions by addition of supplemental chlorides and sulfates, as well as under conditions VLPXODWLQJ ÂżHOG HYDOXDWLRQ VLWHV The testing focused on mild steel corrosion control. Several hundred non-phosphorus candidates were screened over a four-year period. $OWKRXJK PDQ\ FKHPLVWULHV GHPRQVWUDWHG HIÂżFDF\ LQ UHGXFLQJ corrosion, only a few were considered adequate phosphate replace56

Figure 7. Pilot cooling tower study â&#x20AC;&#x201C; Calcium achieved vs. cycles of concentration

ments when dosage, commercial availability, and usage cost were considered. Figures 8 and 9 show the corrosion coupons exposed for 3 days to the untreated baseline water compared to the best performing nonphosphate program. The baseline corrosion rate for this corrosive, ultra-soft water was found to be 60 mpy at 40 Â°C for mild steel. The best-performing non-P program achieved <1 mpy on mild steel and <0.1 mpy on copper. One major drawback to conventional phosphate and zinc programs is that they can be very unforgiving in terms of deposition. In general, the only negative consequence of an overfeed of a non-P inhibitor is an increase in treatment cost. More corrosive conditions can be handled by simply increasing dosage.

CTI Journal, Vol. 35, No. 2

Copper alloy corrosion inhibition One weakness of phosphate is its inability to protect non-ferrous alloys. Aromatic azoles, typically TTA and BZT, must be added to the phosphate programs to protect copper alloys. This chemistry does not offer the same degree of protection for copper alloys as the heritage chromate programs under stressed conditions. Cooling SURJUDPV RSHUDWLQJ LQ WKH S+ ÂłVWDELOL]HG SKRVSKDWHÂ´ FKHPLVWU\ UDQJH IUHTXHQWO\ H[SHULHQFH GLIÂżFXOWLHV REWDLQLQJ DGHTXDWH copper corrosion protection especially during periods of heavy chlorination. The preferred non-P program was evaluated against the baseline stabilized phosphate-azole program in the laboratory using linear polarization resistance measurements. The test water was simulated 8-cycle Sabine River water containing 0.5 ppm free available halogen developed from sodium hypochlorite and sodium bromide. The pH of the water was maintained at 8.0-8.2 with 160 ppm alkalinity and 200 ppm calcium (as CaCO3). As shown in Figure 10, the conventional 3 ppm azole program (red line) performed adequately at <0.1 mpy. However, the non-P program with no azole (blue line) outperformed azole alone. The combination of non-P program in conjunction with 2 ppm azole (green line) demonstrated synergistic behavior in providing the best performance at <0.01 mpy. TDEOH :DWHU FRPSRVLWLRQ XVHG IRU GHYHORSPHQW of soft water program

Figure 8. Baseline mild steel and copper coupon set - corrosive water test

Figure 10. Copper corrosion inhibition comparing azole, the non-P inhibitor, and combination azole with non-P inhibitor

7KH HOHFWURFKHPLFDO WHVWV ZHUH FRQÂżUPHG LQ WKH ODERUDWRU\ XVLQJ GD\ ÂłVSLQQHU EDWKÂ´ VWXGLHV 7DEOH 7KH VWXGLHV LQGLFDWH WKDW the non-P program can produce results equivalent to the baseline phosphate-azole program on both steel and copper at the same 100 SSP SURGXFW GRVDJH +RZHYHU WKH QRQ 3 SURJUDP LV PRUH Ă&#x20AC;H[LEOH The dosage can be dialed up by 30% to produce better corrosion and deposit control protection or reduced by 35% to reduce costs ZLWK D VOLJKW VDFULÂżFH LQ SHUIRUPDQFH

Figure 9. Best performing Non-P steel and copper corrosion coupon set from corrosive water test

$OXPLQXP &RUURVLRQ ,QKLELWLRQ Aluminum corrosion has been of increasing concern due to the more widespread use of aluminum alloys, particularly in closed cooling systems. Unlike steel, which becomes immune to corrosion at high pH, aluminum is an amphoteric metal that corrodes rapidly under alkaline conditions. A 3-day spinner bath study was conducted in aerated 50 Â°C (122 Â°F) tap water to which additional 300 ppm chloride and 100 ppm additional alkalinity were added to provide more challenging condiWLRQV 7KH S+ RI WKH ZDWHU ZDV DOORZHG WR Ă&#x20AC;XFWXDWH LQ WKH CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

range. Corrosion coupon appearance and aluminum concentration in the test solution were used as an indication of corrosion, since aluminum coupons actually gain weight as they corrode due to precipitation. The non-P formulated product was evaluated at 100, 200, and 300 ppm product. Results are shown in Table 4. Corrosion on aluminum occurs when the protective aluminum oxide layer is damaged either mechanically or chemically. Pits on the baseline coupons were surrounded by white precipitate, suggesting that anodic sites developed in the absence of effective treatment. The non-P treatment program completely eliminated anodic pitting at the 300 ppm product concentration.

7DEOH ,QLWLDO ZDWHU DQDO\VLV IRU GD\ aluminum spinner bath study

Corrosion Control Mechanism Electrochemistry studies were used to elucidate the corrosion inhibition mechanism of the new treatment chemistry on steel. As shown in Figure 11, the corrosion inhibitor package inhibits both the anodic and cathodic corrosion processes, showing the tendency to form a SDUWLFXODUO\ VWURQJ SDVVLYH 多OP RQ WKH DQRGLF UHJLRQ

Table 3. Results of baseline phosphate vs. non-P programs in a 3-day spinner study

Figure 11. Electrochemcial study of non-P inhibtor on steel

Field applications of non-P Programs 1. Low hardness, Low alkalinity Corrosive Water Application The best performing non-P program in the laboratory was formuODWHG DV D FRPPHUFLDO SURGXFW DQG WDNHQ WR D 多HOG HYDOXDWLRQ LQ D corrosive water application where phosphate discharge was becoming a concern. The small 2-cell Evapco cooling tower servicing a HVAC system was using a conventional phosphate-based program and obtaining marginal results of 3.4 - 4.6 mpy on mild steel. ProFHVV FRQGLWLRQV PDGH LW GLI多FXOW WR REWDLQ WKH FRQVLVWHQW FKHPLVWU\ required by phosphate-based programs, and the small size of the V\VWHP PDGH LW GLI多FXOW WR MXVWLI\ DXWRPDWLQJ WKH FKHPLFDO GRVLQJ systems. The non-P program improved performance to 1.4 mpy on mild steel and <0.01 mpy on copper. Thermal performance of Table 4 . Effectiveness of non-P chemistry on aluminum corrosion

CTI Journal, Vol. 35, No. 2

Table Top Exhibits 7XHVGD\ )HEUXDU\ Â&#x2021; S S Sheraton New Orleans, New Orleans, Louisiana

'RQÂśW IRUJHW WR UHVHUYH \RXU VSDFH $ WRWDO RI H[KLELW VSDFHV DYDLODEOH DW VSDFH ZLWK D QXPEHU RI WDEOHV DOUHDG\ reserved (sold spaces indicated by red boxes) IRU PRUH LQIRUPDWLRQ FRQWDFW 9LUJLQLD 0DQVHU DW or vmanser@cti.org Exhibitors to date: EvapTech ChemTreat, Inc Design Controls C.E. Shepherd FasTec Structural Group Resolite GEA 2H Water Composite Cooling Solutions French Creek Software Baltimore Aircoil

CTI Journal, Vol. 35, No. 2

IMI Sensors Sonitec-Vortisand Hewitech GmbH Midwest Cooling Tower McHale & Associates Proco SPX Cooling Technologies Dynamic Fabricators Glocon Aggreko Amarillo Gear Bedford Reinforced Plastics

Hudson Products &RÂżPFR Rain For Rent G&G Marine AMSA, Inc. Denso North America Clean Air Engineering Tower Tech CoolWater Technologies Gaiennie Lumber Strongwell Brentwood Industries

critical heat exchangers has shown no decline in performance since transitioning to the non-P treatment program. Figures 12 and 13 show the copper and steel coupons after a 64-day exposure.

VKRZLQJ UDWHV RI PS\ IRU WKH ÂżUVW GD\V PS\ IRU WKH second 32 days, 0.80 mpy for the third 32 days, and 0.32 mpy for WKH ÂżUVW GD\V &ULWLFDO KHDW H[FKDQJHU DSSURDFK WHPSHUDWXUHV KDYH UHPDLQHG Ă&#x20AC;DW )LJXUH VKRZV WKH DSSHDUDQFH RI WKH LQLWLDO steel coupon after 35 days before and after cleaning.

Figure 12. Field trial coupons before cleaning

Table 6. High hardness and sulfate water Figure 13. Field trial coupons after cleaning

High Hardness, High Sulfate Corrosive Water Application A Midwest cogeneration plant faced stringent phosphate discharge UHJXODWLRQV 7KH XQFODULÂżHG PDNHXS ZDWHU ZDV KLJK LQ FDOFLXP and alkalinity, requiring sulfuric acid for pH control. The resulting cooling water was relatively corrosive due to high sulfates from the use of acid. The circulating water is shown in Table 6. Steel corrosion rates on the baseline low-phosphorus program were averaging about 10 mpy (Figure 14). Upon changing to the non-P chemistry, corrosion rates have been reduced to a 2 mpy average on steel (Figure 15) and 0.1 - 0.2 mpy on copper.

)LJXUH ,QLWLDO VWHHO FRXSRQ GD\V before and after cleaning, 1.07 mpy

Figure 14. Baseline Low-P program

7DEOH $YHUDJH FRROLQJ ZDWHU FKHPLVWU\

4. High iron in well water application )LJXUH 1RQ 3 SURJUDP LQLWLDO FRXSRQ Well water iron poses a special challenge for phosphate-based 3. Gulf Coast Chemical Plant treatment programs. The reactive iron precipitates the phosphate The formulated product was evaluated at a Gulf Coast chemical corrosion inhibitor, rendering the phosphate ineffective and creSODQW FRROLQJ WRZHU RSHUDWLQJ DW F\FOHV RQ FODULÂżHG 6DELQH 5LYHU ating a sticky iron phosphate precipitate that creates additional water. The water is relatively corrosive and several heat exchang- polymer demand and tends to precipitate on heat transfer surfaces. ers with high temperatures have been prone to deposition over the Non-phosphorus treatment programs are particularly suited to such years. Although the corrosion results have been excellent in the applications because the corrosion inhibitor does not react with the past, the plant wanted to use a more forgiving, non-fouling program. iron and the dispersant is only required to disperse the iron itself Corrosion coupon results have been excellent, with steel coupons 62

CTI Journal, Vol. 35, No. 2

rather than precipitated iron phosphate. A Gulf Coast air separation plant with 2-5 ppm iron in its well water was experiencing heat exchanger fouling problems on a phosphate based treatment program. The problems were severe enough to require shutdowns to clean the exchangers. Figure 17 shows the last set of coupons removed from the phosphate program with heavy deposition and obvious corrosion.

$SSURDFK WHPSHUDWXUHV KDYH LPSURYHG GXULQJ WKH ÂżUVW IRXU PRQWKV on the non-phosphorus program (Figure 20) along with an increase in tower water turbidity, indicating that softer deposits are slowly being removed. 5. Steam Jacketed Vessel Application One particularly challenging application for phosphate based cooling water programs is the treatment of jacketed reactor vessels that are alternately exposed to steam for heating followed by cooling tower water for the process cooling cycle. The jacket is alternately exposed to high temperature steam followed by oxygenated cooling ZDWHU 7KH SURWHFWLYH ÂżOP DSSOLHG GXULQJ WKH FRROLQJ F\FOH PXVW somehow persist through the high temperature, low hardness steam heating cycle. This was readily achievable during the chromate and zinc era, but not generally possible with phosphate based programs. 7KH QRQ 3 FKHPLVWU\ SURGXFHV D PXFK PRUH SHUVLVWHQW ÂżOP WKDQ phosphate programs, making it an excellent application for steam jacketed vessels.

Figure 17. Phosphate program, steel, admiralty, and copper coupons with high well-water iron

The treatment program was converted to the non-phosphorus program with the addition of a non-P supplemental dispersant for iron. Results on both corrosion and fouling have improved substantially. )LJXUH VKRZV WKH ÂżUVW FRXSRQ VHW UHPRYHG DIWHU GD\V

Figure 19. Non-P program 90-10 Cu:Ni coupons, 73-day exposure in high iron water before and after cleaning

Table 8. Cooling water chemistry

)LJXUH 1RQ 3 SURJUDP ÂżUVW FRXSRQ VHW UHPRYHG DW GD\V Steel 1.06 mpy, admiralty 0.68 mpy, and copper 0.31 mpy

The automation system had not been installed yet, and there were several periods of high chlorine residual that adversely affected copper alloy corrosion. The second set of coupons exposed for 73 days fared better with corrosion rates of 0.11 mpy on 90-10 coppernickel (Figure 19) and 1.55 mpy on mild steel.

A Gulf Coast chemical plant was experiencing elevated steel corrosion rates in their jacket water cooling system, typical for a phosphate program. The corrosion rate was 6.8 mpy on steel coupons, resulting in nearly 4 ppm iron in the cooling tower water. The phosphate based program was overlaid with the non-P corrosion inhibitor program. Iron levels in the tower dropped to 0.5 ppm as VKRZQ LQ )LJXUH DQG WKH FRUURVLRQ UDWH RQ WKH ÂżUVW GD\ FRXSRQ was reduced to 1.34 mpy.

CTI Journal, Vol. 35, No. 2

)LJXUH $SSURDFK WHPSHUDWXUH WUHQG RQ WKH QRQ 3 SURJUDP system transitioning to non-P program overlay

)LJXUH &RROLQJ WRZHU LURQ OHYHO IRU MDFNHWHG YHVVHO FRROLQJ

7DEOH &RROLQJ 7RZHU &KHPLVWU\ IRU -DFNHWHG 9HVVHO

CTI Journal, Vol. 35, No. 2

Aquatic Effects and EH&S Since the initial goal of the program was to develop an environmentally sound alternative to phosphate treatment programs, one of the major criteria was to have minimal aquatic effects, including mortality to EPA marker organisms, minimal human exposure hazards, no zinc, and no phosphorous in any form. A range of formulated products have been developed around the basic non-P corrosion inhibitor technology. Most are formulated at a mildly acidic pH. This is considerably less hazardous than most of the products it replaces, which must be formulated under strongly caustic or strongly acidic pH. The cautionary wording is considerably less onerous, and the HMIS rating is typically 1-0-0-X. The basic formulated product is applied at a nominal dosage of 100 ppm. The LD50 acute effect concentration is approximately 3,000 mg/L for both Ceriodaphnia and fathead minnow, and the 7-day chronic no-effect level for fathead minnow is 3,500 mg/L. Another version of the formulated product is also totally nitrogen free, including no azole and no acrylamide or AMPS containing polymers. The LD50â&#x20AC;&#x2122;s of that non-N and non-P product are 3,700 mg/L for Ceriodaphnia and 6,300 mg/L for fathead minQRZ 7KH VLJQLÂżFDQW VDIHW\ PDUJLQ EHWZHHQ DSSOLFDWLRQ GRVDJH and aquatic effect concentration, the total absence of phosphorus and even nitrogen, and the mildly acid formulation should enable

CTI Journal, Vol. 35, No. 2

the products to be applied safely and discharged under current US regulations.

Conclusions Practical non-phosphorus cooling water treatment programs have been developed to comply with emerging regulatory restrictions. 1RQ SKRVSKRUXV FKHPLVWU\ RIIHUV VHYHUDO NH\ EHQHÂżWV LQ DGGLWLRQ to environmental compliance. Most importantly, these non-P SURJUDPV Â&#x2021; Â&#x2021;

Â&#x2021; Â&#x2021; Â&#x2021; Â&#x2021; Â&#x2021; Â&#x2021;

Are non-fouling with a broad control band Do not contribute to algae growth either in the environment or in the cooling tower, thus resulting in lower chlorine demand Are effective in zero hardness or high hardness waters Effective on steel, copper, and aluminum Are not affected by well-water iron or aluminum carryover )RUP D PRUH SHUVLVWHQW ÂżOP WUHDWLQJ WKH VXUIDFHV UDWKHU than the bulk water +DYH PLQLPDO DTXDWLF HIIHFWV DQG D IDYRUDEOH (+ 6 SURÂżOH Provide superior performance to phosphate based - programs.

1RLVH &RQWURO 2I :DWHU &RROLQJ 7RZHUV ,Q 5RPH V +RVSLWDO $UHD Augusto Papa, Phd Italian Workers Compensation Authority

2.2 Replacement of cooling towers 7KH SURMHFW LQYROYHV WKH UHSODFHPHQW RI WKH ÂżYH existing towers with four new towers, which should allow 8 dBA noise reduction. 7KH QHZ FRQÂżJXUDWLRQ LQFOXGHV Â&#x2021; Three cooling towers (TR1-TR2-TR3 Figure 1) engines 15 kW, with modules equipped with three fans; Â&#x2021; A cooling tower operating on two groups dedicated to the refrigerator after cooling batter-ies, motors 5.5 kW and module equipped with two fans.

1. Introduction A new cooling power plant subservient to the "Accident & Emergency" building with replace-ment of the existing cooling towers to be built at the Catholic University General hospital "Agostino Gemelli" in Rome, in largo Agostino Gemelli, n. 8. The client wants to evaluate compliance with WKH VSHFLÂżFDWLRQV DQG UHJXODWLRQV RI WKH QHZ DLU conditioning systems that will be installed, from the point of view of noise.

2.3 Local generator enlargement The project also includes expansion of the existing space and the installation of a new electric generator.

$XJXVWR 3DSD

The contract includes installation of new machines, resulting in a noise reduction of at least 8 dBA compared to the noise of the existing plants.

Various sound level measurement has been carried out in the hospital area during the night to characterize the existing refrigeration cooling tower units and to detect the residual noise of the area. 7KH ÂżUVW GDWD UHFRUGHG LV FRQVLGHUHG D UHIHUHQFH IRU FRPSDULVRQ with the results of the estimates, while the residual noise was used in order to build the prediction emission scenario. The noise model prediction is created using the software CADNA and appropriate algorithms.

3 Sources noise emission The machines that will be installed are characterized, from the noise point of view, to the acoustic emission data provided by the manufacturer (table 1). This data shows the noise measured at 1.5 meters and at a height of 4 metres above ground lev-el. The data in Table 1 shows the number of machines installed, brand name, series, and acronyms, in reference to Figure 1.

The new source emission data has been provided by the water cooling tower manufacturer.

4 Characterization measurements of the current sources and residual noise

The estimation of environmental noise expected as a result of the installation of four new towers and new fridge plants, resulting from the noise scenario, was compared with the sound levels currently present, also in order to verify compliance with the noise limits established by applicable Laws.

The sources analyzed are of the current cooling towers TE1, TE2, TE3, TE4, TE5 subservient to the Accident & Emergency building of The General Hospital A. Gemelli.

:RUN DFWLYLW\ GHVFULSWLRQ 7KH ZRUN LQFOXGHV WKUHH SKDVHV &RQVWUXFWLRQ RI D QHZ FRROLQJ power plan, 2) Replacement of cooling towers; 3) local generator enlargement

2.1 Construction of a new cooling power plant The new plant includes the installation of three new absorption chillers. The installation of pump assembly for the chilled water circuit and the circuit water tower have been planned as service of new absorption units. Hot water pumps are also provided. Connections to existing pipelines will be carried out by the construction of a tunnel installation inspection that will be installed in the basement of the Accidents & Emergency building.

'XULQJ WKH QRLVH VXUYH\V QR SXPSV ODUJH WRZHU IDQV 7( TE2 and TE3) and 4 small tower fans (TE4 and TE5) were put in operation. The evaporation tower noise is characterized by the contribution of WZR W\SHV RI VRXQG VRXUFHV ÂżJXUH 1) Fan noise; 2) Water Noise. 7KH ÂżUVW FRQWULEXWLRQ IDQ QRLVH LV WKH VRXQG RI ORZ PLG IUHTXHQcies and longer frequencies passing through walls and obstacles, that LW LV GLIÂżFXOW WR PLWLJDWH DQG SURSDJDWHV IURP WKH WRS The second contribution "water noise" is a noise at height frequencies, depending on water loading (Q/A), that naturally attenuates with distance, that is masked easily with simple barriers, and propagates from below. Regarding the above situation, in order to better the sound source characteristics in the 3 survey points, two measurements of LeAq are carried out contemporaneously, both at a height of 1.5 meters to

CTI Journal, Vol. 35, No. 2

better emphasize the contribution of the "water noise", at a height of 4 meters for the contribution of the "fan noise". The measurement taken at 4 meters was carried out in order to eliminate the source of wind un-certainty, with the microphone outside the discharge zone at high air velocity, also in reference to the VSHFLÂżF VWDQGDUG $7& &RROLQJ 7HFKQRORJ\ ,QVWLWXWH 6WDQGDUG

4.1 Measuring points The choice of measuring points was established in reference positions that showed the best acces-sibility condition during the inspection, also considering the future space destination project , neces-sary for post work measurements and the receptor location. Therefore, 3 points were chosen around the evaporation towers (Figure 9-10). Â&#x2021; 3RLQW 1H[W WR VWDLUV ORFDWLRQ QRUWKHDVW DERXW P from the center of TE2 Â&#x2021; 3RLQW 1H[W WR ORFDO 4( 6RXWKHDVW ORFDWLRQ DERXW m from the center TE2; Â&#x2021; 3RLQW 1H[W WR SDWK +HOLSRUW ORFDWLRQ QRUWK ZHVW DERXW 5 m from the center TE2. :RUNLQJ FRQGLWLRQV GXULQJ WKH PHDVXUHPHQWV The sound level measurements took place during the night (from SP WR DP 7KH PHDVXUHPHQWV ZHUH PDGH DW WZR KHLJKWV to better characterize the source. 'XULQJ WKH PHDVXUHPHQW WKHUH ZHUH Q SXPSV Q IDQV ODUJH towers and n. 4 small towers fans in operation. From the data of the measurements performed, as expected, there was a higher sound level of the measurements performed at 4 meters, compared to 1.5 meters (Figures 11-13), the latter are character-ized by a greater contribution of low frequencies (Figures 14). The sound measurements with current cooling towers were carried out in order to compare the sound levels obtained, with those expected as a result of the replacement with four new Super silent towers .

$FRXVWLF 0XQLFLSDO FODVVLÂżFDWLRQ The legislation establishing the criterion of zoning, each municipality must divide its territory into six classes, each subject to a different noise limit. The hospital area acoustic class, is class I ^ acoustic zoning of the &LW\ RI 5RPH VSHFLDO SURWHFW HG DUHDV This class includes the areas where tranquillity is a basic element IRU KRVSLWDOV DUHDV VFKRROV UH OD[ DQG OHLVXUH DUHDV UXUDO UHVLdential areas, areas of particular interest in urban planning, public parks, etc..

rays traced during their path undergo an energy attenuation content GXH WR JHRPHWULF GLYHUJHQFH EHFDXVH RI WKH UHĂ&#x20AC;HFWLRQ HIIHFWV DWtenuation due to dissipation in the middle, effect of the soil and of any obstacles, weather effects and effects related to the diffraction phenomena . The path of each individual beam shows how much the incident wave is attenuated from a given source of noise. For the study of the noise source emission and noise propagation, the software has the main algo-rithms validated on a national and international level. Among these, those recommended by the Euro-pean Commission are included , in particular the methods of calculating 103% 5RXWHV *XLGH GX EUXLW IRU YHKLFXODU WUDIÂżF WKH QRUP "ISO 9613-2" for the calculation of the noise from industrial sources, DQG WKH PHWKRG RI FDOFXODWLRQ 'XWFK 505 IRU UDLO WUDIÂżF QRLVH 2SHUDWLQJ FRQGLWLRQV VSHFLÂżHG LQ WKH PRGHO )LJXUH Â&#x2021;

:DWHU WRZHU SXPSV DV D IXQFWLRQ RI IRU HDFK WRZHU E1 to E6;

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Chilled water pumps in operation depending on n. 3 to 6 IRU HDFK UHIULJHUDWLRQ XQLW ( WR (

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6.1 Estimated noise and measured values Comparison The results obtained by calculation software CADNA 4.0 for enYLURQPHQWDO QRLVH /$

UHSUH VHQWHG LQ WKH VFHQDULR ÂżJ DUH compared with environmental noise measurements (LA) carried out at the same reference points, on the 18th day / April 19, 2013 on the existing towers (table 2).

7 Noise Reduction According to the results of table 2, to ensure the noise reduction of 8 dBA it is necessary to take some action, such as cover panels of refrigerator groups and silencer installations.

7.1 Refrigerator group cover panels Internal sound absorbing panelling will be installed to the chillers as shown in table 3. PGB PWD-F sound-absorbing and soundinsulating mineral wool panels. The panels are made of two layers of steel enclosed between a PLQHUDO ZRRO LQVXODWLRQ ZLWK VWDJ JHUHG MRLQWV RULHQWHG ÂżEUHV DQG high density. 7KH SDQHOV IRU WKH URRI DUH RI FXUYHG W\SH LQVXODWLRQ &7' URRÂżQJ system insulated panels "Mar-cegaglia" a single span, double-hinged arch (Figure 16).

7.2 Silencer Installation The noise limits are very low especially at night-time (10.00 pm In order to reduce the tower noises optional abatement systems must WR DP ZKHQ WKH LQSXW YDOXH PXVW QRW H[FHHG G%$ DW WKH be installed, circular absorbing silencers with nose cone, installable receptor. in expulsion to the fan. The circular silencers, SLN used in expulsion, are mounted above For the acoustic modelling a calculation software based on the the diffuser using threaded inserts on the heads of the same mufprinciple of ray tracing has been used. A ray tracing algorithm dis- Ă&#x20AC;HUV 7KH\ DUH FKDUDFWHUL]HG E\ RSWLPXP QRLVH DWWHQXDWLRQ ORZ cretization was employed to calculate energy emitted by a source SUHVVXUH GURS DQG KLJK VWUHQJWK FRQVWUXFWLRQ ÂżJXUH 7KHVH DQG LW LV XVHG WR FDOFXODWH WKH VRXQG ÂżHOG DW D SRLQW DV D VXSHUSRVLWLRQ W\SHV RI VLOHQFHUV DUH DYDLODEOH LQ WZR VHULHV 6/1 ZLWKRXW QRVH contribution of the various rays that pass through the same point. The cone (N), and with SLN nose cone (O), with lengths equal to one or two times the diameter.

6 Provisional scenarios

CTI Journal, Vol. 35, No. 2

In this case study silencer nose cone models are used, 1400 mm nominal diameter, because they have a stronger ability of noise attenuation compared to models without a nose cone (table 4). The standard construction is galvanized steel and the special soundDEVRUELQJ PDWHULDO LV PLQHUDO ÂżEUH SUR WHFWHG E\ SHUIRUDWHG VKHHW metal.

9 References

3DSD $ $GGRQL]LR 3 $FRXVWLF UHTXDOLÂżFDWLRQ IRU WHUULWRrial structures by inail following partial change of purpose for residential use, AIA-DAGA 2013 Conference, Merano (2013);

Papa A, Mariconte R., Metodologie di valutazione dellâ&#x20AC;&#x2122;immissione di rumore a bassa frequenza, 39Â° Convegno Nazionale dellâ&#x20AC;&#x2122; Associazione Italiana di Acustica, Roma (2012);

Papa A, Mariconte R., Le valutazioni di clima e di impatto DFXVWLFR VWUXPHQWL H SUREOHPDWLFKH FRQQHVVH Â&#x192; &RQgresso Nazionale CIRIAF, Perugia (2010);

Papa A, Mariconte R., Impiego dei modelli previsionali per la valutazione del clima ed dellâ&#x20AC;&#x2122;impatto acustico, 1Â° Convegno Nazionale sulla Governance del Rumore Ambientale; Ischia (2009);

8 Conclusions This paper concerns the forecast evaluation of noise impact in order to establish compliance with terms of contract and the currently applicable laws on noise, about new air conditioning systems that will be installed following the construction of a modern refrigeration system subservient to the Acci-dent & Emergency building at the General Hospital A. Gemelli in Rome. We have described the different actions of the project showing the lay-out of the machines (Fig-ure 1), and their emission sound levels at a distance of 1.5 m and 4 m above ground level (table 1). To characterize the existing cooling towers of the refrigeration unit and to detect the residual noise of the area, various sound level measurements were carried out during the night.

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The measurements of the residual noise and emission data of the new VRXUFHV FHUWLÂżHG E\ WKH PDQXIDFWXUHU DUH FRPELQHG WR EXLOG WKH emission prediction model, using the software CADNA DataKustik vers. 4.0, and appropriate algorithms. The acoustic modeling of the area, has produced a scenario for the ZHHNO\ QLJKW GD\ SHULRG ÂżJ ZKHUH VRXQG LVROHYHO VXUIDFHV (equal loudness) with colors representing the various noise levels are shown as indicated in the key. The model shows numeric text boxes of the noise levels expected of the control points placed exactly in the same positions of the measurement points used on the current machines.

Figure 1: Project Lay out with reference to installed machines

The estimated values of environmental noise, obtained from this prognosis study, concerning the installation of four new towers and new fridge plants are compared with the actual sound levels meas-ured. This comparison shows a reduction in the three control points ranging from 5.1 to 6.4 dBA with an average of about 5.8 dBA, therefore less than 8 dBA guaranteed by contract. Therefore, to ensure the right noise reduction some mitigation is UHTXLUHG 1.

Coverage of the refrigeration unit, panels of insulating materials ;

Install additional abatement systems for cooling towers, such as sound-absorbing circular silencers with nose cone.

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These actions will ensure a certain reduction of more than 3 remaining dB to comply with the agreements (estimated at least 5-6 dB). Unfortunately up to now the silencers have not yet been in-stalled, and so it is not yet possible to perform measurements of the actual noise abatement. But thanks to our provisional acoustic study it could help the manufacturer indicate the necessary action to ensure compliance in the contract of the client.

Figure 3: Location of the new refrigerating plant

CTI Journal, Vol. 35, No. 2

Figure 9: Location of measuring points around the current cooling towers Figure 4: New cooling towers

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Figure 10: P1 and P2 Measuring points

Figure 6: Perspective 2 - existing cooling towers

Figure 11: P1 measuring point -environmental noise level history

Figure 7: Sound cooling tower contributions Figure 12: P2 measuring point -environmental noise level history

Figure 8: Microphone position for measurements at 4 m

Figure 13: P3 measuring point environmental noise level history

CTI Journal, Vol. 35, No. 2

Figure 14: P3 measuring point - environmental noise level Spectrum Comparison 7DEOH $FRXVWLF HPLVVLRQV FHUWL多HG E\ WKH manufacturers of new sound sources

7DEOH 3RLQWV RI UHIHUHQFH PHDVXUH expected values Differential level )LJXUH 3RVW ZRUN QLJKW HQYLURQPHQWDO QRLVH Scenario with equal loudness curves and 0DUNHU VRXQG OHYHOV LQ WKH FRQWURO SRLQWV

7DEOH $FRXVWLF FKDUDFWHULVWLFV FRROLQJ XQLW FRYHUDJH DUHD SDQHOLQJ 3*% 3:' ) )LJXUH &RYHU SDQHOV &7' VFKHPDWLF UHSUHVHQWDWLRQ

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Figure 17: Silencer scheme

Figure 18: Silencer Photo

CTI Journal, Vol. 35, No. 2

&RROLQJ 7RZHUV &HUWLÂżHG E\ &7, 8QGHU 67' 7KH KLVWRU\ RI WKH &7, 67' 7KHUPDO 3HUIRUPDQFH &HUWLÂżFDWLRQ Program since 1983 is shown in the following graphs. A total of 36 cooling tower manufacturers are currently active in the program. In addition, 8 of the manufacturers also market products as private brands through other companies. While in competition with each other, these PDQXIDFWXUHUV EHQHÂżW IURP NQRZLQJ that they each achieve their published performance capability and distinguish themselves by providing the Owner/ Operatorâ&#x20AC;&#x2122;s required thermal performance. The participating manufacturers currently have 89 product lines plus 13 product lines marketed as private brands which result in more than 18,029 cooling tower models with CTI STD 7KHUPDO 3HUIRUPDQFH &HUWLÂżFDWLRQ IRU FRROLQJ WRZHU 2ZQHU &7, &HUWLÂżFDWLRQ XQGHU 67' LV OLPLWHG WR WKHUPDO RSHUDWLQJ Operatorâ&#x20AC;&#x2122;s to select from. The following table lists the currently conditions with entering wet bulb temperatures between 12.8Â°C active cooling tower manufacturers, their products with CTI STDDQG Â&#x192;& Â&#x192;) WR Â&#x192;) D PD[LPXP SURFHVV Ă&#x20AC;XLG WHPSHUDWXUH 7KHUPDO 3HUIRUPDQFH &HUWLÂżFDWLRQ DQG D EULHI GHVFULSWLRQ RI of 51.7Â°C (125Â°F), a cooling range of 2.2Â°C (4Â°F) or greater, and a the product lines. cooling approach of 2.8Â°C (5Â°F) or greater. The manufacturer may Those Manufacturers who have not yet chosen to certify their prodset more restrictive limits if desired or publish less restrictive limits uct lines are invited to do so at the earliest opportunity. You can contact Virginia A. Manser, Cooling Technology Institute, PO Box LI WKH &7, OLPLWV DUH FOHDUO\ GHÂżQHG DQG QRWHG LQ WKH SXEOLFDWLRQ 73383, Houston, TX 77273 for further information. As stated in its opening paragraph, CTI Standard 201... "sets forth a program whereby the Cooling Technology Institute will certify that all models of a line of water cooling towers offered for sale E\ D VSHFLÂżF 0DQXIDFWXUHU ZLOO SHUform thermally in accordance with the Manufacturer's published ratings..." %\ WKH SXUFKDVH RI D FHUWLÂżHG PRGHO the Owner/Operator has assurance that the tower will perform as specified, provided that its circulating water is within acceptable limits and that its air supply is ample and unobstructed. Either that model, or one of its close design family members, will have been thoroughly tested by the single CTIOLFHQVHG WHVWLQJ DJHQF\ IRU &HUWLÂżFDWLRQ and found to perform as claimed by the Manufacturer.

CTI Journal, Vol. 35, No. 2

NUMBER OF CTI CERTIFIED TOWER MODELS 18000

Through 6/30/2014

17000

Private Brands

16000

Manufacturer Brands

15000 14000 13000 12000 11000 10000 9000 8000 7000 6000 5000 4000 3000 2000

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987

1986

1985

1984

1983

1000

YEAR CTI Journal, Vol. 35, No. 2

CTI Journal, Vol. 35, No. 2

,QGH[ RI $GYHUWLVHUV Advance GRP Cooling Towers Pvt Ltd (India) ....5 Aggreko Cooling Tower Services ................. 44, 45 AHR Expo..............................................................21 Amarillo Gear Company....................................IBC American Cooling Tower, Inc...............................39 AMSA, Inc. ............................................................31 BailSco Blades & Castings, Inc............................20 Baldor Electric Company......................................35 Bedford Reinforced Plastics .................................13 Brentwood Industries ..............................................7 ChemTreat, Inc. .....................................................53 Composite Cooling Solutions, LP ........................25 Cooling Tower Resources .....................................43 &7, &HUWL多HG 7RZHUV.............................................80 CTI License Testing Agencies ..............................78 CTI Owner/Operators............................................75 CTI STD-202 .........................................................79 CTI Table Top Exhibits .........................................61 CTI ToolKit ............................................................86 Denso......................................................................57 Dynamic Fabricators .............................................11 Fuel Ethanol ...........................................................59 Electric Power Conference/Exhibition.................73 Gaiennie Lumber Company ...................................2 Glocon ......................................................................3 Hewitech ................................................................67 Howden Cooling Fans...........................................47 Hudson Products Corporation ..............................27 IMI Sensors ............................................................15 Industrial Cooling Towers .............................. IFC, 6 International Chimney...........................................71 Kemrock.................................................................49 Kipcon ....................................................................55 KIMCO ..................................................................17 Midwest Cooling Towers ......................................51 Moore Fans ............................................................23 North Street Cooling Towers ................................65 Power Gen..............................................................19 Qualichem ..............................................................37 Research Cottrell Cooling .......................................4 Rexnord Industries...................................................9 C.E. Shepherd Company, LP ................................63 Simpson Strong-Tie...............................................33 Spraying Services, Inc. ..........................................41 SPX Cooling Technologies ..............................OBC Strongwell ..............................................................29 Tower Performance, Inc. ................................ 66, 88 Turbo Machinery ...................................................77 Walchem.................................................................69

CTI Journal, Vol. 35, No. 2