February 2016 by Energy-Tech Magazine

Outage planning 20 • Lower weld rejection rates 12 • ASME: Bolting qualifications 24

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FEBRUARY 2016

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Over fivesessions, days, experience conferences, two forums, keynote,opportunities. plenary, technical, panel & poster technicalfour workshops, plus multiple networking & poster sessions, technical workshops, plus world-class multiple networking opportunities. Our program was developed in tandem with energy leaders on our Executive Our program was developed in tandem with world-class energy leaders on our Executive Advisory Committee Advisory Committee Unlike other conferences, ASME 2016 Power & Energy concentrates on a broad range of Unlike other conferences, 2016 Powerincluding & Energypower, concentrates a broad range topics for “Engineering theASME Energy Portfolio” nuclear,on renewables and of topics “Engineering the Energy Portfolio” including power, nuclear, renewables and diversefor portfolios. diverse portfolios. From plant operations & maintenance, smart grids, solar heating & cooling, high & low From plant operations maintenance, smartmodular grids, solar heating & SO cooling, high & low— you will temperature fuel cells, & advanced and small reactors AND MUCH MORE temperature cells, at advanced small modular reactors AND SO MUCH MORE — you will learn from thefuel experts Power &and Energy! learn from the expertsatatthe Power Energy! Interact with vendors expo&and view the latest equipment and technology on the market. Interact with vendors at the expo and view the latest equipment and technology on the market.

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FEATURES

By Behrang Pakzadeh, Ph.D., P.E., Brad Buecker, Mitchell Krasnopoler, P.E., Kiewit Engineering & Design Co.

Editorial Board (editorial@WoodwardBizMedia.com) Bill Moore – Director, Technical Service, National Electric Coil Ram Madugula – Executive Vice President, Power Engineers Collaborative, LLC Kuda Mutama – Engineering Manager, TS Power Plant Tina Toburen – T2ES Inc.

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Maintenance Matters

Managing generation assets under changing mission profiles By Ray Chambers, Revis James and Norris Hirota, Electric Power Research Institute Turbine Tech

Turbine Tech

Outage planning – Best practices and steps you can’t afford to skip! By Steve Reid, PE, and Tom Reid, TG Advisers Inc.

Editorial views expressed within do not necessarily reflect those of Energy-Tech magazine or WoodwardBizMedia. Advertising Sales Executives Joan Gross – jgross@WoodwardBizMedia.com

A people-centered approach to lowering weld rejection rates By John E. Miller, Day & Zimmermann

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Comparing evaporation and bioreactors for FGD wastewater treatment

Machine Doctor

Catastrophic centrifugal compressor failure during shutdown By Patrick J. Smith, Energy-Tech contributor

ASME FEATURE

The impact of qualified bolting specialists on the safe, reliable assembly and operation of bolted flanged connections By A. Fitzgerald (Jerry) Waterland II, VSP Technologies; David Lay, Hytorc; and Michael Dodge, ASME

INDUSTRY NOTES

4 34

Editor’s Note and Calendar Advertiser’s Index

ON THE WEB There’s still time to register for Energy-Tech University’s Feb. 16-18, Secrets to Executing a Successful Turbine-Generator Outage, with Steve Reid, PE, and Tom Reid, of TG Advisers. Visit www.energy-tech.com/ outage to learn more and register.

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EDITOR’S NOTE

Changes in 2016 Energy-Tech has more in store for the year ahead

Welcome to Energy-Tech’s first quarterly issue of 2016! I hope that you’re enjoying our new editorial format and are receiving the weekly email newsletters that will keep you informed between our print issues through the rest of the year in May, August and November. This year is bringing lots of changes to EnergyTech, not only with how we publish the magazine, but also what we plan to offer. We’ve been ramping up our webinar courses for the past few years, but this year we plan to have one every month, on a wide variety of topics – from heat exchangers to turbines to water use. As you plan your training schedule this year, consider an EnergyTech webinar. They’re affordable, easy to access and as informative as sitting in a classroom. And you can still make it home for dinner on time.You can find out more at www.energy-tech.com, I hope you’re able to join us. One final change is that this will be my last issue as managing editor for the magazine. I’ve accepted a new job with an industry-leading textbook publishing company, which I’ll be a few weeks into as you read this. While I’m very excited about the new professional opportunity, I’ll miss working on this magazine that I’ve put so much energy and effort into during the last eight years. When I started working on Energy-Tech, it was a huge learning curve for me, but I’ve enjoyed learning more about the power generation industry, meeting the experts who would become our contributors and talking to readers at the ASME Power & Energy Conference and Electric Power. It was always really interesting – even if my friends’ eyes glazed over when I would try to tell them about it. Thank you for reading Energy-Tech during the past eight years. Thank you for attending the webinars I worked on, for stopping by the conference booth to introduce yourselves and for letting me know when you really agreed with an article – and when you really didn’t. I hope you will continue to stay engaged with Energy-Tech and will be as welcoming to the next editor as you were to me. If you have any questions, please contact the magazine’s General Manager Randy Rodgers by emailing randy.rodgers@woodwardbizmedia.com. As always, thanks for reading. It’s been a lot of fun.

CALENDAR Feb. 16-18, 2016 ETU Online Training: The Secrets to Executing a Successful Turbine-Generator Outage www.energy-tech.com/outage March 9-10, 2016 ETU Online Training: Condenser Solutions – Improve Performance, Enhance Efficiency www.energy-tech.com/condenseressentials April 18-21, 2016 Electric Power Conference & Exhibition New Orleans, La. www.electricpowerexpo.com June 13-14, 2016 Fugitive Emissions Summit Americas Houston, Texas www.fugitive-emissions-summit.com June 26-30, 2016 ASME 2016 Power & Energy Conference & Exhibition Charlotte, NC www.asme.org/events/power-energy Dec. 13-15, 2016 Power-Gen International Orlando, Fla. www.power-gen.com Submit your events by emailing editorial@woodwardbizmedia.com.

Andrea Hauser

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February 2016

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FEATURES

Comparing evaporation and bioreactors for FGD wastewater treatment By Behrang Pakzadeh, Ph.D., P.E., Brad Buecker, Mitchell Krasnopoler, P.E., Kiewit Engineering & Design Co.

Introduction On Nov. 3, 2015, the EPA’s long-awaited effluent limitations guidelines (ELGs) for the steam electric power generating industry were published in the Federal Register. Plants must meet the discharge limitations in this rule by the date determined by each facility’s permitting authority; within a time frame beginning Nov. 1, 2018, but no later than Dec. 31, 2023. The guidelines specifically address coal, petroleum-coke and integrated gasification combined cycle (IGCC) power plants. Oil-fired generating units and small coal plants (50 MW or less) are an exception and only need to comply with Best Available Technology Economically Achievable (BAT) limitations on total suspended solids (TSS) discharge. The primary target is larger coal-fired power plants (> 50 MW) that are equipped with wet flue gas desulfurization scrubbers and/or use water to transport (sluice) bottom ash, fly ash or flue gas mercury control (FGMC) waste. Table 1 summarizes

two control options that the EPA chose – Option D for existing plants and Option F for new sources. For the larger coal plants and other facilities being regulated, the ELG offers what seems to be conflicting requirements, as shown by the following quote from the guidelines: For fly ash transport water, bottom ash transport water, and FGMC wastewater, there are two sets of BAT limitations.The first set of BAT limitations is a numeric effluent limitation on Total Suspended Solids (TSS) in the discharge of these wastewaters (these limitations are equal to the TSS limitations in the previously established in the Best Practicable Control Technology Currently Available (BPT) regulations.The second set of BAT limitations is a zero discharge limitation for all pollutants in these wastewaters.

Figure 1. Forced oxidation limestone system process overview

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February 2016

FEATURES Table 1 – Final rule: Steam electric main regulatory options Regulatory Options

Wastewater

Option D (Existing Sources)

Option F (New Sources)

FGD Wastewater

Chemical precipitation + biological treatment

Evaporation

Fly Ash Transport Water

Dry handling

Dry Handling

Bottom Ash Transport Water

Dry handling or closed loop

FGMC wastewater

Dry handling

Combustion residual leachate

Impoundment (equal to BPT)

Chemical precipitation

So, for the first set, EPA established TSS limits of 100 mg/L (daily maximum) and 30 mg/L monthly average, but the second BAT limitations set is moving the industry to dry handling of ash (or closed loop operation for bottom ash). EPA allows the reuse of fly ash or bottom ash transport water as makeup in the FGD scrubber. For FGD wastewater, discharge limitations are outlined in Table 2. Recommended BAT technology for existing sources is chemical precipitation that may employ any or all of the following: hydroxide precipitation (lime), sulfide precipitation, iron co-precipitation, and perhaps also anoxic/anaerobic fixed-film biological treatment to remove selenium and nitrate. For new sources, evaporation of FGD wastewater is the BAT. The most popular technology is expected to be falling-film evaporation (brine concentration) that produces both a brine and distillate stream. Existing dischargers that voluntarily choose to meet more strict effluent limitations for FGD wastewater with thermal evaporation must meet such limitations by Dec. 31, 2023. The five additional years to implement this technology is an incentive for choosing evaporation, but the price tag is expensive. For combustion residual leachate at existing sources, a TSS limit of 100 mg/L (daily maximum) and 30 mg/L (monthly average) is the guideline for discharge from landfills and surface impoundments. Landfill and surface impoundment control should follow the specifications provided in the Disposal of Coal Combustion Residuals from Electric Utilities final rule, which

was signed on Dec. 19, 2014, and subsequently published in the Federal Register (FR) on April 17, 2015. For new plants, the combustion residual leachate should be handled using chemical precipitation with numeric limitations on arsenic of 11 µg/L/8 µg/L (daily maximum/monthly average) and mercury 788 ng/L/356 ng/L (daily

maximum/monthly average). According to EPA and EIA, at least 116 U.S. plants have wet FGD systems, with a total of 254 wet scrubbed generating units. The next section examines wet FGD process chemistry, followed by a comparison of evaporation and biological wastewater treatment processes, with discussion of the advantages/disadvantages of each technology.

Wet flue gas desulfurization process Coal-fired power plant combustion releases many toxic chemicals and pollutants, some of which are only in trace quantities. Along with nitrogen, excess oxygen and carbon dioxide, many of the pollutants enter the flue gas as SOx, NOx, HCl and HF. Other impurities include mercury, selenium and arsenic. A variety of flue gas desulfurization (FGD) processes is available, including wet scrubbers, dry sorbent injection, spray dryer absorbers and circulating dry scrubbers. While, as the name implies, FGD is primarily designed to remove sulfur oxides, the processes also remove other acid gases such as hydrogen chloride, and in some cases also mercury. Approximately 87 percent of all U.S. FGD systems are of the wet scrubber variety. Most wet scrubbers utilize forced-air oxidation to convert the byproduct to gypsum, but some employ inhibited oxidation. Of the wet scrubbers, the majority (70 percent) use limestone as the reagent, while 17 percent employ lime feed, with the remainder using alkali blends or rather uncommon reagents such as limestone/fly

Figure 2. Generic block flow diagram for chemical precipitation and biological treatment. Advantages and disadvantages of biological treatment processes are outlined in Table 4. February 2016 ENERGY-TECH.com

FEATURES Table 2 – Effluent limitations and standards for FGD wastewater Pollutant

Existing Sources

New Sources

Long-Term Avg

Daily Max Monthly Avg Long-Term Avg Daily Max Monthly Avg

Arsenic, total, µg/L

5.98

4.0

N/A

Mercury, total ng/L

159

788

356

17.8

5.0

N/A

Selenium, total, µg/L 7.5

ash, lime/fly ash, magnesium-enhanced lime, magnesium oxide, soda ash, etc. Most forced oxidation scrubbers have limestone as the reagent of choice. Limestone (primary component is calcium carbonate [CaCO3]) reacts with sulfur dioxide (SO2) that is hydrated in the scrubber to produce an initial calcium sulfite hemi-hydrate (CaSO3∙½H2O) solid. In forced-oxidation units, compressed air is constantly injected into the slurry to convert the sulfite to gypsum (CaSO4∙2H2O). The remainder of this discussion focuses on forced-oxidation scrubbers, and a schematic of the process is shown in Figure 1. Although gypsum is the primary end product, the slurry and scrubber liquor also contain dissolved calcium, sulfate, chloride, and other compounds, including inert materials introduced from the limestone. In almost all systems, flyash is removed from the flue gas upstream of the scrubber. The absorber is the heart of the process, and here fresh limestone and partially-reacted products are continually recirculated, with the slurry being sprayed from above to counter-currently contact upwards rising flue gas. A bleed stream of slurry, at about 15-20 percent suspended solids concentration, is taken from the absorber and partially dewatered in hydrocyclones followed by

rotary drum or belt filtration to produce a gypsum “cake” with a moisture content of 10-15 percent. All wet FGD systems must have a purge stream, primarily to control chloride concentrations. Often this concentration is limited to 12,000-15,000 mg/L due to corrosion potential in the scrubber, but the concentration can be higher if the vessels are fabricated from or lined with high-nickel alloys.

Wet FGD wastewater characteristics Table 3 provides a typical composition of the wet FGD wastewater stream. The amount of suspended solids depends on the clarification step. As Table 3 indicates, a variety of impurities typically exist in wet FGD wastewater, whose potential treatment methods are outlined next. Chemical precipitation and biological process EPA’s BAT for FGD wastewater recommends chemical treatment that may employ hydroxide (lime) precipitation, sulfide precipitation and iron co-precipitation for metals removal, followed by anoxic/anaerobic fixed-film biological treatment for selenium and nitrate control. Currently, six U.S. steam electric

Table 3 – Forced oxidation wet FGD wastewater characteristics Constituent

Units

Range

TDS

mg/L

10,000-50,000 N/A

N/A

Alkalinity as CaCO3

mg/L

20-300

N/A

Calcium

mg/L

750-8700

N/A

Magnesium

mg/L

500-1,800

N/A

Sodium

mg/L

30-600

N/A

Sulfate

mg/L

1,300-3,600

N/A

Chloride

mg/L

800-37,000

N/A

Boron

mg/L

30-900

N/A

5.5-8.0

6.0-9.0

N/A

Monthly Average Limitation for Existing Sources

Required Removal

TSS

mg/L

10-40,000

0-99.9%

Nitrate/Nitrite as N

mg/L

10-100

4.4

56%-95.6%

Arsenic

µg/L

10-500

20%-98.4%

Selenium

ng/

50-3,900

76%-99.7%

Mercury

ng/L

100-20,000

356

0-98.2%

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February 2016

FEATURES Table 4 – Advantages and disadvantages of biological treatment processes Advantages

Disadvantages

Proven technology

Physical/chemical pretreatment required: Biological treatment for polishing

Automation is relatively simple and reliable

Sensitive to temperature changes, high chloride concentrations, scaling, high oxidation-reduction potencial (ORP)

Low hydraulic retention times

Microorganisms maintenance (nutrients are required) Waste sludge can have a low settling rate

power plants use biological treatment for nitrate and selenium control in FGD wastewater. Biological processes require extra operator attention to maintain healthy microorganisms employed in the process. The “bugs” are sensitive to temperature changes, high chloride concentrations, scale formation, high oxidation-reduction potential (ORP) in the wastewater, and cycling operation. Typical process constraints are temperature range of (40°F to 105°F), chloride < 25,000 mg/L, TSS < 250 mg/L, nitrate-N < 250 mg/L, and pH range of 6 to 9. High ORP, which is a function of forced-air oxidation, requires pretreatment ahead of microbiological reactors, which, as previously indicated, operate anoxically and anaerobically. Feed of a reducing agent ahead of the biological reactor also might be required. Monitoring of ORP adds to operational complexity of biological systems. Cycling operation and extended or even short shutdown periods can kill microorganisms, so layup/startup procedures must be in place to maintain healthy colonies. One technique is to circulate water and feed the organisms with a supplemental source, such as molasses. The combination of chemical precipitation followed by anoxic/anaerobic fixed-film biological treatment can achieve removal efficiencies of more than 99 percent for mercury, selenium and nitrate/nitrite, and 95 percent for arsenic. Current proven technologies are GE ABMET® and Suez iBio®. Figure 2 presents a generic block flow diagram for chemical precipitation and biological treatment.

Evaporation processes For new plants, EPA established BAT limitations for FGD wastewater recommend falling-film evaporation to produce a concentrated brine and a distillate stream. Pretreatment by chemical precipitation is generally required to reduce the potential for scale formation in the evaporator. Reputable falling film evaporator vendors include Aquatech,Veolia, GE and GEA. To reach zero liquid discharge (ZLD) outside of deep-well injection or evaporation ponds requires additional thermal treatment, and this can be a very difficult proposition with FGD wastewater. Only a few systems are in operation around the world. One possibility is forced-circulation crystallization, but this requires very exotic materials of construction for corrosion control. Energy requirements and prevention of scale formation are other critical issues. A substitute for crystallization is spray drying utilizing hot flue gas. The process is appealing because the energy source (hot gas) is free as long as solid handling issues are carefully considered and resolved. One potential configuration uses a hot gas slip stream to dry the wastewater, with exhaust gas return upstream of the plant’s existing particulate collection system. Another alternative is a partial zero-liquid discharge system that concentrates the pretreated wastewater using a falling film evaporator. The concentrate can then be mixed with fly-ash (and lime) in a pug mill to produce a solid product. Solidification and stabilization is an important process to fixate metals within the solids and minimize leachability. Table 5 summarizes advantages and disadvantages of this process.

Table 5 – Advantages and disadvantages of ZLD evaporation/crystallization Advantages

Disadvantages

Evaporation separates all dissolved species and forms a stable solid for landfill

Extensive physical/chemical pretreatment required

Distilled water is high purity and can be reused

Very high OPEX (high reagent costs) and CAPEX

With crystallizers, no wastewater is produced

Hard to operate High electric power requirement for evaporation Stringent maintenance requirements

February 2016 ENERGY-TECH.com

FEATURES A key disadvantage of the evaporator/crystallizer system is high capital cost. One method to reduce cost is to pre-treat and reduce the volume of the stream by (innovative) membrane technologies. Such designs are the vortex generating membrane system (from BKT) and vibratory sheer enhanced processing (by New Logic Research Inc.). Reverse osmosis is another possibility for waste stream reduction, although membrane selection and pre-treatment chemistry are critical items.

Summary FGD wastewater process chemistry is very complex. Design engineers must have a good understanding of the FGD process to predict water chemistry changes and design variations in FGD wastewater treatment systems. The fuel source, makeup water chemistry, scrubbing process and other plant processes should be studied in detail prior to FGD wastewater treatment design. Several technologies are proven to remove arsenic, mercury, nitrate/nitrite, and selenium from FGD wastewater. Process guarantees are very important when selecting technologies. Equipment availability and redundancy, effluent quality, leachability of sludge, and water reuse potential should be considered carefully. Solids stabilization is an important process to fixate metals within the solids and minimize leachability.

References 1. Kyle Smith, Antonio Lau, and Fredrick Vance; “Evaluation of Treatment Techniques for Selenium Removal,” IWC September 2005. 2. Thomas E. Higgins; A. Thomas Sandy, PE; and Silas W. Givens, PE Flue Gas Desulfurization Wastewater Treatment Primer, Power 3. Aquatech website, GE website, Veolia Website 4. Stephen E. Winter, et. al., “Preliminary Results from a WFGD Effluent Characterization Study and their Impact on Scrubber Operations and Waste Water Treatment,” Paper # 140.) 5. Shaw W. (2009), “New Low-Temperature ZLD Process”, International Water Conference, Paper IWC 09-52 Behrang (Ben) Pakzadeh, Ph.D., P.E. (licensed in California), is a senior process engineer with Kiewit Engineering & Design Co. He has more than 10 years of experience in power, upstream oil-and-gas, and municipal water and wastewater industries. Pakzadeh serves on the Water Environment Federation (WEF) Industrial Wastewater Committee. He has a Ph.D. in civil and environmental engineering from the University of Nevada – Las Vegas, a master’s degree in environmental engineering from Technical University of Denmark, and a B.S.C.E. from Sharif University of Technology (Iran). You may contact him by emailing editorial@woodwardbizmedia.com. Mitchell Krasnopoler is Kiewit’s manager of Air Quality. He leads Kiewit’s design of emission control systems and presents Kiewit’s AQCS capabilities to customers. He is responsible for Kiewit’s emission control program, including studies, conceptual, preliminary and detailed design, as well as startup and performance testing. He has more than 24 years of engineering experience in emission control technologies and extensive experience in flue gas desulfurization (FGD) design, operations and testing. He has written several technical papers on various emission control technologies. Krasnopoler previously was Bechtel’s Manager of Air Quality Control Systems. You may contact him by emailing editorial@woodwardbizmedia.com. Brad Buecker is a process specialist in the Process Engineering and Permitting group with Kiewit Engineering and Design Co., Lenexa, Kan. He has more than 33 years of experience in, or affiliated with, the power industry, much of it in steam generation chemistry, water treatment, air quality control and results engineering positions with City Water, Light & Power (Springfield, Ill.) and Kansas City Power & Light Company’s (La Cygne, Kan.) station. He has a bachelor’s degree in chemistry from Iowa State University, with additional course work in fluid mechanics, material and energy balances, and advanced inorganic chemistry. He is a member of the ACS, AIChE, ASME, CTI and NACE, the ASME Research Committee on Power Plant & Environmental Chemistry and the program planning committee for the Electric Utility Chemistry Workshop. You may contact him by emailing editorial@woodwardbizmedia.com.

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February 2016

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FEATURES

A people-centered approach to lowering weld rejection rates By John E. Miller, Day & Zimmermann

During a typical outage or project at nuclear and fossil power plants, welders make thousands of individual welds on key pieces of infrastructure. Although required inspection methods and weld acceptance criteria vary, minimizing rejection rates for all welding activities is critical to schedule and budget predictability. Rejected welds that are not identified and corrected can impact plant reliability and lead to costly forced outages. The solution to this problem is not as simple as finding good welders. The pool of highly-experienced welders has dwindled in recent years as workers have aged and retired. In this environment, plant managers must look for contractors who have and use systemic processes to maximize existing talent and also implement checks and balances to ensure new talent is being developed and monitored without sacrificing productivity or quality. While a small percentage of weld rejections can be expected on projects, high rejection rates lead to potential schedule delays and increased costs. The following

four elements are essential in developing a welding program that minimizes rejection rates. They focus on both the technical aspects of welding, and on the people and processes behind the final work product. This approach has enabled Day & Zimmermann to keep its average rate as low as less than 1 percent.

Test, test and test again Some say that welding is an art rather than a discipline. It requires certain fine motor skills, good eye-to-hand coordination, and intense mental focus and concentration. The most difficult welds require a high degree of precision. Not all welders possess the same level of skill, and even the best welders’ skills diminish with time or periods of inactivity. As welders age, their eyesight may begin to deteriorate and their hands might not be as steady. That’s why a contractor’s pre-work testing procedures are critical in minimizing weld rejections.

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FEATURES Baseline qualifications and experience requirements will help weed out the truly incapable, but all new welders should be required to take additional provisional tests before beginning work, regardless of current certifications. Tests should be challenging enough to match the actual work that will be required. Even if a contractor is familiar with a particular worker from previous projects, these tests are necessary to re-confirm skill levels. Only by testing everyone can contractors get a full picture of the available talent.

Use practice to make welds perfect Once talent is evaluated, it’s the contractor’s job to put that talent in the best position to succeed. While assigning the most skilled welders to the most difficult jobs helps to minimize rejection rates, all welders can benefit from additional practice and planning. Many fossil plant welds are made in particularly tight spaces or precarious positions. Effective welding programs plan for difficult welds. This planning should include mock-ups or test runs of challenging welds in simulated scenarios. While this may seem like an additional cost and a time-consuming step, difficult or limited access welds will not be easy to re-work in a real world scenario. The test environment allows workers to refine their skills before beginning the work.

lagging indicators will not undo rejected welds, but by looking at weld rejection data, contractors can identify trends and uncommon trouble spots. This information can be used to develop new best practices and techniques. Contractors should be able to demonstrate a history of low weld rejection rates and also share lessons learned with plant managers before beginning a new project or outage. Plant managers should inquire about the way contractors track rejected welds to make sure numbers they are providing give an accurate picture of weld rejection rates. To understand the importance of weld quality management, the power generation sector can look at news from the last few years in the midstream energy sector. In 2014, the number of rejected welds on the Keystone XL pipeline was called into serious question. It was a public relations nightmare for the project and a legitimate examination of the dangers of poor welds. In power generation, the stakes of poor welds are just as high, if not higher. For these reasons, plant managers must look beyond reported percentages to find contractors that effectively manage people and processes. John E. Miller is the director of Quality Assurance and Control at Day & Zimmermann. You may contact him by emailing editorial@woodwardbizmedia.com.

Inspect early and often Contractors provide the most value in minimizing weld rejections when inspections/examinations are conducted early in the project. A rejection rate of zero is almost unheard of, but keeping rejections close to zero is possible with the proper oversight from quality control managers. QC personnel need to take a proactive approach in overseeing the welding activities in the field. If they let inexperienced or even veteran welders make too many welds before making an inspection, it could lead to much higher rejection rates. A good rule of thumb is to limit the number of welds to a small number before inspections are made. Open and Non-Intrusive Flow Measurements timely communication between QC and in the HRSG Industry Production Management is essential. Once the first inspections are completed, it should t Highly accurate and reliable flow be followed by aggressive management and measurement up to 750 °F t No process stops for installation daily oversight. Multiple weld inspection t Virtually maintenance free methods, including in-process and final t Decreased downtimes and forced outages visual inspections and examinations, should be employed to confirm weld acceptability.

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MAINTENANCE MATTERS

Managing generation assets under changing mission profiles By Ray Chambers, Revis James and Norris Hirota, Electric Power Research Institute (EPRI)

Today many central-station generation assets — including fossil, hydro and nuclear plants — are experiencing significant changes in their operating missions compared to their original designs. These changes include new operating regimes with increased cycling, extended unit layups and prolonged periods of low turndown. The changes, in turn, are creating a multitude of issues for the plants and their operating staff in areas ranging from component degradation to staffing levels, O&M budgets and meeting environmental compliance under non-baseload conditions. To help the utility industry address these challenges, the Electric Power Research Institute (EPRI) launched a broadbased, multi-utility research project, consisting of several individual power plant studies and an industry working group. The project, called “Changing Mission Profiles,” is aimed at better understanding the issues and finding economically and technically sustainable solutions. This new project is designed to be comprehensive, covering all types of unit and mission combinations, to take a unit- and fleet-level view, and bring together cross-disciplinary technical expertise.

Challenges of new duty modes Flexible operation of power generation assets is not new. However, over the past decade – and particularly in the last few years – a number of factors have combined to increase the levels of flexible operation and the number of baseload plants required to change their operating missions. The factors include more demand response, lower gas prices and increased coal-to-gas switching, aging plants and plant retirements (increasing limited dispatchable resources), stricter environmental controls, and increased deployment of intermittent renewable generation that is dispatched as “must-take.” In this context, relatively small differences in a plant’s cost, reliability and availability can bring large changes in station ranking, dispatch order, and operating mission profiles. EPRI recently published the results of a two-year study, jointly funded by the U.S. DOE, indicating that future levels of necessary flexible operations are likely to be very significant. Flexible operation is typically defined as any mode of operation other than baseload and includes several specific types of duty modes. Two-shifting is starting up and shutting down a plant each day to meet load demand during periods of high demand.

Figure 1 Priorities by unit design / mission profile. February 2016 ENERGY-TECH.com

MAINTENANCE MATTERS Double two-shifting is starting up and shutting down a unit twice a day, regularly to match the early morning and evening peaks in load demand. Load following is operating online for more than 48 hours, with varying load throughout the day as demand changes. Minimum load operation is operating a unit at the lowest output technically possible for prolonged periods of time, often as a result of variable generation from renewable resources. Due to changing dispatch patterns, extended periods of unit shutdown between operating periods are occurring. This is typically referred to as “extended layup.” While these modes are not new, what is new is the frequency and level of cycling required. Operational flexibility also entails addressing new challenges created by off-baseload operations, such as maintaining selective catalytic reduction (SCR) performance at lower temperatures, coping with new chemistry conditions created by different and changing coal blends, etc. The characteristics of flexible operation — more frequent startups, faster ramping, low-load operation and longer layups — can stress plant systems and operations. For formerly base-loaded coal-fired plants, the new duty cycles force plant equipment to be operated closer to, or beyond, nominal design limits and through more thermal cycles than originally anticipated. The

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consequences can be increased rates of high-temperature component life-consumption, increased wear-and-tear on balanceof-plant components, decreased thermal efficiency at low load, increased fuel costs due to more frequent unit starts, difficulties in maintaining optimum steam chemistry, potential for catalyst fouling in NOx control equipment, and increased risk of human error in plant operations. Combustion turbine combined-cycle (CTCC) plants typically have less operating flexibility than conventional steam plants, which can be run down to 40 percent of rated output, while CTCC plants have difficulty in getting below 60 percent. A further problem is the length of time that it takes for the heat recovery steam generator (HRSG) plant to achieve full output. Hence, although a CTCC plant might be able to produce power relatively quickly, it is not really suitable for load-following until sometime after startup. Research shows common damage mechanisms in CTCC plants related to cycling include thermal fatigue, differential thermal expansion, corrosion, increased tube leakage and impaired performance of environmental control equipment. For any plant type, other changes brought about by flexible operation can include decreasing revenue, increased complexity for plant staff and uncertainties in fuel procurement. The current issues for different types of generation are shown in Table 1.

February 2016

MAINTENANCE MATTERS Table 1 – Key Aspect of Generation Types Realtive to Flexible Generation Generation Type

Positive Attributes

Negative Attributes

Future Prospects

Subcritical Drum Boilers

Flexible to low load

Smaller size, old retrofit of environmental controls typically not cost effective

Retiring without environmental retrofits, not viable in longer term

Supercritical

Efficient at baseload, flue gas treatment on larger units deemed appropriate

Not designed for Flexible operations flexible operations, causes damage unstable at low loads, environmental controls less effective or not functional at low loads

Combined Cycle

Efficient, more flexible in relation to coal units

Typically designed for limited hours of operations (e.g., peaking). Flexible operations cause damage in heat recovery steam generators (HRSGs)

Nuclear

Designed for high Operational flexibility capacity factor, base- capabilities are very load operations limited and typically can only occur over mult-day timeframes or longer

Operating flexibility research In recent years, EPRI has conducted a wide variety of research efforts related to operating flexibility. For example, an EPRI study identified cost-effective modifications to equipment and operating procedures that could reduce heat rate and recover plant efficiency lost to continuous cycling operation. New cycle chemistry guidelines were compiled for all transient operations, including specific procedures during cycling, shutdown, startup and layup for each boiler and feedwater treatment, and covering all major water- and steam-touched surfaces. Using the experiences of the fossil fleet in the United Kingdom, which transitioned from baseload to flexible operation in the 1990s, EPRI published a Flexible Operations Readiness Guide. The guide shares lessons learned about the equipment, systems and processes affected by increased cycling. A study of the low-load performance of selective catalytic reduction (SCR) systems used for NOx control helped to identify operating procedures to improve plant turndown at minimum load periods without impairing SCR performance and without forcing units to cycle-off. Another project developed a systematic process to operate units at a sustainable minimum load for extended periods and developed a Minimum Load Web Tool to aid in the operational testing to achieve a low minimum load.

More baseload use due to lower fuel cost, but better HRSG designs needed

Research assessing increasing nuclear flexible operations is being conducted, but minute/hourly flexibility will not be possible with nuclear assets

In all, EPRI has completed or embarked on more than 50 major R&D efforts related to operational flexibility of existing fossil plants.

Need for more comprehensive approach This research has been invaluable in helping utilities individually address the many issues related to increasing operating flexibility. However, during the past year discussions between EPRI members and EPRI research staff also identified several needs that require a more holistic research approach to be adequately addressed. One need was to coordinate research in different disciplines — including O&M, boilers, turbines, environmental controls, plant chemistry and material science — and to study plants from these multiple perspectives. EPRI observed that implementation of multiple solutions to different issues can create unintended consequences. Another need was to gather experience for all the different combinations of unit designs and mission profiles (e.g., supercritical coal + minimum load operation).

Yet another need was recognizing that unit- and fleet-level issues of flexible operations are linked. That is, addressing unit-level issues created by changing mission profiles will help in planning operational flexibility for a future fleet. Insights into unit-level flexible operations can inform asset management strategies at the fleet level in areas such as plant operations and design, staffing and implications for the power grid. In parallel with this acknowledgment of unaddressed needs, generation planning research, funded jointly by EPRI and the DOE, was conducted into the effects of operating flexibility on dispatchable assets. Findings suggest that the extent and diversity of increased flexible operations will be profound during the next 20+ years. The majority of dispatchable units will experience the necessity for flexible operations, and possibly multiple mission profiles. Flexible operations also will be geographically widespread; most power companies will have to support multiple mission profiles across their fleets in managing current and future assets. According to this same research, flexible operations are the principal challenge arising from increased variable generation, and key challenges are operations at minimum loads and significant amounts of ramping at high rates. The study also projected frequent, large changes in average hourly generation for CTCC and coal assets, as well as significant periods of low-load operations and reserve standby.

February 2016 ENERGY-TECH.com

REGULATIONS COMPLIANCE Changing mission profiles project To address the needs previously described and prepare for future developments in the industry, EPRI launched a major collaborative, two-year effort, called the Changing Mission Profiles Project. The project brings together 14 generating companies, representing all central-station generation types. The project has two main components: (1) a series of Pilot Projects that conduct onsite plant visits to study different unit types and identify key issues, and (2) a Working Group that convenes subject-matter experts (SMEs) and utilities to identify effective solutions and mitigation strategies. The project’s goal is to develop technical guidelines and an industry database of issues and solutions that allow power companies to sustainably manage flexible operations for current and future central generation assets. An important aspect of the project is fostering collaboration and a willingness to share results and lessons learned.

Pilot projects The Pilot Projects, which were initiated earlier this year, are undertaking a series of comprehensive “deep dives” into technical issues related to different specific central generation units’ transition to new missions. The approach consists of onsite visits by SMEs from EPRI to meet with utility SMEs to discuss actual experience of units managing significant flexible operations. To date, site visits have been conducted for several unit/mission combinations: • Subcritical pulverized coal (PC) unit/load following • Supercritical PC unit/minimum load and extended layup • Two gas boilers/load following and layup • Combustion turbine — combined cycle/transition from cycling to baseload • Hydro/cycling Future plant visits will include subcritical two-shift PC. The site visits use a standardized process to identify, discuss and prioritize key technical issues for that unit/mission config-

uration. For each issue, the process captures critical assumptions, options and tradeoffs, key interrelationships, vulnerabilities, unanticipated consequences, and gaps and uncertainties in industry knowledge and understanding. Resulting from these visits is a ranking of technical issues related to plant operations, equipment and environmental controls. For each unit/mission, experts and stakeholders apply evaluation criteria to the issues via a template. The criteria for ranking include: • Impact on corporate metrics — How does this issue affect corporate performance and related metrics? • Acceptable options available — Are there good solution alternatives? • Technical resources available — Are solutions available through EPRI or other organizations? • Degree of uncertainty — Do we understand the technical basis for the issue and for the solution path forward? • Impact on plant staff and O&M — How will the solution to the issue be sustained and affect the plant staff? An example is shown in Table 2. To date, the site visits have produced a number of key priorities as seen by industry experts: • Minimum load operational issues need attention. • Combination of low load and the need for fast ramp rates is a significant challenge. • Flue gas desulfurization (FGD), selective catalytic reduction (SCR), and other environmental control equipment issues have high priority. • Greater guidance is needed where layup duration is uncertain. • Budget uncertainty limits available options. • Impacts of key issues on plant staff are expected to be significant. • Having a cross-functional, multi-discipline team to evaluate issues and unanticipated consequences is valuable.

Table 2 – Changing Mission Profiles Pilot Project: Sample Output Assessment Criteria (level of impact: high = 5, medium = 3, low = 1) Techical Issue

Impact on Business Metric?

Acceptable Options?

Available Degree of Technical Uncertainty? Resources?

FGD pluggage due to solid scales

Corrosion fatigue in waterwalls

Impact on Plant Staff?

Estimated Overall Impact?

Extreme loads may reduce ramp rate

SCR temperature dependency (low load)

High sulfur effects on filter bags

Impact on boiler tube corrosion

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February 2016

MAINTENANCE MATTERS Working group The Mission Profiles Working Group provides a cross-disciplinary forum of subject-matter experts to review the results of the Pilot Project site visits, and to identify issues and solution options. Experts are from six technical areas: combustion/environmental controls, boiler and chemistry, O&M/balance of plant, turbine generator, combustion turbine/HRSG and hydropower. Meetings are being held quarterly over the next two years. To date, two meetings have been held.

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Already in early meetings of the Working Group, priorities have begun to emerge among the issues of operating flexibility (see Figure 1): • •

Pulverized coal — highest interest in low turndown for both subcritical and supercritical units; and SCR operations at low load. Oil/gas boilers — priorities are low turndown, then ramp rate improvement and shutdown.

The Working Group concept is based on the premise that high value can be realized from the real-time sharing of the collective knowledge and expertise of the industry to supplement and inform EPRI research. As it identifies issues, the Working Group process will seek to determine if relevant existing EPRI or other industry (DOE, OEMs, vendors) research results are available to address the issue, or if future immediate or longer-term R&D is needed. Ray Chambers is the program manager of EPRI’s Generation Maintenance Applications Center (GenMAC). His background includes 23 years with Progress Energy as a manager in various O&M management positions. You may contact him by emailing editorial@woodwardbizmedia.com. Revis James is a director in EPRI’s Generation Sector, with responsibilities in several research programs, including advanced coal generation, steam turbine-generators, boiler life and availability, and large-scale industry demonstration projects. You may contact him by emailing editorial@woodwardbizmedia.com. Norris Hirota is a director in EPRI’s Generation Sector, managing technology development programs for power plant operations, maintenance, materials, chemistry, and environmental controls. You may contact him by emailing editorial@woodwardbizmedia.com.

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TURBINE TECH

Outage planning – Best practices and steps you can’t afford to skip! By Steve Reid, PE, and Tom Reid, TG Advisers Inc.

As turbine generator consultants with plenty of lescurement of material in anticipation of repair can avoid costly sons-learned experience, a question often posed to our firm is, expediting charges for parts that might not otherwise have been “How can our plant improve its outage execution?” This is a ordered until the outage occurs. Since outage reports do not reasonable question. Through the years we have seen everything document the full extent of unit issues, TGA has found plant from flawlessly executed outages to outages ending in the corsite interviews with key maintenance and operations’ personnel helpful in identifying undocurect season but wrong year. mented concerns that should be So how do you optimize addressed during the overhaul. outage performance? From Join us for our Energy Tech - TG The pre-outage process also our experience, it boils down should consider a review and to upfront preparation and Advisers “Secrets to Executing a risk rating of all applicable unit contingency planning, proper Successful Turbine-Generator technical advisories. A percentengagement during the outage of the advisories are meant age, and often overlooked but Outage”, online training to alert plants of pending availessential post-outage activities. Feb. 16-18, ability issues and might include This article will introduce you to best practices and tools we to learn more about steps and tools recommended parts replacement during a major outage. have seen over the years. for effective outage performance. These advisories should not be Pre-outage activities Visit www.energy-tech.com/outage ignored in the planning process! It also is valuable to comMajor turbine generato learn more and register. plete a thorough pre-outage tor outage planning should operational data review to begin 18-24 months prior to identify any abnormalities that commencement. Reviewing should be integrated in to the outage scope. This effort also proall available prior outage reports and summarizing major issues vides an opportunity to benchmark pre-outage operational data. are important in the pre-outage phase. Report analysis should TGA typically evaluates startup events – paying attention to key include noting any irregular findings or damage trends. Trends supervisory instrumentation variables such as vibration, bearing of parts replacement and chronic component cracking concerns temperature, differential expansion, etc. In addition, this process should be highlighted and plans developed to address these affords an opportunity to perform good post-outage comparison issues. Examples for concern are bolt cracking, bearing damage data that can be used to benchmark the success of the overhaul. or excessive blade path erosion. Contingency planning and pro-

Figure 1. Effective QA-QC Sheets allow the owner’s representative to operate like a seasoned veteran by capturing lessons learned and experience in the comments

20 ENERGY-TECH.com

February 2016

TURBINE TECH Don’t forget to factor in the changing duty cycle! With a continually changing energy marketplace, turbine generator units have seen a large shift in duty cycles over recent years. For many units, this has meant an increase in start-stop low fatigue cycles and a reduction in minimum load during off-peak hours of operation. These changes in operation will increase maintenance costs and expand past baseline outage scopes and parts supply requirements. The outage scope must include a more aggressive plan for inspections focusing on low cycle fatigue damage areas; such as bore, LP blade attachment phased array, and case cracking. Cycling also will increase boiler particle exfoliation, which in turn will increase solid particle erosion rates of the turbine blade path. This could accelerate blade replacement schedules due Figure 2. Pre-outage operational data assessment. to increased water droplet eroDuring large outages, internal resources are almost always sion of the LP blade path. Again stretched thin. This is where outage execution tools play an blade replacement schedules might need to get more aggressive important role. Two examples include critical outage charting depending on the time operating at lower loads. templates and QA/QC checklists that are discussed below. Also, plan to wrap up your preparation and final scope Development of blade path and assembly charting temdevelopment activities with readiness review meetings with both plates prior to the outage have proven to be a valuable “on the internal and external key personnel. floor” tool. Templates typically include alignment data, oil bore readings and blade path radial and axial clearances. The template Outage steps for success should be populated with prior outage information to support Prioritize and complete critical NDE inspection and genera quick interpretation of the data and the ability to discuss and ator testing as soon as feasible. This allows for required repair or make changes with minimal impact on schedule. Don’t wait for replacement assessment work to be completed in parallel with a failed startup to review this data. At this point, issues are very other outage activities. Thorough contingency planning will costly to correct. minimize any disruption in schedule.

Figure 3. Pre-outage risk assessments should be completed on the entire unit to prioritize activities.

February 2016 ENERGY-TECH.com

TURBINE TECH TGA views QA/QC sheets as an integral but continuously evolving outage document. The ultimate goal of these sheets is to give the owner the opportunity to track progress, completeness and evaluate quality during key points of the outage. An effective program should go well beyond the steps of the work scope by allowing the responsible plant engineer the ability to operate with the knowledge of a seasoned veteran, regardless of experience. After the outage, the checklists need to be updated to incorporate lessons learned, any future recommended inspections and key review points.

Post outage assessment and lessons learned capturing Outages typically drain plant resources with long days and weeks of outage activities. The conclusion typically signals a time to catch up on day-to-day plant work orders and common operational responsibilities. However, failing to capture lessons learned and best practices while they are still fresh is a missed opportunity to continuously improve a plant’s outage process and resulting performance. Based on inspection findings, future maintenance intervals should be reevaluated. It might be appropriate to increase or decrease outage frequency and budgets based on identified risks and condition assessments. Predictive maintenance programs should be renewed and any life assessment analysis required from the outage inspection findings should be competed in a timely manner.

As noted earlier, TGA strongly recommends a post outage operational assessment to identify any significant changes from the pre-outage assessment. Also, confirm all outage goals have been met. Post outage lessons-learned meetings should be standard operational practice! Stephen R. Reid, P.E., is president of TG Advisers Inc. and has more than 30 years of turbine and rotating machinery experience. Reid and his team provide turbine troubleshooting, health assessments and expert witness services to major energy companies in the U.S. and have provided condition assessment evaluations on more than 100 turbine generators in the U.S. Reid also is a short course instructor for EPRI, ASME, Electric Power and POWERGEN, has numerous patent disclosures and awards, and published more than 20 technical papers and articles. Reid was the recipient of the 1993 ASME George Westinghouse Silver Medal Award for his contributions to the power industry and is past chairman of the ASME Power Generation Operations Committee. He is a registered professional engineer in the state of Delaware. You may contact him by emailing editorial@woodwardbizmedia.com. Tom Reid is a consulting engineer for TG Advisers Inc. Reid and team provide engineering services to gas turbine, steam turbine, and generator users worldwide. Reid is a graduate of General Electric’s Edison Engineering Development Program and has numerous patent disclosures related to turbine design and advanced gas turbine repair technology. He holds a bachelor’s degree from Virginia Tech and a master’s degree from Georgia Tech. You may contact him by emailing editorial@woodwardbizmedia.com.

Figure 4. Templates generated pre-outage allow for quick data review vs. design and historical readings.

22 ENERGY-TECH.com

February 2016

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ASME FEATURE

The impact of qualified bolting specialists on the safe, reliable assembly and operation of bolted flanged connections By A. Fitzgerald (Jerry) Waterland III, VSP Technologies; David Lay, Hytorc; and Michael Dodge, ASME

The history of ASME involvement in setting standards for pressure vessels and piping goes back more than 130 years to the 1880s. In fact, the very first two standards approved were “Code for the Conduct of Trials of Steam Boilers” (1884) – the first Performance Test Code – and “Standard for the Diameter and Overall Dimensions of Pipe and Its Threaded Ends” (1886-87). These standards were the first in a long line of critically needed safety and design guidelines for pressurized systems that have saved lives and improved the quality and efficiency of industrial production and maintenance around the world. However, it was not until the 1980s that a separate Pressure Vessels and Piping Division (PVPD-1983) was created and charged with the management of ASME activities related to codes, standards, guidelines and accreditation programs directly applicable to non-nuclear pressure containing equipment. The PVPD established the Pressure Technology Post-Construction Committee (PCC-1995) to develop and maintain standards for maintenance and repair of pressure vessels and piping covered by the standards. The Post Construction Committee further concentrated its efforts on bolted joint connections by establishing the PostConstruction Subcommittee on Flange Joint Assembly in 1998, charging it with developing and maintaining specific guidelines on bolted flange joint assembly to promote a high level of safety and leak-tightness integrity for both new and existing equipment and piping. The Subcommittee published its first edition of “Guidelines for Pressure Boundary Bolted Joint Assembly” PCC-1 in 2000, with subsequent revisions in 2010 and again in 2013. One of the significant changes in the 2013 edition was the establishment for the very first time of uniform criteria for the training and qualification of bolted flange joint assembly personnel in Appendix A.1

for accepting and implementing these recommendations remains with industry on a voluntary basis in its own self-interest. We hope that this brief review of the subject will help convince all of the interested parties to adopt the Appendix A recommendations and begin to benefit from a greater investment in the people we depend on for safe, leak-free connections. There are several features of the program that deserve mention:

Scope and authority As needed and advisable as the training and qualification of bolting personnel might be, it should be noted that even though PCC-1-2013 and its Appendix A were approved as an American National Standard, as its title declares PCC-1 is a “guideline,” and not a mandatory regulation or code. Appendix A lays out the goals and sets the recommended requirements to permanently raise the bar for the training and qualification of workers in this under-appreciated craft. But the ultimate responsibility

ASME Training and Development has put forward its own proprietary version of the Appendix A qualification program, which features a “blended learning” approach involving both web-based technical training and testing, as well as hands-on practical assessment confirming that the necessary skills and knowledge have been learned and are demonstrated. It is this ASME training program and its benefits that will explored in this paper.

24 ENERGY-TECH.com

- The qualification of Bolting Specialists is a guideline and not a requirement. - The qualification program has been purposely established as one of qualification (certificate program) not a personnel certification. The primary distinction is that no claim of worker competency for any specific work is implied, and the extent of program implementation and requalification requirements are left to the discretion of the employer rather than being dictated by an outside third party. 2 - This qualification program will ultimately involve three levels of qualification – Qualified Bolting Specialist, Qualified Senior Bolting Specialist, and Qualified Bolting Specialist Instructor. - The qualification is awarded to the individual worker and is portable, not company-specific. - Many interested organizations (such as trade schools, colleges, apprentice programs or industrial training departments, etc.) may offer Appendix A qualification and training, but their programs must be accredited by an independent review organization for compliance with the standard.

ASME Power Division Special Section | February 2016

ASME FEATURE The need for training Why should industry be concerned with improving the skills of bolted joint assemblers, especially those who work on pressurized systems? Every manager responsible for production or operations is constantly faced with demands in three key areas, safety, quality and adherence to schedule. Bolting activities are central to the success of all three of these priorities in significant ways. Safety – Bolted joints are virtually everywhere throughout industry. Bolting work is almost unique in that it puts people with powerful tools in places that can be hot, hazardous, confined or elevated. Although industry-wide data on the cost of accidents and losses due specifically to flange leakage is not available, the costs of attributable major refinery fire incidents in the hydrocarbon-chemical industry includes $80M (USA), $65M (Italy), $136M (Mexico) and $60M (Saudi Arabia), just to name a few.3 Perhaps of greater concern than the big incidents is the general resignation with which small leaks are accepted as an inevitable fact of life, when the tools and technologies are readily available to eliminate virtually all pressure boundary leaks. Safety is more than just no accidents. It extends also to health and environmental concerns, the effects of which can extend far beyond the fences around a facility. What does a lost time accident or a reportable spill cost a company today? Quality – This term can also have multiple meanings, some of which go beyond the salability of product. One definition of quality for the power industry is extending the time between planned outages and avoiding production interruptions due to leaks, vibrations or misalignments. Once an industrial process is started, it often must run for months without maintenance. The life of critical machine parts can be extended and the productivity of the equipment can be enhanced if it is assembled to manufacturer’s specifications each time it is repaired or restarted. Many industrial processes are worth millions of dollars per day and the ability to extend their effective life, and the time between planned outages, is therefore worth millions too. What is it worth to your company or manufacturing site to be able to extend the time between planned outages, or to avoid an unplanned shutdown? Schedule – Meeting a schedule often means reducing the process downtime once a shutdown, planned or unplanned, has occurred. An investment in new tooling and training can be paid back in just a few hours of increased production, made possible by faster and better methods. Bolting is always in the critical path for maintenance. Before pressure vessels can be cleaned, repaired or replaced during scheduled or un-scheduled maintenance, flange connections on the equipment and associated piping must be unbolted. As soon as the vessel is repaired, it must be reconnected, again with bolted flanged connections. Therefore every hour saved on either end of the repair falls directly to the bottom line. How much is your operation worth per hour of production, when those hours can be saved by better methods? February 2016 | ASME Power Division Special Section

ASME Power Division: Plant Operations and Maintenance Committee

A Message from the Chair The ASME Power Division’s Plant Operations and Maintenance Committee is comprised of a dedicated group of industry professionals. This group volunteers their skills, knowledge, experience and time in pursuit of identifying and sharing industry “best practices” in the operation and maintenance of power and other energy conversion facilities. The committee is comprised of members throughout the industry, including facility owners, O&M service providers, engineer/architects, equipment manufacturers, insurance agencies, and specialty consultants. The purpose of the Plant O&M Committee is to provide industry guidance on the selection, performance, operation and maintenance of power generation equipment and systems. This is primarily accomplished through sponsoring technical papers and presentations at the annual ASME Power Conference. The next scheduled conference will be a joint Power & Energy conference held in Charlotte, N.C., June 26-30, 2016. Our committee is currently organizing a technical track at the 2016 ASME Power Conference. This is an exciting time as we discuss key issues impacting the operations and maintenance of power and other energy conversion facilities. Change is occurring rapidly in the power industry resulting from a myriad of environmental and reliability issues. These issues directly impact the operation and maintenance of power generation facilities. The aging workforce in our industry also creates challenges regarding effective knowledge transfer and attracting new employees into this industry. The ASME Power Division Plant O&M Committee strives to provide a forum for discussing these issues. If you are interested in joining us, we generally meet once each year at the ASME Power Conference and have periodic conference calls. The committee provides a great forum to network and discuss important industry topics. If you would like more information about the Plant O&M Committee or have interest in joining, please contact myself or visit our group page on ASME.org. Thanks. Brian J. Langel, PE Manager Production Engineering Omaha Public Power District blangel@oppd.com ENERGY-TECH.com

ASME FEATURE But better tools and new technology in the hands of an uneducated worker are of little practical advantage. Competence is the ability to successfully apply knowledge and to demonstrate oneâ&#x20AC;&#x2122;s capabilities by doing, not just knowing. Moreover, it implies performance to meet a generally accepted standard. Workers must be taught how to perform to the standards and how to self-inspect their work. It is the human factor that is most often missing in the safety-quality-schedule equation.

Appendix A overview ASME PCC-1-2013 Appendix A, shown in Figure 1, is the best and most complete reference for this topic. Readers are referred to this source document as the place to start any approach to the subject. The ASME training & development approach ASME Training and Development (T&D) in collaboration with an Advisory Board of Subject Matter Experts (SME) and Reviewing Organization established its own Qualifying Organization and began operation of the program as of Spring 2015. The current version of the program concentrates only on the Qualified Bolting Specialist (QBS) level, with the other two ratings to be addressed only after the QBS course has achieved sufficient acceptance and geographic coverage to be viable.

tighten bolted joints in an effective, efficient and safe manner. Through training and testing, successful candidates will understand and demonstrate the principles and practices of bolted joint assembly as outlined in ASME PCC-1 Appendix A. They will be able to meet its requirements, including the capability to: - Explain the objectives and methods involved in bolting assembly - Perform bolting tasks safely according to applicable standards and procedures - Identify and evaluate problems - Contribute to a safe work environment for bolting assembly activities

Online training Candidates will register directly with ASME Training and Development via their web site at www.asme.org. Among the advantages of an online curriculum are:

Eligibility and prerequisites Appendix A (Paragraph A-2-2) indicates that candidates for the QBS rating should have 6 months of active bolting experience verified by supervisory personnel in order to take full advantage of the instruction. Exceptions to the 6 month experience rule are allowed where the candidate comes properly recommended and properly motivated. In these cases the candidate can complete the experience requirement after the instruction is completed, but they will not be considered as fully qualified until that is done. Blended learning Because bolting is an inherently physical activity, it cannot be learned or mastered solely from a book or computer no matter how interactive or complete the curriculum. For the candidatesâ&#x20AC;&#x2122; own safety, as well as to verify that each individual completes their own work, they must be able to demonstrate their understanding and their capabilities in person. As previously mentioned, the hallmark of the ASME Training & Development QBS program is the combination of online technical instruction and testing, with hands-on practical demonstration and evaluation. The ASME Qualified Bolting Specialist Program is designed to train and evaluate a flange assemblerâ&#x20AC;&#x2122;s ability to inspect, assemble, disassemble and 26 ENERGY-TECH.com

Figure 1. This flowchart (Figure 1) outlines the procedural path both for potential qualifying organizations to follow to establish an acceptable program, as well as the steps for conducting training and evaluation and issuing a Qualified Bolting Specialist certificate.

ASME Power Division Special Section | February 2016

ASME FEATURE - Accessibility from anywhere with Internet access - Consistency of message not filtered by an instructor - Ability to update curriculum - Self-paced instruction progress - Unlimited enrollment not subject to class location and size The online training curriculum, Bolting Principles and Procedures, is delivered in four web-based interactive courses or parts with multiple-choice reviews and an online final examination for each part. In the online program, these will include: Part 1 – Principles of the Bolted Joint and ASME PCC-1 – introduces what is involved in bolting, why it’s important, common bolting principles, and the content and importance of the ASME PCC-1 guidelines. Modules include: - Why a course in bolting? - Principles of Bolted Joints - A review of PCC-1 Part 2 – Flanges, Fasteners and Gaskets – explains the relationship and importance of the three components – flanges, fasteners, and gaskets that make up a bolted, flanged connection. Modules include: - Introduction to flanges - Introduction to fasteners - Introduction to gaskets Part 3 – Putting It Together/Taking It Apart -- discusses bolting methodologies and procedures, including the role of torque in pressurized joints, methods to correctly tension and torque bolts, and how to identify and prevent corrosion and galling. Modules include: - Tightening with torque - Tension without torsion - Bolting patterns and sequences - What causes bolts to loosen and what to do about it - Dealing with corrosion Part 4 – Bolting Safety and Tool Handling – describes the importance of bolting safety, the need for planning and preparation in bolting practices, and the safe use and handling of bolting tools, including manual and powered tools and tensioners. Modules include: - Bolting safety - Making a bolting plan and using a checklist - Hydraulic torque tool operation - Pneumatic torque tool operation - Other bolting tools and accessories

Hands-on training Once the online portion of the course is completed, the candidate will register with one of many Authorized Training Providers (ATP) who will conduct the hands-on session. The intent is to engage as many high quality ATPs as possible in order to: - Keep the training as close as possible to the students - Avoid overnight stays with their inherent costs to both students and companies February 2016 | ASME Power Division Special Section

- Keep class size to no larger than 5 students per instructor (primarily for safety) - Maintain a consistent 8-hour evaluation program through use of a standard checklist format - Utilize experienced fitters and millwrights as credible practical instructors Tool Demonstration and Testing is delivered in a one-day, hands-on training session where the candidate will review, observe and demonstrate actual tool handling and safety principles. This training session can only be taken after successful completion of all four online courses. The training day will include the review and observation of actual tool handling and safety, the demonstration of tools with multimedia support, and participant demonstration of skills. Each student will have a checklist and the instructor will mark that he observed the student successfully complete or participate in each of the skills associated with each module. Modules include: - Safety and PPE review - Torque/Load measurement tools and techniques - Gasket identification and analysis - Manual torquing demonstration and horizontal flange assembly using manual torqueing - Hydraulic tool operation review - Hydraulic torquing demonstration and large vertical flange assembly using hydraulic torqueing tools - Pneumatic torque tool operation - Tensioner operation (hydraulic and mechanical - Summary and Q&A The completed checklist will be evidence that the skills were demonstrated and mastered by each student. No final examination will be given since the checklist serves as the pass/ fail document. The ATP will forward a copy of the completed checklist and its endorsement to ASME. Certificates with appropriate signatures will be distributed by ASME directly to the new Qualified Bolting Specialist.

Summary Some of the most numerous and critical joints in pressurized industrial systems are held together with bolts and sealed with gaskets. Bolted joints, unlike welded connections allow machinery and large process systems to be disassembled for maintenance and repair and then reassembled. While there has long been an accepted standard requiring welders to be trained and qualified, there has not, until recently, been a parallel program to train and qualify bolted joint assemblers in their equally important craft. A new ASME standard PCC-1-2013 Appendix A has been approved to permit and foster exactly that training. Although the standard allows for many organizations to offer courses which “comply” with the guidelines, ASME has produced a definitive blended learning program that accomplishes the goals of PCC-1 and gives industry the best accessibility, consistency and cost options. It is hoped that the program soon becomes a regular

ENERGY-TECH.com

ASME FEATURE part of maintenance training for bolted joint assemblers across the country and around the world.

References 1. ASME PCC-1-2013, “Guidelines for Pressure Boundary Bolted Flange Joint Assembly”, Appendix A, “Training and Qualification of Bolted Joint Assembly Personnel.” 2. ASME Guidelines for Development & Delivery of Certificate Programs, last updated March 2013. 3. Marsh, 2003, “The 100 Largest Losses, 1972-2001, Large Property Damage Losses in the Hydrocarbon-Chemical Industry”, Report by Marsh Risk Consulting Practice, 20th Edition, February 2003.

Jerry Waterland is vice president of VSP Technologies, where he leads the Sales and Engineering teams. He graduated from West Virginia University in 1983 with a degree in Mechanical and Aerospace Engineering, and spent the first 13 years of his career with W.L. Gore and Associates Inc.- Sealant Technologies Group. Applying engineering analysis and principles to the field of Fluid Sealing, Waterland is the author of numerous technical papers and holds 14 U.S. Patents for fluid sealing products and processes. He is currently a member of the ASME PCC-1 S/C Bolted Flange Assembly, Vice Chair of the ASME Pressure Vessels & Piping Division (PVP) Computer Technology & Bolted Joints technical committee, and serves on the ASME Training & Development Division’s Flange Assembly Qualification Certificate Course Advisory Board. You may contact him by emailing editorial@woodwardbizmedia.com.

Editor’s note: This paper, PWR2015-49032, was printed with permission from ASME and was edited from its original format.To purchase this paper in its original format or find more information, visit the ASME Digital Store at www.asme.org. David E. Lay, BA, MBA, is the director of Training for Hytorc. He has been involved in teaching both the theoretical and practical aspects of heavy industrial bolting since 1992. Lay is the author of the OSHA Training Institute course, “Safe Bolting: Principles and Practices” (OSHA Course #7110), and several multimedia courses that have been adopted as teaching standards for union apprentice programs in the millwright and pipefitter trades across North America. He is an affiliate member of ASME where he serves on the Post-Construction Standards Committee and the Bolted Flange Joint Subcommittee, which created the PCC-1-2013 “Guidelines for Pressure Vessel Boundary Bolted Flange Joint Assembly” document. He also is the principal author of the flange bolting sections in the current revisions of the American Water Works Association AWWA M-11 and C604 standards for steel pipe. You may contact him by emailing editorial@woodwardbizmedia.com. Michael Dodge joined ASME in 2010 and has more than 25 years of experience in all aspects of training and development. He currently serves as the manager for the development of training content for ASME. Prior to joining ASME, Dodge worked with financial training companies and engineering firms. His expertise covers the entire development process, including needs analysis, writing and editing, designing and developing training courses, managing the production of training programs, and producing and presenting training courses and seminars. Dodge also is experienced in the development and implementation of large-scale training programs from start to finish, especially in the use of interactive and Web-based technology to improve adult learning. He holds a Master’s degree form Emporia State University. You may contact him by emailing editorial@woodwardbizmedia.com.

28 ENERGY-TECH.com

ASME Power Division Special Section | February 2016

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29 26923

MACHINE DOCTOR

Catastrophic centrifugal compressor failure during shutdown By Patrick J. Smith, Energy-Tech contributor

In the November 2015 Energy-Tech article, “Catastrophic centrifugal compressor failure during start-up,” it states that “… preventing machinery failures requires a good machinery condition monitoring program, a good machinery protection system and good maintenance practices.” However, problems in centrifugal compressors can sometimes be difficult to detect and sudden, catastrophic failures can occur. Many of these failures take place during transient events. The purpose of this article is to present a case study where a centrifugal compressor was running well, but then failed suddenly during a controlled shutdown.

Introduction This case study pertains to an integrally geared centrifugal compressor driven by a 5,000 HP, 3,565 RPM induction. The gearbox consists of a bullgear and three rotors. Each rotor consists of a pinion with overhung open impellers mounted at each end. The compressor stage 1/2 rotor and stage 3/4 rotor are mounted on the gear case horizontal split line, while the stage 5/6 rotor is installed in a split line in the upper gear case cover. The gas seals at each stage consist of rotating laby teeth running against a Babbitt lined bushing. The oil seals at each stage consist of stationary laby teeth running against the shaft. The gearbox configuration for stages 1/2 and 3/4 is shown in Figure 1; the stage 5/6 rotor is omitted for clarity.

Figure 1.

30 ENERGY-TECH.com

The gearbox utilizes tilting pad journal bearings for all three pinions with a single non-contacting proximity type shaft vibration probe adjacent to each bearing. The pinions are fitted with thrust collars that transmit pinion axial thrust to the bullgear. The thrust bearings are on the bullgear rotor as shown in Figure 1. The bullgear journal bearings are a cylindrical sleeve type and the thrust bearings are a tapered land type. The compressor protection system includes high pinion vibration alarms and high high pinion vibration shutdowns. Although this compressor is packaged with the intercoolers on a common base, several coolers were removed after it was assembled at the compressor manufacturer. This was done for shipping purposes. The compressor was re-assembled in the field by a qualified mechanical contractor. The 1st, 2nd and 3rd stage intercoolers are fixed in position and Victaulic pipe couplings are used for the interstage piping connections. The 4th and 5th stage intercoolers are mounted on spring supports and the interstage piping is hard piped with flanged connections.

History After the compressor was commissioned, it was put into continuous service and ran for 2 years. During this period the compressor was shut down approximately 12 times for short plant outages. There were no mechanical problems with the compressor during this period. On the last shutdown, the operator was following the normal procedure to unload the compressor prior to stopping the machine. However, as the compressor was being unloaded, the discharge pressure began to rise and the distance to surge decreased to the point that the surge control system opened the recycle valve. Seconds later the machine tripped on high vibration and the compressor was heavily damaged. A careful review of the operating data revealed that after the recycle valve opened, the vibration on all 6 stages went into alarm simultaneously. It appeared that the 5th and 6th stage vibration increased faster than the other stages, followed quickly by stages 2, 3 and 4. The data did not show any evidence of a performance instability leading up to the failure. The compressor was disassembled and there was significant February 2016

MACHINE DOCTOR damage to rotating and stationary parts. A summary of the damage included: - Pinion 1 (Compressor stages 1 and 2) o Extensive gearing damage o Moderate impeller, bearing and seal damage - Pinion 2 (Compressor stages 3 and 4) o Extensive gearing damage o Extensive impeller, bearing and seal damage - Pinion 3 (Compressor stages 5 and 6) o Extensive gearing damage o Extensive impeller, bearing and seal damage - Bullgear o Extensive gearing damage o Bullgear bearings – Excessive thrust face Babbitt wear on the non-drive end bearing Figure 2 shows a damaged pinion where it can be seen that the shaft end that drives the impeller was snapped off. Figure 3 shows damage to the normally unloaded bullgear thrust bearing. This is discussed in more detail later in article.

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Root cause analysis (RCA) The following causes were investigated as part of the failure analysis: - Mechanical design - Progressive wear/damage - Surge - Operator error - Control system - Gearbox distortion - Reverse rotation Mechanical design The gear and bearing loads at the design conditions and over the full operating range were reviewed and were well within industry experience. Thus, it was concluded that excessive gear, bearing, thrust collar or shaft loads did not contribute to the failure. During the repair no changes were made to the compressor mechanical design. Progressive wear/damage Long-term operating trends showed no signs of progressive mechanical damage or wear. There were no detectable changes in long term vibration trends or thermodynamic performance. However, the bullgear thrust bearing damage was predominately on the non-drive end, which is opposite the calculated direction of thrust at the design operating conditions. Thus, it is likely this damage occurred during a transient event, such as a compressor shutdown, and not during normal steady state operation. Since there were limited shutdowns, this damage could have gone undetected until there were sufficient shutdowns that the damage reached a stage that finally allowed contact between rotating and stationary parts. The bullgear shaft is not fitted with a position probe and so it is not possible to determine exactly when the damage occurred.

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MACHINE DOCTOR consistent with many other similar machines in the industry in this type of service. In addition, the compressor was shutdown numerous times without any issues.

Gearbox distortion The millwrights that removed the compressor after the failure reported a difficult time removing some of the piping due to excessive misalignment. During reassembly at site after the failure, numerous interstage pipes had to be modified in order to correct this piping misalignment. A picture showing some of the gross piping misalignment is shown in Figure 4. It was concluded gearbox distortion resulting from excessive piping misalignment could have contributed to the failure by resulting in reduced impeller clearances and/or bearing and seal misalignment. Figure 3.

Surge The operating data immediately prior to the failure showed no evidence of operation in surge. The machine vibration levels and performance were stable and not erratic up to moment of failure. Thus, it was concluded that that surge did not contribute to the failure. Operator error There was no evidence of mis-operation. The compressor was not operated in surge or at overload condition. And although the recycle valve opened just prior to the trip, the control system performed as designed to prevent a surge. This machine had been through several full load trips previously in which the recycle valve opened automatically, but there were no mechanical issues following these incidents. Control system There was no evidence that the compressor controls did not perform as designed. The mechanical protection system was

Reverse rotation A review of the data at the time of the failure did not show any evidence of reverse rotation on the compressor shutdown. After the repair, the compressor went through extensive testing at site and following the first full load shutdown test it was observed that the compressor stopped rotating about 10 seconds after being tripped, and then spun backwards for about 1-1/2 minutes, reaching a reverse speed of about 1,000 RPM. This was seen by a GE-BN vibration analyzer that was being used for detailed vibration testing following the repair. See Figure 5. Operating in reverse is something that should be prevented due to potential for damage/wear from lubrication problems, possible over pressure of oil pump suction piping, damage to oil pump foot valves and possible damage to bearings. The bullgear tapered land thrust bearings in this machine are a unidirectional design and have significantly reduced load carrying capability when operating in the reverse direction. If the normally unloaded bullgear thrust bearing was damaged due to repeated reverse rotation incidents, this could have contributed to the compressor failure. On a compressor shutdown, the recycle valve opens to reduce the discharge pressure to prevent surge and reverse rotation. If the discharge pressure is not reduced quickly enough, the trapped gas can act like an act brake, stopping the compressor and then reverse flowing until the suction and discharge pressures equalize. High reverse flow through the compressor can cause the compressor to rotate in reverse and act like an expander. To prevent this from occurring, the recycle valve needs to be sized to handle the required flow, the recycle valve needs to open quickly, a check valve needs to be installed downstream of the compressor discharge and the discharge piping volume needs to be minimized. To address this, the recycle valve opening time was reduced as much as possible and a discharge dump valve was added. This valve opens on a compressor shutdown to vent high pressure discharge gas to atmosphere. RCA Conclusion It was concluded that the compressor failure was most likely a result of a sudden hard seal and/or impeller rub in the 5th

Figure 4.

32 ENERGY-TECH.com

February 2016

MACHINE DOCTOR

Figure 5.

stage followed by catastrophic secondary damage to stages 3, 4, and 6. All or some of the following issues most likely caused and/or contributed to the failure: - Reduced operating clearances due to excessive gear box distortion caused by excessive pipe strain. - Non-drive end bullgear thrust bearing wear/damage during repeated shutdown reverse rotation incidents. - Non-drive end bullgear thrust bearing wear due to gearbox distortion.

Corrective action The following correction action was implemented: - Ensured there was minimal gearbox distortion due to excessive piping misalignment. During re-assembly several pipes had to be modified to accomplish this. - Added a discharge dump valve that opens on a compressor shutdown to vent high pressure discharge gas to atmosphere. In addition, the recycle valve opening time on a machine trip was increased as much as possible. - Added a bullgear axial position probe for indication, alarm and shutdown protection. Conclusions The compressor has operated well since it was repaired and the corrective action was implemented. There have been no indications of any mechanical damage. The vibrations have remained low, the bullgear axial position has been stable, the seal leakage has been acceptable and there has been no change in the thermodynamic performance of the compressor. This is a well-designed compressor that was installed by a qualified mechanical contractor. Once the compressor was placed in continuous operation, it ran flawlessly for two years. The machinery protection system was similar to many other

machines and there were no indications of any mechanical problems. And yet, the machine suffered a sudden, catastrophic failure while being unloaded as part of the normal shutdown procedure. The causes of the high speed turbomachinery failures are not always obvious or conclusive. The available data, speed at which the failure takes place, the amount of secondary damage, and other factors make it difficult to be certain of the causes of the failure. In this case, it is believed that the failure was caused by excessive gearbox distortion due to piping misalignment and/or bullgear thrust bearing damage due to repeated reverse rotation incidents. The issue with the piping misalignment was only discovered after detailed interviews with the mechanics that removed the piping following the compressor failure. The issue with reverse rotation was only discovered when the vibration and speed trends were reviewed during detailed vibration testing that took place after the compressor repair. Compressor speed is not monitored in the control system and the control system vibration trends are not sensitive enough to easily observe the reverse rotation after a compressor trip. These two issues could have been easily missed had a thorough RCA not been performed. If the corrective action was not implemented, this machine would be at a higher risk for another failure. Any time there is a failure or significant mechanical issue with a piece of rotating machinery, an RCA should be performed.

References 1. Smith, Patrick J., “Catastrophic Centrifugal Failure During Start-up”, Energy-Tech magazine, November 2015.” Patrick J. Smith is lead machinery engineer at Air Products & Chemicals in Allentown, Pa., where he provides technical machinery support to the company’s operating air separation, hydrogen processing and cogeneration plants. You may contact him by emailing editorial@woodwardbizmedia.com

February 2016 ENERGY-TECH.com

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DHCP = $AFETY

for your GE Hydrogen-Cooled Generator ™

WHEN HYDROGEN PURITY DROPS, windage losses increase, operating costs increase – and then your plants lose revenue and profitability. Gas purity is also a critical life safety issue, making monitoring for potentially explosive levels essential. E/One’s Dual Hydrogen Control Panel (DHCP) was designed specifically for monitoring and controlling hydrogen purity in GE generators that utilize scavenging seal oil systems. The DHCP contains two independent analyzers that monitor hydrogen purity from both the turbine-end seal drain enlargement and the collector-end seal drain enlargement. Designed to be used in a hazardous location, the DHCP has the ability to automatically increase the amount of hydrogen gas bled from the generator. It’s also an easy drop-in replacement for your old hydrogen control cabinet. Featuring digital displays, warnings and alarms the DHCP works with all GE and non-GE control systems. DHCP = $AFETY, it’s just a little equation, but it delivers huge benefits. Visit www.eone.com/solutions today to find out more about increasing your plant’s safety and profitability.

Environment One Corporation www.eone.com/solutions A Precision Castparts Company

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