The Bulletin – February 1990

Journal of the Association for Petroleum and Explosives Administration

It's

Am ero n' s Dualoy"' 3000/L fib e rg lass pipin g is li ste d w ith Und e rwriters' Laboratorie s for u se in und e rgro und fuel-handling sys te m s . It h as a lso been tes t e d and acce pte d by th e London Fire and Civi l De fe n ce Authorit y

Th i m ea n s yo u h ave th e ass u rance th at o ur product h as b ee n tes te d und e r th e mo s t s tring e nt c on diti o n s a nd is ra te d for press ures a nd tem p era tures far in excess o f 1eg ul ar p e trol s tation require m e n ts.

Yo u ca n in s ta ll a Du a loy sys te m in ab out o n e h a lf th e tim e re quir·ed to put in s tee l. In fa c t , you ca n ta p e r th e e nd o f o ur pipe in less tim e t h an i t takes ju s t to put a s tee l p i pe in a p ip l' v is e

But h e re's the best part: you'll probabl y find the installed cos t of a Dualoy system to be less tha 11 f _ I · · Ot stee -:-as it r e quires no sulphate res1st111g concrete surround.

Ameron ha s a Dua loy system for eve r y und e rground fuel-h an dli nee d: wh e ther .it' s convention a i1 g s m g le-wa ll p1pmg or a co mpl ete secondary con tamrn e nt sys te m

For m ore inform a tion, wr it e Am e ro n Fib e rglass Pip e Di v is ion P.O. Box 6, 4190 CA Geldermals e n ' Th e Ne th e rland s or ca l l u s at ' 03455 73341

approved by petroleum licensing authorities and installs twice as fast as steel.

Dualoy 3000/L co ntainmen t systems are al so UL li sted for al c ohol based fuels as we ll as petrol

Intr oducing from

the new 61-SO Overfill Prevention Valve

Fea t u res :

T he OPW 61-SO overfill prevention valve is d esigned to be a simple, low cost solution to positive shut-off of product fill for underground storage tanks. The shut-off valve is an integral part of the 4" drop t ube used for submerged filling. No extensive or expensive excavation is required. The OPW 61-SO can easily be ret rofit into most existing locations. No special manholes are required Installing th e OPW 61-SO is as simple as changing drop tu bes.

Th e OPW 61-SO is a two-stage shut-off valve When liquid level rises to approximately 95% of tank capacity, the valve mechanism is released and the valve closes automatically with the flow This reduces t he flow rate to app roximately 5 gpm t hrough a bypass The operator may then stop t he filling p rocess, d isconnect and drain the delivery hose As long as the liquid level 95% of tank capacity t he valve close automatically each t ime delivery is attempted

If the storage tank is overfilled to an unsafe condit' b ion and the liquid rises to 98% of tank capacity t he bypass into No additional liquid will flow a resete Until t he level drop s below point.

* Simple, easy and quick Installation no excavation or special manholes required.

* Economical costs a fraction of expensive, complicated and difficult to install valves.

* Completely automatic operation no pre-checks to perform, no resets, no overrides to be broken or abused.

* Works at all flow rates operates directly from liquid level.

* Will accept a dipstick for gauging.

* Retrofits directly for existing tanks and 4• riser pipes.

* Automatic hose drain for operator convenience.

* LFCDA approved.

Materials:

Valve body: cast aluminium

Float: nitrile rubber, closed cell foam

Valve : aluminium Seals: viton

Upper & Lower Drop Tube: aluminium

Opinions expressed in this Journal are not necessarily the views of the Association

Talking Point

The subject of overfill prevention devices has thrown the Oil Industry into turmoil. While two of the major oil companies are committed to public safety (well done BP & MOBIL) others seem more reluctant. It seems that much of the argument within the Oil Companies is which Budget it comes out of, marketing or operations.

The Association had hoped to persuade the Oil Industry to follow the European examples where such devices are required. It has not given up this hope of persuasion but if progress is not made soon then the steps taken by CAMBRIDGESHIRE C.C. (see Notes and News) will be the likely course of all petroleum licensing authorities.

notes and news

Code of Practice

FOR THE DEVELOPMENT OF A RESPONSE PLAN FOR SERIOUS INCIDENTS INVOLVING PETROLEUM PRODUCT ROAD TANKERS

The volume of hazardous materials being transported in Great Britain has encouraged the road transport panel of the Institute of Petroleum to produce formal guidelines for a response plan for an emergency situation where a road tanker has been involved in a serious incident, possibly overturning and causing spillage of product which may damage or otherwise affect a third party, property or the general environment.

This code which deals in detail with the oil company's inhouse response to an incident also covers the roles of the police, fire brigade, water authority, ambulance service and vehicle recovery contractor, all of whom have been consulted during the preparation of the code.

'Code of Practice for the Development of a Response Plan for Serious Incidents Involving Petroleum Product Road Tankers' is available from:

The Library

The Institute of Petroleum 61 New Cavendish Street London WlM8AR

Tel: 01-636 1004. Telex: 264380. Fax: 01-255 1472

Price: UK: fl0.00 Overseas: f 13.00

RE: PM TRAINING CENTRE, FIRETHORNE

PM Technical Services have recently joined with F1retho t·· · 1. rne. ire consultants and fire training spec1a 1sts. to provide fire precaution and fire fightina cour.,es for the staff of PM Services Limited. These courseshave been held at the residential t · · h t. II ram1ng centre. Haygarth House. with t e u <tpproval of M , Th r C 1 Cooper. Health and Safety Manager. e course · · coverin · consists o1 lectures and demonstrations g the characte · t. 1· ·· ·· · d ha1.arcl ns 1cs o tire. tire precautions an ous substances Obviously. becau. . . Services L · se of the type o1 work earned out hy PM · ,1rn1ted the , .. .· fires in Ii ·d · courses have considered the e1 tech o1 qu1 luels. A . · ol the use t· f" . lllaJ.or pan ot the course has consisted · 0 lfe ex 1 , · I n.:quired to nguis iers. All the course members are extmgu1sh b · t'Xtinuuishe S · urnmg petrol usmg all types of tire 1::- rs. · uccessfu I 1 · 1/w aw·ircl < 1 , · · comp ct1on of the course results 111 ' > d cen1f1cate

While aimed at the st· f:1 · <1 ol PM Services Ltd, the course can lw prov 1ded tor othe.1 personnel engaged in the petroleum 111du\IJ'\ It <myrme is· t'· · · · · · · · .· 111 e1estecl m prov1d1ng this type ol 1!;1111111µ Im 1lw1r stall. please contact P. Keith at Haygarth I lri11»r· I t•/t'plHHIL' 0777 708681.

BENNETT BECK OBTAIN FIRST PETROL PUMP APPROVAL UNDER BS 7117

Bennett Beck the petrol pump manufacturer announced in November 1989 that they were the first manufacturer to receive approval of a petrol pump under the new British Standard BS 7117 Part 1. A certificate of assurance BK 89 Y 9395 is being issued by BASEEFA for the pump.

The approval under the new standard confirm that the new pump conforms with not only electrical safety, but all other safety features encompassed in the BS 7117 document.

OVERFILL PREVENTION DEVICES TO BE REQUIRED

After reviewing their constructional requirements for petrol filling stations and in the light of recent incidents Cambridgeshire County Council Trading Standards Department, as from 1 January 1990, will require suitable overfilling prevention devices to be fitted to all new underground storage tanks which have off-set fills. A number of other petroleum licensing authorities are likely to follow.

COMMUNICATIONS

Following a fire and fatalities at a Workshop in a Retail filling station, a major Petrol company has carried out internal investigations which have revealed flaws in the flow of information between the Retailer, the Licensing Authority and the Company.

These centre around the issue of a Petroleum Licence by the L.A. to the Licensee, the contents of which bear upon the Company's responsibilities to equip and maintain the premises, but which were not communicated to the Company by the Licensee.

It was found, as a consequence, that the Company staff responsible for the site were not aware that the Licence embraced the whole site, including the Workshop, and that modifications to the heating carried out by the Company, violated Licence Conditions.

A procedure now in place will greatly assist in avoiding this sort of ignorance. All retailers operating sites owned by the Company will provide a copy of the current Licence to the Company. which will be held on site records. Staff will have the opportunity to refer to these records whenever works are planned for any of the sites. Such violations will not be as likely to occur in future.

Aclclitionally. the Company has a suggestion to bring to all L.As. to further reinforce the education process.

It is recognised that. following the launch of the new f p , ·t. 1 A n1·1y well revise their Licence and Stand<11 d o rac ice. ,. s. , C I p hi .. ty t'<ii· e·ich L A Conditions. whether. Ill one 1t1ons. ll JCI ,. ' ' 11 b ·ven throuoh the pages ol concert or in sequence. cou l e g1 "". the APEA Bulletin. thus reaching a wide audience of other L.As, Retailer groups and all Petrol companies.

Company staff. many of who are memhers of APEA. could share knowledge thus gained with their peers. which. togt'lher with their extra diligence in referring to site records \vould go a long way to avoiding recurrence of such a lra)ledy.

Prosecutions

MAJOR PETROL RETAILING COMPANY FINED AFTER ALLOWING AN UNTRAINED EMPLOYEE TO SUPERVISE PETROL DELIVERY

On 19 October 1989 at Brentford Magistrates' Court in West London, Star Service Stations Ltd were prosecuted by the London Fire and Civil Defence Authority for infringements which occurred at the Star-Hogarth Service Station in Chiswick as follows:-

(i) (ii)

condition 13 of the petroleum licence, which requires that the licensee company "brings to the notice of all concerned the provisions of The Dangerous Substances (Conveyance by Road in Road Tankers and Tank Containers) Regulations 1981", and

paragraph 5 of Part I of Schedule 4 of The Dangerous Substances (Conveyance by Road in Road Tankers and Tank Containers) Regulations 1981, which requires that "some competent person who is not the driver of, or any other person employed to be in attendance on, the vehicle from which the delivery is to be made, is in charge of the storage tank for the purpose of the delivery".

On 7 October 1988 a spillage of petrol occured when an underground tank became overfilled. Subsequent investigation by the Petroleum Officer revealed that an unsigned delivery certificate had been left earlier in the day for completion by the cashier when the delivery arrived later, in anticipation that sufficient fuel would have been sold to accommodate the proposed delivery. Upon interviewing the cashier it was apparent that he had no knowledge of the procedures relating to the correct completing of the delivery certificate, or of the need to ascertain the contents of the tank immediately before delivery commenced. When the road tanker arrived, he simply signed the certificate and allowed the delivery to proceed. It was subsequently admitted by the company that the cashier had not been correctly trained and not competent to oversee the safe delivery of petroleum spmt.

A plea of guilty was entered on both counts and Mr S McDoom, presenting the case for the London Fire and Civil Defence Authority, explained the serious circumstances of the case and stated to the court the potential consequences should spilled petroleum spirit be ignited.

The Magistrates imposed fines totally £2000.00 (£I 000.00 for each offence) and awarded full costs of £387.00.

PETROLEUM PROSECUTIONS IN DORSET

Positive action by Dorset Trading Standards has resulted in local Magistrates· Courts imposing stiff penalties on businesses who have failed to comply with Petroleum Legislation.

One case concerned the failure of a company to render safe storage tanks. Auto Maintenance (Wareham) Ltd failed to ensure that underground storage tanks had been made safe on a site they were about to redevelop. 3 summonses alleged:-

(i) failure to take such steps to render storage tanks safe as advised by the enforcement officer prior to the expiry of the storage licence.

(ii) failure to give notice in writing of intention to discontinue storage as required under licence conditions and

(iii) the keeping of at least 47 gallons of petrol after the licence had expired.

Fines totally £600 and costs of£148 were imposed.

Two other cases worthy of note concern the storage of Petroleum Mixtures. Both cases arose from comprehensive routine inspection of a traders premises for Trading Standards matters. In the first case Woodhaven Products Ltd of Christchurch were found to be storing petroleum mixtures in excess of the amount permitted by the licence, to the tune of 1400% and also in unsafe conditions such as the staff toilet and tea room. The company was fined £ 1OOO and costs of £431.65 were awarded.

In the last case, petroleum products were found on unlicenced premises, stored in unsatisfactory conditions. The company, Kitchenalia of Wimborne, were fined £1000 and £ 158 costs awarded.

PROSECUTION ON ROUTINE INSPECTION

The following Prosecution was held at Birmingham . F ·d JO November 1989. Magistrates Court on n ay

. t the owner of Northfield Service Station The case agams . d. · f . d f"'ences in relation to his con ltlons o who had comm1tte o 1 ' licence.

. . . h ere bought, but three were mutually Ten 1111tial c arges w · h . d f dant agreeing to plead guilty to t e dropped with the e en ' other seven.

'!l1d the following fines levied against The case was proven ' the defendant by the magistrates.

the cap to a fuel pipe. Fine £ 1,000 Failmg to secure

· h· mber full of mud and water. Fine £500 2 Inspection c a

· chamber contained water and quantity of 3 lnspect1on ' petrol. Fine £500

4 Screed at base of pump defective. Fine £500

5 Delivery hose to pump one in dangerous condition. Fine £500

6 Delivery hose in pump three in dangerous condition. Fine £I ,OOO

7 No provision of dry sand. Fine £200

Costs of£75 was awarded bringing the total fine to £4.250

Letters to Editor

Dear Editor,

I wish to outline an incident regarding a suspect leak at a Petroleum Filling Station in my licensing area, which transpired into a somewhat unique search for its source.

Initially Officers attended the premises following a report of petroleum spirit being present in a resident's garden and reported smells of petrol in drains across a nearby housing estate.

The petroleum installation, which was new throughout, was pressure tested and found to be satisfactory, but still the petrol remained in locations off site.

. A 5 _metre deep concrete shaft was sunk near to the mstallat1on to create a collecting point for the spirit and the rec?very rate averaged 300 litres per week during some penods.

Independent laboratory tests indicated recent product which was contaminated with 7% bituminous contaminant.

Further pressure tests and extensive colour dye testing failed to locate the source of the leak.

. The search began for an alternative source and surrounding installations within a 1 mile radius were checked. Consideration was given to a groundwater problem as a result of possible contamination from any previous leakage from the old installation. This theory was later disregarded.

Despite numerous high and low gas pressure tests and hydrostatic pressure test, using ultra violet colour dyed water, the source of the leak eluded all concerned. No stock losses could be observed.

The tanks were eventually emptied of water and some vacuum tests were carried out which again proved negative. A total_ of 18,600 litres of petroleum spirit had been recovered. The mvestigation involved enquiries to 24 other parties, many whom visited the site only to be left baffled by the phenomena". Every conceivable avenue was explored, ranging from the logical to the ridiculous, but no leak was ever found.

The site has again been redeveloped and the new installation has been running satisfactorily for several months. The previous installation, being only three years old, was written off by the oil company concerned and the tanks infilled with concrete slurry.

Yours faithfully, K. W. Jones Chief Fire Officer, Gwent Fire Brigade

Dear Editor,

I read with interest the article in the November 1989 issue of "The Bulletin" regarding internal fill pipes.

Our company manufactures a wide range of Forecourt Equipment including fillpipes. We are able to offer both types of pipe, the older style fitted from beneath requiring removal of the manlid. However we do manufacture a pipe fitted externally. This pipe is fitted with a mild steel head threaded bsp taper both male and female, to enable it to be fitted directly into the tank 4i socket (3i also available). The head is finished by a plating process BS4921 class 1 sheradizing, to give good resistance to the damp or wetter conditions. The tube is aluminium grade HE9TF, 16 s.w. gauge thick. The head is fixed by a double swaging and rivets, the middle swage having a petrol resistant seal, to ensure a full liquid seal.

I have enclosed a drawing which may be of some use to you. The tubes are available from stockists or direct from the manufacturer.

Yours faithfully Peter Godfrey Member Apea

The Wright Engineering Company Masons Road, Stratford-upon-Avon, CV37 9JA Telephone 0789-292939

TUBE

PETROL AND OIL RESISTANT SEAL

Sec o ndary Containment -A Way Forward

BY DENNIS W. O'BRIEN, VICE PRESIDENT M.P.C. CONTAINMENT SYSTEMS LTD, CHICAGO

WHY SECONDARY CONTAINMENT?

.secondary containment is being used in North America pnmanly protect the drinking water of the people. In the U .S.A ., 50 7o of the populati·o . f d n get s its water rorn aroun water. Regulations in the state ofC i·f · · f0T f h N a 1 orma , 111 areas o exas , 0 t e ew England sites, as well as three counties in Flonda mandate s econda . 1 ry contamrnent for all underground gaso me storage tanks In C d h . · ana a t e prov f N Brunswick, Nova Scotia and p . Ed mces o ew ·t· nnce ward Island require it 111 sens1 1ve areas. There are th . . . countie s which al so man ° er c'.tie s, provmces and date second at Y contamment. The reason for the re gulation in these . d d . . . m 1v1 ual JUn sd1ct1on s 1s the se.n s 1t1v1ty of the g round wate r s upply.

It 1s mandated m all of the U .t d S n1 e tate s for li s te d ha zardou s chemical and haz a rdou s wa s te s to. k TI · tag e tan s 11 s is required for bo th the tank and the pipin g

In the citi es of Toronto and Montre al · c d · · 111 ana a , 1t 1s re quired for und e rground tank s in c lo se proximity to th e s ubway tunn e l: . In no n mandat e d a re a s sec ondary co ntamm e nt 1s trequ e ntl y use d as a m ea n s to isolate a nd prot e ct th e o w ne r o f th e ta nk s from th e pot e nti a l for ve ry c o stly liti g ati o n in th e eve nt of a lea k. Th e U nit e d Sta tes h as t wo third s of th e wo rld 's lawye rs a nd as a res ult it is a ve ry liti g io us e nv iro nm e nt .

As a n example , one of th e ea rly und e rg round ta nk le a ks h I t cl tlie requirement for second a ry contamment w 1c 1 promp e · c l'f · · vol\' ecl a waste solvent tank. This tank of m a 1 om1a 111 · I 5000 aallons lo s t som e wh e re be twe e n 50 ,000 approxunate y o cl 60 OOO lions of product into th e g round. It wa s 111 a an , ga I · hi a bl e soil c ondition a nd rapid s pre ad of th e plume 11g y pem1e _ d The Spl.11 w as not di scovere d unttl e xc av a tion 1or occuITe ' b ·id· an s 1011 found pre se nc e o f th e solv e nt. Th e co s t of u1 m g e xp , I e l 1s no w in e xc e ss of $ 50 milli o n Th e curre nt t 1e recov l ·t e iidin a ha ve exc e e de d o ne btlli o n dollar s aw s u1 s p o

WHAT IS THE PR O B LE M?

Prim a ril y it is poo r ta nk m a na ge m e nt. Wh e n th e pri ce o f fu e l wa s lo w, o n th e o rd e r o f 15 ce nt s to 20 ce nt s pe r ga ll o n prior to ta xes, th e eco no mi c loss was sm a ll eve n if I 00 o r 20 0 ga ll o ns a wee k w as mi ss in g. Up until rece ntl y it was no t easy to ca lc ulat e th e losses fr o m lea k age Th e dip sti c k p rov ides a aoo d m eas ure o f th e re la ti ve ta n k leve l. but d oes no t a ll ow fo r b acc ura te co m pe nsa ti o n fo r minut e losses escap in g th e ta nk S m a ll leaks a re di ff ic ult to find. Eve n w ith tank ti g htn ess test in g. it is s till no t ce rt a in th a t s m a ll leaks w ill be fo un d.

Underliner containing 5-20,000 g allon , 3-12 ,000 g allon and 1-4 ,000 g allon tanks Monitor w ells ar e in s ide the lin e r.

The U.S. EPA at their facility in Edison , New Jersey tested most of the tank gauges available on the marketplace and their report indicates that these devices are only accurate down to about .1 gallon per hour or equivalently an undetected loss of 2.4 gallons per day.

There still is a problem with installation. The U.S. EPA indicates that 25% of all leaks occur within the first two years. This indicates that even though there is a heightened awareness of the importance of proper installation to prevent leakage, sites are still being put together with faulty products and/or workmanship.

The sources of product entry to the ground are many These are I) the tanks, 2) the tank bung, 3) the piping, 4) the dispenser area, 5) the turbine pump and 6) delivery. The way each one of these product entry points is being dealt with is quite varied.

Leaks from tanks are being handled by using better tanks , electronic tank gauging or, at minimum, better inventory control. In some cases electronic tank gauging linked to remote management locations The purpose of all this is to keep track of the product so that a leak is noticed immediately.

Product releases out of the tank bung and also the vent lines, caused by overfilling , are being handled by the use of larger tanks This helps prevent the overfilling of the tank because it reduces the criticalnes s of the delivery timing In addition , overfill restrictors and electronic warning systems are being employed to prevent and/or warn the driver from overfilling the tank

In the piping area line leak detectors are being placed to monitor the condition of the product line s during delivery to alann and/or res trict th e flow when the leak is detected.

Under the di s pen ser, leak s from meter change s, filter change s and purging are being contained. Containment pans are used which trap the liquid and allow it to be phy s ically removed prior to entering the a round. When the state of California initially passed thei1':' re g ulations they allowed pre ss ure shutdown s in lieu of se condary containment. Howev e r, three ye ars after the enactment of this they re scmded the use of press ure shutdown s The reason s for this were lack of reliability , Jack of preci s ion and no ass urance th at they _were be ing checked for proper operation. At thi s pomt ,_California requires that the product line s be seco ndarily cont a mecl.

Trench liner in place at a fuel island. Piping is in place. Bolted ring is for under dispenser containment pan.

Trench liner in pla c e prior to piping. Yellow is the transverse z 1ppers jo inin g th e s trai g ht se c/ions lo turn component s

l

Driver training is being upgraded to prevent drivers from overfilling the tanks. Containment boxes are mandated in the U.S.A at the fill pipe to contain the product that would be left in the hose in the case of an overfill. Previously this product drained out onto the forecourt and worked its way into the ground .

WHAT IS SECONDARY CONTAINMENT?

Secondary containment is a method that provides complete containment of any leaks from the primary vessel. It should be constructed of a product which is compatible, as well as very impermeable, to the product stored. Compatability means that the secondary container is uneffected by the stored product. The contact of the primary product does not change the physical properties of the secondary containment material. Permeability is the rate at which the product will move through the secondary containment.

Secondary containment is not considered to be concrete vaults. Concrete vaults will crack due to natural curing and/or settling It is not clay liners. The U.S. EPA has banned clay liners from hazardous landfills and has also banned clay liners for secondary containment of underground storage tanks.

A secondary containment system is composed of three distinct features. One , it must contain the product from the leak in the primary container. Two, the secondary containment system must be monitored so that any leaks can be detected. The system should have a means to locate the source of leak. Three , the containment system must have a method to recover the product , restore the monitoring system to its original operating state and to continue operation. Failure to have these three items does not constitute true secondary containment. One of the most important things to consider is that the secondary containment system addresses all pos sible entry points into the ground. This is to prevent disruption of the facility when product enters the ground from one of the unprotected areas. This can be from on-site as well as s ite contamination migrating to the site monitors and setting off the alam1 This is particul arly true in a situation of

service stations. The source of the contamination may be from a competitor on an adjacent corner or up the street. Also , prior contamination may move back into the site during changes in the ground water table level.

The forms that secondary containment have taken are numerous. The excavation liners were the first form of secondary containment. The liners and the materials were developed for hazardous waste impoundments and landfills. These are chemically very sophisticated products and by selecting the proper product can be matched to any product that is needed to be secondarily contained They offer high strength plus flexibility to deal with surface loads and underground movement. Double wall tanks in both steel and fiberglass provide a second layer around the primary tank.

Spill collars are placed around the top s of the tank s to eliminate bung opening leakage as well as surface overfills from entering the ground. Double wall pipe provides secondary containment for the pipe using products both identical to the primary product as well as products different from the primary containment. Compatability must be closely checked if the secondary material is different from the primary.

In summary , there is a long history of the operation of a wide variety of fueling systems which were poorly managed. There is contamination at almost every site where fuel has been dispensed. Secondary containment is th e way forward to be sure that the problems of construction, manufacturing and installation are contained within the system that prevents the entry of the product into th e ground Secondary containm ent can be the way to isolate previous and future spill s from offsite locations from causing problem s on the new facility Full secondary containment in a litigation rich environment such as the United St ates provides a full measure of protection. The use of secondary containment will prevent both the releas e of the product into the environment as well as avoiding the costly litigation if the product migrates off site _Secondm y containment can be viewed as the in s urance pohcy that if a leak occurs it will not cause a major problem.

An Understanding of Composite Access Co

BY MIKE JENNINGS

In 198 5 Fibresec Limi ted introdu ced the first compos ite access c o v e r c apable o f withstanding the wheel lo adin g of heavy good s vehicles Th es e covers had exc eptional stren g th combined with lo w weight w hich m ade them ideal for application s o n the garage forecourt Th e id e a, of wh at m a ny people rega rded as a pl as tic manhol e cov e r , rai sed many eyebrow s and v ariou s comments of di sbeli ef, but tod ay the se composite covers have beco me the accepted standard a nd in exce ss of 20,000 are no w in use. Althou g h the se covers have g ained ac ce ptance man y en g ineers will h av e onl y a minimum knowled ge of compos ites a nd there e x ists nothing in the way of standard s to which th e en g ineer c a n re fer for guidance. This article therefore trie s to bridge thi s gap by providing a short ex c urs ion into the w o rld of compo s ites and pro vid e the bas ic d a ta for a standa rd which c an be applied by th e e ngin ee r.

Compos ites make u se of the enorm o us strength that very thin fibr es o f material s lik e class , carbon , boron and kevlar posses s . B y producin g a structure of the se fibre s and th e n bonding the m togeth e r w ih a re s in , a reaso nable propo rtion of the fibre stre ng th can be utili sed in th e product. The importa nt factor s w hi c h influence how s ucce ss ful the fibre stre ngth is utili s ed a re the type o f fibr e e mployed , the density of fibr e , how strai g ht it is within th e structure a nd finally th e res in sys te m e mpl oyed.

In a s tru c ture lik e a n access c o ver it is prim a ril y the fibr es w hich de te rmin e its stre n g th and th e m o re fibre s th at ca n be pac ke d int o a giv e n vo lume , th e g reate r the stre ng th Naturall y th e re ha s to be so me space fo r res in and as a g uid e to hi g h s tre ng th co mpo s ite w ill c onta in a t leas t 55 % by we ig ht of fibre. T o be e ffec ti ve th e fibr es sho uld be co ntinuou s and not c hopp e d up into s hort fibr es Man y fibre reinforc e d pl as ti cs cont a in ve ry short fibres a nd the se are of o nly limited va lu e in increas in g s tre ng th. Th e o th e r main p o int a bout fibr es is that th ey sho uld be kept as s tra ig ht as pos s ibl e. A fibr e th at is c rimp e d w ill be ha ve lik e a s prin g and wa nt to strai g hte n und e r load. Thi s imp a rt s additi o n a l stresses w ithin th e stru c ture thu s wea ke nin g th e compos ite

T od ay th e re a re a va ri e ty o f res in s av ailabl e s uc h as po lyes te r, e pox i, m o d a r a nd ph e no li c Th ey a re s uppli e d in a va ri e ty of g rades a nd a numb er are s uit a bl e for access co ve rs Th e res in ty pe has so m e influ e nce o n s tre ng th but is large ly re s po ns ibl e fo r the c he mi ca l re s is tan ce properti es a nd th e imp o rt a nt po in t is th at it mu st w ith s ta nd th e co nd iti o ns d isc ussed late r.

Le t us no w c o ns id e r the facto rs w hi c h mi g ht prov id e th e ba s is for a sta nd a rd A se ns ib le startin g po int is to exa min e th e ex is t in g Bri t is h S ta nda rd , w hi c h fo r m a nh o le cove rs is B S49 7 , a nd es tab li s h w hat is re le va nt. T hi s S tand a rd grades cove rs a nd t hese c lass ifi ca t io ns a re re leva nt , fo r a fo reco urt a C la ss B cove r be in g a ppro pri a te Ass oc ia ted w ith the c lass i f ica 1i o n load require me nt s a re s pec ifie d tog e th e r w ith a m e t h od 0 1· a pp ly ing th e lo ad Fo r ex amp le a Cla ss B co ve r mu s t he c a p a b le o f c a rry ing a 150 K N ( I S to n f) load w it ho ut c a u s in g pe rm a ne nt d e fo rmat io n T h is is accep tab le fo r a d uc til e iron c ove r bu t no t fo r a compos ite cover W hy? lh e fa 1i g ue prop e rt ies o f c ompos it es a re d iffe re nt frn!ll and u 1.st iron P ut s imp ly a compos it e m ust be m uc h

st ro nge r than stee l if it is to with sta nd be in g loade d a large number of tim es Covers on forec ourts can be re pe atedly loa de d with S to n as a direct res ult of a HGV p ass ing over th e m a nd in som e cases w here ve hicl es a re m o vin g a t spee d , th e re w ill be a n additional d yna mi c load. Ex pe ri e nce has show n th at for a co mpo s ite cove r to w ith sta nd thi s type of application it mu st ha ve a minimum failure lo ad o f 250 KN (25 ton f). As a further ch eck o n a comp os ite covers pe rform ance it sho uld be subj ecte d to a fati g ue tes t w hich w ill e nsure there a re no inh e rent wea kne sse s in th e structure des ig n . Suc h a tes t wo uld con s ist of appl y in g a load of 50 KN (5 to n f) in acco rd ance with BS:497 for 60 ,000 c yc les On co m p letion of th e tes t there should be no evid e nce o f any form of fa ilure.

Pl as tic s and glass fibre s a re effec ti ve in s ul a to rs a nd th e res in ca n be s ubj e c t to stati c e lec tri c it y probl e m s. Th e s urface res isti vit y o f a typi ca l res in is I x 1O13 o hm s a nd if th e re is a so urce which ca n pro vide a c ha rge, peopl e and ve hi c les ca n prov ide that so urce , th e n th e surface o f a co ve r c a n m a int a in a ve ry hi g h ch arge . Thi s is a ve ry d a nge rou s s itu a ti o n as a s pa rk co ul d be ge nera te d ca pabl e of ig ni t in g pe t ro l. He nce a ll co mp os it e cove rs mu st in c lu de in t he ir des ig n a mec ha ni sm fo r d iss ipatin g a po te ntial c ha rge. Fo r thi s to be e ffec tiv e th e surfa ce res ist ivit y has to be re du ced a nd mu st no t be g rea te r th a n I x I 09 o hm s. A furt he r so urce o f spa rks is th e ke y hou s in g whi c h w ill no rm a ll y be mad e o f me ta l. as a se para te part , bec a use of its co m p lex it y T he s impl e a nswe r he re is to e ns ure ii- is m ad e of a no n spa rk ing a ll oy

The quality of a product is very often determined by the process used in its manufacture and this is very much the case with composites. Fibresec employ an advanced process for the production of the fibre structure and injection of the resin. This results in a single moulded structure of aircraft quality. The type of processes to avoid are those which use short fibre composites such as SMG (Sheet moulding compound) and particularly hand lay-up methods. This latter method produces laminates of low fibre content, they tend to have air voids in the structure and require that several parts are bonded together to make a cover, thus introducing the weakness of a bond.

The last point we shall consider in this short article is the question of weight. The reason for using a composite cover is its light weight. So what is light, well a 600 x 600mm cover should not exceed 22 Kg and still provide the strength values previously discussed. If the cover weighs more then you do not see the benefit and the composite design is below standard because excess material had to be employed in its structure. So a covers weight provides an easy assessment of the products quality as does the manufacturing process used in its production.

To conclude this brief introduction into composite access covers. If you specify composite access covers for a forecourt situation insist that they meet the following minimum standard.

Static Load :

Fatigue Test :

Surface Resistivity : Chemical Resistance :

minimum load at failure 250 KN (25 ton f)

A load of 50 KN (5 ton f) applied for 60,000 cycles to be less than I x I09 ohms resistant to immersion in petrol and diesel fuel

the resin system to be approved by Lloyd's Register of Shipping for use in craft to be less than 22 Kg for 600 x 600mm cover

Continuous Site Pollution Monitoring

THE USE OF DYNAMIC FUEL STOCK MONITORING TO PROVIDE ENVIRONMENTAL PROTECTION SYSTEMS

1. Introduction

The role of tank gauging in the UK has traditionally been limited to that of an automated dip-stick. In some cases the tank gauge is employed purely for convenience. However, generally the tank gauge is there either to assist where an off-set fill arrangement precludes tank dipping or where other management devices allow for the input of real stock level data.

In other countries the tank gauge has been allowed to play the additional role of environment protection monitor. Lateral software development has shown that this approach is also suitable for the UK.

The tank gauge is set to play a major role in the future safe management of petroleum stock holdings.

2. Development of Tank Gauges for Leak Detection

The USA is the prime example of a market where the tank gauge has been adopted for environmental protection.

In the mid I970's the environmental lobby in the USA began to gather momentum after several instances of contaminated groundwater. It was particularly vocal in Southern California where drinking water is taken from groundwater supplies.

With literally millions of often ageing, poorly installed and poorly monitored tanks, a major problem was emerging.

Veeder-Root had a strong presence in California and set-out to react to the problems that customers were facing.

A segmented capacitance type probe was developed for monitoring the fuel in the tank. The TLS 250 console was designed to take the probe data and carry out passive leak detection and general inventory management functions.

By I984. a tank gauge developed specifically for leak detection was available to the market and by 1988, the Environmental Protection Agency <EPA) was nnplementing legislation requiring tank monitoring.

3. EPA Regulations & Veeder-Root Performance

The EPA has established a requirement that tanks should he regularly tested to a static tolerance of 0.2 gal Ions per hour. Several independent trials have established !hat the TLS 2.'iO is able to test to this requirement.

This approval and rhe general strategy has given the II S 2.'il I <ilmosl X<Vlr of all new tank gauge business in i/JC I SA There are approximately 30,000 TLS 2.'iO , ·,ft'.llh 1mtalled.

4. Leak Detection UK Requirements

The UK does not have in place, the level of legislation enjoyed by US safety agencies. In addition, the UK has different needs. Many UK retail sites work too many hours to make a 5 hour static test practical, and experience indicates that leaking lines are a greater problem than leaking tanks.

To encourage the deployment of environmental protection systems the Petroleum Officer requires to find some common ground between his needs and the needs of the petroleum retailer.

The retailer will be looking for incorrect deliveries, inaccurate dispensers, fraud and theft whereas the PO is concerned about line leaks, tank leaks and overfilling spillage. The interface between the commercial and environment positions is the cost to the retailer should the PO's concerns be borne out. This is too late to find common ground.

5. Management Reconciliation/Safety Reconciliation

Common ground can more easily be found by looking at stock reconciliation techniques.

Most site control systems are capable of carrying out a stock Management Reconciliation. This is the measure of the variance between what has been booked into the system as deliveries and what has been sold by the system. Such an analysis is greatly enhanced by the comparison of the declining bookstock with the contents of the tanks as indicated by the tank gauge (fig. I).

On the other hand, what is required for Safety Reconciliation is a measure of the variance between what is pumped off-site and what the tank gauge says was removed from storage (fig. 2).

Both types of reconciliation benefit from employing a tank gauge.

6. Safety Reconciler Which Serves a Management Reconcilor

Based upon the proven technology of the TLS 250, Veeder-Root have developed a system to carry out safety monitoring duties whilst performing as a normal fullfeatured tank gauge.

Figure 3 shows the operating environment of the new TLS 200R console. It receives tank data from a standard Veeder-Root probe in each tank. For presentation of tank volumes and for input to the Management Reconciliation it communicates with a site controller as normal. This is shown as the inner loop in the diagram.

For Safety Reconciliation, the site controller advises the TLS 200R of the volumes pumped off-site as seen hy the pumps over the previous hour. The TLS 200R checks these values against its own calculation of the volumes removed from storage and establishes the hourly variance.

The trend of these variances is checked against 2 tolerance levels. warning and alarm. When either tolerance is breached. action is taken according to a code of practice

Presentation by A F Chandler of Veeder-Root Ltd to the APEA Seminar at Dunstable 3 October 1989.

FUEL IN FUEL OUT

8. Code of Practice

Further discussions with Petroleum Officers have established a proposed Code of Practice for Safety Reconciliation.

A summary of this Code of Practice is as follows:

1. Check tanks and lines for leaks and pumps for measure prior to installation.

ii. Retain daily print-out for examination by PO.

iii. In the event of a reconciliation warning notify the PO and company auditors allow further 48 hours to confirm alarm status check meters on pumps connected to tank call maintenance engineer for site check.

iv. In the event of a reconciliation alarm: emergency call to PO and maintenance engineer if line leak or pump off measure rectify immediately if tank leak indicated empty tank and pressure test

if false alarm, notify PO in writing within 48 hours.

7. Proposed Tolerances

In discussion with both Petroleum Officers and major oil company users, acceptable tolerance levels have been drafted for safety reconciliation of petrol movements. (These may be relaxed for diesel).

To provide an indication of poor product reconciliation, a warning will be produced at ± 3 litres/ hour running variance.

When the variance exceeds ± 4 litres/hour the alann will be triggered for unacceptable safety reconciliation.

Figure 4 shows a typical plot of genuine variances for one tank and its associated pumps. The data was gathered over approximately a 9 month period on a UK trial site.

Fixed tolerances were selected in preference to percentage tolerances as this approach allows monitoring of both static and dynamic situations.

SAFETY RECONCILIATION

FUEL IN FUEL OUT

9. Reports

There are 2 reports formatted by TLS 200R which are of interest to Petroleum Officers.

The first, mentioned in the Code of Practice, is the Daily Reconciliation Report.

This report is printed out automatically each day at a preset time. It is a record of the safety reconciliation performance for each tank system for the previous 24 hours. A sample of this report is shown in figure 5.

The second report is available on demand through use of a key. This key would normally only be available to Petroleum Officers, user company senior managers and approved maintenance engineers. The report details the alarm history and system status history as as . 1 1 A sample of this report is shown m inventory eve s. figure 6.

10.

Svstem Features & Benefits

• 1 f brt'dging the gap between the needs of In Its ro e o Of.f.cers and petroleum retailers. the TLS Petroleum 1 ' .. f"ers a number of features and benefits. 200R system o ,, II the various product alarms and reports As we as 1 , t the TLS console It can also be fully availab e <1 • . d · t the chosen management system. This can mtegrate m o , .. be the POS system. the pump controller. a back tem or externally to a central computer via compute1 sys d Ill addition the system 1s equipped with mo em. · lieiist·\,.e self-diacrnost1c and engmeers d1agnost1C comp1 e · · <=- • • • • l Although these may be tronted by automatic too s. reports they are p_rim_arily. available only by use of the system key to avoid

There are a number ot spm-ot-1 bendJts \Vh1ch L'nhance the TLS 200R. In particular. the system ·s need to calibrate itself automatically prior to carrying out reconciliation eliminates the need for e\.pl'nsin:-. tirnl'consuming wet calibrations. With this very highly tunl'd electronic calibration rnmes a Vt'I') high dcgrl'l' of confidence in the ullages shown by the system. is an essential element of Driver Controlled Deliveril's and v. ill on all sites. irrespecti\·c t'f DCD. 1-enllWL' tlw equipment factor from on•rfill situations.

SAFETY RECOHCILIATIOH - TYPICAL PERFORMANCE

With major international markets calling for leak detection/environmental protection packages, tank gauging has entered a new era.

The UK needs have been identified as a commercial mix to satisfy both retailers and safety authorities in a largely non-legislative market.

Specifically, the Petroleum Officer requires a dynamic tank and line monitor which is capable of ensuring safe operation on a 24 hours operating site.

Field trials have clearly shown that the TLS 200R principal of safety reconciliation fulfils the dynamic UK safety requirements. As a fully-featured tank gauge system it also provides the retailer with a full array of wetstock management options.

RECON REP(RT

-20 (1 F:

LEVEL SENSOR

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1 i : t. 11 : '? 11:32 DATA oo: (1 (1(1: (1 (1 (1 : (1 AUiF.:t-1 i 4: 2 j4:13 14: 1 ::: HLAF'il 11: 32 1 i : :: :: 0 '2 i' ·:::·? 0 .-. 1 .·· 1 5 : 5 H H·-· l:JH T EF.' HL HF:tl . ·oo. ·oo '(1 (1, (1 (1 oo. ·oo (1: (1 O: 1.:1 : (1 L. • '1' -'

Hydrocarbon Sensing for Detecting Leaks in Underground Storage Tanks and Pipes

Raychem Corporation

Raychem Corporation of Menlo Park, California is a 30ye_ar-old Fortune 500 company with expertise in material science. The company focuses primarily on heat recoverable plastics,_ conductive polymers, shape memory alloys and fiberopt1c communication systems. Raychem employs approximately 10,000 people and has manufacturing, R&'D administrative operations in the United States, the United Kmgdom, France, Germany, Belgium, Denmark and Japan. Customers are served through sales and technical service offices in 50 countries.

Raychem manufactures and markets a broad range of high-performance products products that are supplied in more than 100 countries to builders and operators of electric power systems, telecommunication systems process plants mines b ·1d· ' ' ' ui mgs, gas and oil pipelines and transportation systems, as well as to manufacturers of electrical and electronic equip t · men , aircraft, automobiles and defence systems.

Tek Products Group has extensive experience in apphcatmns involving the monitoring of pipe trenches and tanks for leaks f 1· ·d o 1qu1 s and wastes. Trace Tek systems are mstalled world ·d · h w1 e m t ousands of commercial buildmg sites mdustrial d · · . ' an process plants, laboratones, retail petrol stations and semiconductor fabrication facilities.

Heinrich Koppitsch

Heinrich Kopp"t. h · R 1 sc 1s aychem's Trace Tek Products Group bus· ·. · mess manager for Europe. He started with Raychem in 1980 and has worked in various sales and marketing p · · S os1t1ons m Germany France and the Umted tat · ' de es to his current position. He holds an Dipl.Ing. gree m gene I . . d . B ra engmeenng and a Masters egree m us1ness Ad · · · · ministration.

IIYDRocAR LEAKS IN BON SENSING FOR DETECTING PIPEs' UNDERGROUND STORAGE TANKS AND

Abstract

In recent Years leak hecome in.. : detection on fuel tanks and pipes has c1eas1ngJ · environment g Y important as concern for the . rows and ... stnngent regul· t. • as a result, countries develop more .. . . a1ons torth . . I his paper describ . . e storage of petroleum products. es a method wh· h d ..,tage while at the ic etects leaks at an early same time · · · · t'll v 1ronmental cont. mmim 1s111g the I ikel ihoocl of L leanup <1mmation and the need for costly

1'111.., lechnology for de , tect 111 g leaks on underground ,,, iraut· lank;, and doubt, · · e containment pipes utilises a d1 111ht1ll'd '>l'm111µ cahle to detect h<)th 1· 11 k f · ·d ue ea s rom 111s1 e " 1 i1 pipe a.., \\ell as water ingress from outside the

containment area. The sensors use conductive polymer coated wires integrated in the sensing cable. These are capable of detecting leaks anywhere along the length of the cable.

Together with the electronic control unit, the system can distinguish between fuel and water contact. The alarm signal can be used to trigger local and remote alarms and to interface with other security systems.

Background of the problem

The problem has its origin in the fact that underground petroleum product storage tanks and pipes are subject to corrosion and other structural damage. If not quickly detected and repaired, leaks of petroleum products can extremely serious environmental damage and economic loss.

The problem is widespread. One study, for example, found that in New England in the United States "aged and perhaps leaking petrol storage tanks are everywhere. These include not only the tanks of retail petrol stations but also tanks owned by bus and taxi companies, agricultural concerns and municipal, state and federal agencies." Another report states that tens of thousands of tank systems in the United States are currently leaking.

The major concern this raises for environmental agencies is that domestic drinking water might be contaminated if the ground water which supplies the aquifers and well becomes contaminated with leaked hydrocarbons and fuels. The same study from the U.S. concluded that leaking petroleum storage tanks could destroy "vast portions of New England"s groundwater in the next five years." More than I, I00 water wells in the U.S. have been closed due to contamination.

Moreover, once it reaches basements, tunnels or sewage systems, leaked petrol poses the potentially catastrophic danger of explosion and fire. This is especially true in urhan areas.

In response to the problem. governments have created regulations for the installation and operation of underground petroleum storage tanks and pipes. and industry has to improve its products. operations and controls. These ettorts are being continued.

Industry's response has also heen to develop new products · h h · hlems What is needed and technnlog1es to cope wit t e p10 · · · in light of this problem are systems which detect hoth ma_1or ·II le·1k cm c·1use 0 rave and minor leaks, since even a smd ' ' ' · '=' damage over a long period of time if it goes undetected.

Since this is a large. widespread and potentially very cost I} problem. it is essential that any solution implemented he well-considered. and that the hest avai lahle and most updo-date technology is used.

Presented at Petroleum Seminar and Exhibition "Safety and Environment at Petrol Filling Stations" 3rd October 1989 Dunstable, Bedfordshire by Heinrich Koppitsch

New regulations in the US

One example of how governments have dealt with the problem can be seen in the United States, where the Environmental Protection Agency has adopted regulations which apply to approximately 1.4 million UST systems storing petroleum and chemicals. The federal regulations govern tank and pipe construction, installation, maintenance, leak detection, cleanup and financial responsibility.

According to federal rules there, all new USTs must now be protected against corrosion and equipped with devices to prevent spills and overfilling. These tanks must also be equipped with some way of monitoring leaks. Existing tanks must be upgraded or replaced within ten years.

Several states in the US are implementing their own standards that are even more stringent than the EPA regulations. For example, California, New York, Florida and New Hampshire now require that all USTs, including piping. have a second containment. Depending on the state, this may be in the form of a double wall tank or pipe, or it may be a plastic liner or concrete containment installed beneath the system. These states also require some type of interstitial leak detection system. Many larger companies as well as public utilities and public agencies are choosing to exceed the regulations because of concerns regarding liability. reputation and financial risk involved.

Alternatives for leak detection in underground storage tanks and pipes

What are the alternatives available? There are several recognised methods of leak detection. Soil petrol monitoring and groundwater monitoring devices use wells located near the UST systems, and are checked periodically for contamination. This method provides detection only after the fact: after hazardous fluid has been released into the surrounding environment. Furthermore, new leakage cannot always be distinguished from previous contaminati';n, nor is

it possible to pinpoint which tank is the source of the contamination. In addition, monitoring wells provide infonnation from a limited number of points only, and released fluid might well move through the ground without hitting one of the installed wells.

The effectiveness of testing tank tightness, which is also known as precision testing, is highly dependent upon the frequency with which it is carried out, and represents only a spot check as opposed to continuous monitoring. Due to its inconvenience, since the tanks cannot be operated during the testing procedure, and the amount of time required for carrying out the test, people often end up waiting as long as possible between tests.

In-tank monitoring, or inventory reconciliation, whether manual or automatic, is an indirect method of leak detection. It is primarily used for controlling the input/output balance of the liquid stored in the tank. But unexplainable differences in the balance mioht result from uncontrolled loss of fluid through leaks. to the tolerances involved with liquid level measurements and other factors influencing the measurement results and accuracy, only a significant amount of loss over a short period of time can be detected. W Ith exception of some very recent m microprocessor-controlled devices, in-tank mornt_onng is not suitable for detecting small leaks from petrol station tanks. Experts around the world agree that the of protection is afforded by double-wall tanks with a contmuous automatic sensing system between the inner outer walls. Unlike methods that depend on a leak rate high enough to trigger a field monitoring device. secondary containment and interstitial monitoring make it possible to detect leaks before hazardous fluid is released into the environment. The measurement is not influenced by existing soil outside of the containment. The absolute volume of fluid released triggers the alarm, which means that very small leaks can also be detected.

A variation of this system is interstitial monitoring between a tank system and an interception barrier, e.g. a basin-shaped liner, a concrete vault or a concrete casing around the tank. Interception barriers may remain vulnerable to punctures, tears, cracks and, if made from concrete, may allow water and fuel penetration over time.

The leak detection system to be presented here utilises a distributed sensing cable that reacts to contact with water or hydrocarbons. It allows for continuous, automatic monitoring of critical areas such as trenches, sumps or the interstice of contained tanks or pipes.

The TraceTek distributed water and hydrocarbon sensing cable

The T;aceTek distributed sensing cable incorporates .s advanced conductive polymer and radiation processes. Two sensors form the core of the sensmg cable. The sensing wires are coated with a conductive poly?1er while the polymer coating of the fuel sensmg dnver swell · h s m t e presence of hydrocarbons. Two filler rods provide th e proper sensmg cable core spacmg. A fluoropolymer monofilament outer braid makes the cable strong and rugged It 11 1. . · a ows 1qu1d to flow through to the sensmg wires but p . . b revents mc1dental contact with metal o

In its petrol station f" . If con 1gurat1on, the sensing cable is used as a se -momtonng w t d h b 1. . . a er an ydrocarbon sensor with the capa 1 1ty to d1stmg · h b hydrocarbons Th etween the presence of water and between the f 1 e va_ue to ?e measured is the current flow normal .dnver and the sensing wire. On a "t . g ble without a detected leak a very small morn onng current flow d fi ' that connects the two ses, .e me? by a cable integrity resistor, cable. If a cab! b k nsmg wires at the end of the sensing become zero e rea occurs, the monitoring current will

W and the system triggers the "sensor out" alarm ater or any el t 1 · I h ec ro yt1c contact will cause an e ectroc em1cal reacti b reaction will indu on the two sensing wires. This I I ce an add1t1onal current flow through the e ectro yte. A current c . . . · d. 1 omparator c1rcu1t m the control unit imme iate y tnggers a water leak alarm

When hydrocarbons co t· h f . . . . · n act t e uel sensmg dnver its cross-lmked elasto · · ' fl · i:nenc Jacket starts to swell. The outer uyoropolymer braid of th . . II" f . e sensmg cable restrains the outer s"'.'e mg 0 the rod. It comes in contact with the sense Wife and estabhshes a I . · ow resistance shunt m the circu1t, which causes fuel leak ala T . . . rm. yp1cal response time at 20°C 1s under 15 mmutes for t 1 ( · pe ro unleaded regular) and less than

FUEL/WATER SENSOR FUNCTION

Lead Wire (2) Red "Spacer" Overbraid

60 minutes for diesel fuel (D-2 control fuel from Phillipps Petroleum).

The current comparator logic gives preference to the fuel alarm over the water alarm. Fuel contact occurring after water contact will always result in a fuel leak alarm. Test results show that the fuel sensing driver also swells in the presence of concentrated vapours with a saturation greater than 60%.

In order to limit sensing cable degradation while it is immersed in water, the sampling cycle of the measuring circuit has been electronically reduced to one in 1000 seconds. Service life test results predict that this increases service life to over 20 years. Once exposed to hydrocarbons the product is not reusable, and the manufacturer recommends replacing the cable. The sensor can be used in an ambient temperature of up to 35gC. The temperature coefficient of the elastomer expansion causes the sensor to be temperature sensitive above t_his range. .

The electronic control umt uses a 7 VDC source. This, together with current limi.ting at. ca?le terminals, fulfils the requ!fements of safe c1rcu1ts. Each sensing cable has its own alarm type of alarm, e.g. fuel leak, water leak, out, 1s md1cated by common alarm indicators for all c!fcuits.

The use of distributed water and hydrocarbon sensing cables in petrol stations

As mentioned above, the highest degree of protection and economic efficiency is provided ifthe sensing cable is used in the interstice of double containment tanks and pipes. The system monitors and opera.tes of the normal operation of the petrol stat10n. The increased cost over a single containment tank is often offset by the reduced environmental and financial risk for the owner of the petrol station and by the fast and precise action possible due to the clearly defined sensor environment.

The cable is installed in a double-wall steel tank along the entire length of the vertical monitoring pipe on the front side of the tank. The sensing cable signals alarms in the presence of fuel leaking through the inner tank shell as well as when water infiltrates through the outer wall containment. The sensing cable can detect a layer of fuel even when water is already present. For reason, the cable is i?stalled from top to bottom the entire !ength of the monitoring pipe. The sensing cable 1s also used m sumps or other collection areas e.g. in manholes, under islands or at the point of double containment pipes.

Even on new petrol stations, TraceTek sensing cables have detected leaks due to installation problems on valves and fittings, and have discovered cracked tanks, damaged vents for double containment tanks, and petrol station maintenance problems resulting from fuel emptying into containment trenches. Moreover, leak detection systems have also helped petrol station owners prove that fuel detected in nearby groundwater was not released from their tanks, but instead originated from other sources in the neighbouring area.

In one instance, an inventory balance showed missing fuel, which would normally require an immediate check for leaks together with a tank shutdown for several hours. But the leak detection system installed did not signal an alarm. A was made and the error was found. The petrol station owner was quoted as saying that "the system has already paid for itself." One point to be made in this respect is that inventory reconciliation does not make detection redundant or vice versa. On the contrary, only both measures together provide the necessary amount of information and degree of protection.

Other uses of conductive polymer technology in leak detection

As far as other applications are concerned, sensors have been developed which monitor and locate a variety of hazardous liquids. The TraceTek 300 line detects all conductive liquids including acids, bases, water, essentially all aqueous chemicals and liquids which contain substantial amounts of water. The TraceTek 500 series of sensors detects the presence of hydrocarbons while ignoring water and aqueous chemicals.

Four-wire sensing cable and conductive polymer technology is used to detect and locate fluid contact anywhere along the length of the sensing cable. Voltage and current measurements allow conversion of resistance values into distance readings regardless of the leak distance or fluid resistivity involved. Since the cable is constructed of fluoropolymer materials and no metal is exposed to the environment, the sensing cable is highly resistant to most chemicals and to corrosive environments.

A complete line of leak location systems is available, as Well as systems offering alarms only. Longline location systems up to 500 metres in length use connectorised cables that s· I 1 h : imp Y plug together. The distance to the leak a ong t e sensing cable is displayed with an exactness of plus or minus These systems typically monitor pipes or subfloor as. Using the branching capability of the system, even complex sy ·t ·1 b · s ems, multiple pipes or pipes and tanks can eas1 Y e handled z 50 d. t I · one locating systems monitor up to 1scre e ocat1ons w·th . d k · 1 one control unit. Applications mclu e tan s, valves and · . · ' equipment areas in all kind of industnes.

Conclusions

The TraceTek water and hydrocarbon sensor has proven to be a significant advancement in the technology available for leak detection. The distributed sensing cable enables differentition between water and fuel leaks. Its strong and rugged construction without use of mechanical parts makes it especially suited for the petrol station environment.

Used in double-containment tanks and in pipes in pipe trenches or sumps, or in areas with an interception barrier to the environment, this leak detection system provides the greatest possible degree of protection.

TraceTek leak detection technology is suitable for a wide range of applications requiring leak location or leak detection only. TraceTek products are exai:nple _of how new technology and innovation helps m deah_ng with one of the most serious environmental problems facing us today.

Source of Information

The Federal Register, Vol. 53, No. 185, Sept. 23, 1988. Part II, Environmental Protection Agency, 40 CFR Parts 280 and 281. "Underground Storage Tanks; Final Rules."

Hazardous Materials & Waste Management Magazine, May/ June 1986, pp. 16-19, 33-35. "New UST Regulations Will Help Safeguard Our Groundwater," by Robert J. Keegan. "Secondary Containment New Tool for War on Groundwater Pollution," by Austin M. Snow Jr.

The Boston Globe, Feb. 13, 1985, pg. 17, "Underground Time Bomb, Aging Gas Tanks Imperil Water Wells," by Dianne Dumanowski.

Pollution Engineering, July 1987, pp. 54-61. "Quantitative Risk Evaluation of Underground Storage Tanks," by J. G. Cassana, R. P. Ouellette and P. N. Cheremisinoff.

Raychem Corporation, Qualification Report for TraceTek Sensing Cable Type VR-5, No. 1510, April 1989.

Raychem Corporation, Qualification Report for TraceTek Sensing Cable Type VR-5, No. 1510, April 1989.

Raychem GmbH Trace Tek Products Group

Corroshield have been lining petrol storage tanks for over a decade endorsing our quality of specification and experience in this specialist field

Corroshield System 80 tank rehabilitation is not a repair or temporary solution: (it is new tanks for old) backed by our guarantees extended for as long as you require

In any forecourt operation tank protection should be as t.ank and subsequent replacement could wipe out years of profits and impose immediate financial burden.

DON'T WAIT UNTIL IT HAPPENS: Ring now for details on how we can provide protection for your underground storage facility at very little cost.

CORROSHIELD

Unit 1, Hackers Close, East Bridgford, Nottingham NG13 8PG Telephone: (0949) 21032

COMMERCE HOUSE, THE MALTINGS, STATION ROAD, SAWBRIDGEWORTH, HERTS. CM21 9JX Telephone: 0279 723448