Forecourt Trader
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Flowing underground

06 January, 2006
Tanks and pipework may be out of site, but never out of mind
Page 27 
Tanks and pipework might make up the unseen part of the forecourt, but nothing is more integral to the successful operation – and safety – of the site. Tanks and pipes are governed by strict regulations, which mean retailers must keep an up-to-date written risk assessment of underground equipment and commit to maintain it.
Although no two sites are the same, there are common areas that retailers should pay close attention to.Huw Carey of Torex Retail Forecourt Services (RFS) says the nature of most forecourt sites means problems can come to the fore after years of smooth operation: “Until a few years ago, when the Institute of Petroleum (IP) recommended discontinuation, all petroleum retail outlets had single-skin underground storage tanks (USTs) and galvanised steel pipework installed. USTs were painted with a black bitumen coating before installation and tanks were retained in the ground by two main methods – the first was to put the tank in a brick vault secured by steel straps and surrounded with washed sand. The other was to excavate, install a concrete base, again with steel straps, and surround the tank with sulphate-resistant concrete.”“For the pipework, galvanised steel tube was cut, screwed and connected together using mechanical joints and a jointing paste. This was surrounded by sulphate-resistant concrete (to minimise the effects of corrosive salts in the ground). Tanks and pipework were pressure-tested prior to commissioning and the pass certification held on file by the Local Authority Petroleum Officer.“Years of trouble-free operation have gone by,” explains Carey. “But a number of problems have been quietly building up in the background.“Tanks by their very nature of having their vent pipes connected to atmosphere and their bulk in the cold earth create condensation on the ullage space surfaces; this water causes rust on the exposed surfaces and also runs down the inside of the tank walls and collects below the internal suction pipes. The use of leaded petrol in tanks leaves sediments, together with rust particles lying at the bottom of the tank. Some petroleum products have also been known to promote bacterial growth.”He adds: “Over a number of years the combination of all the factors means internal surfaces of tanks corrode and pit, eventually leading to failure, either having water ingress above the product level or leak of product into the surrounding ground causing contamination and huge clean-up costs.“Deterioration of the tank coating and reaction between the steel straps and tank can also mean that there are corrosion points on the outer surface. Torex RFS, for example, has replaced a number of underground tanks because, due to corrosion, they have failed pressure tests.”“Cutting and threading galvanised pipe exposes the steel below. Impurities and foreign bodies in the material surrounding the pipework, together with ground movement and vibration, gradually erode the integrity of the concrete allowing water to come into contact with steel, again corrosion results causing priming problems with the pumps and ground contamination.”Because Torex RFS specialises in repairing or replacing corroded pipework, Carey reckons a sensible approach to maintenance can help spot these common problems as soon as they occur.He says: “To minimise problems, site operators should have their tanks regularly dipped and checked and then have any significant water removed. At the first sign of priming or ‘fall back’ of product in the pumps, suction lines should be pressure-tested to confirm their integrity.“This is all very much a case that a small investment on a regular basis can be very worthwhile, as it can result in massive long-term cost savings from both a replacement and clean-up perspective.”CLEANINGPaying regular attention to tanks and pipework is vital, and a key part of maintenance is cleaning.Kathy Early, managing director of tank cleaning and decommissioning specialist David Plumb and Co, says: “Every year, thousands of forecourt operators are wasting money on emergency tank cleaning and unnecessary service callouts to unclog pumps, all of which could be avoided by regularly checking and cleaning tanks and lines.“Usually, customer complaints about dirty petrol and clogged pumps failing to dispense, are blamed on faulty filters and bad loads. Often, retailers will carry on struggling until engineers are being called out every week or the pumps refuse to work altogether. At that point, we get called in to carry out emergency cleaning, which means a service station can be out of action for days. In some cases it also means that the pumps have to be replaced.“By simply having petrol storage tanks cleaned about once every 10 years, and diesel tanks every eight years, forecourt operators can avoid all these costs and problems, and escape the extra corrosion problems associated with dirty tanks.”Early says the whole process, which costs around £2,000 to £4,000 per forecourt, can be achieved with minimum disruption.“For safety reasons the forecourt has to be closed to customers for part of the process, but this can be kept down to less than a working day, or under two hours if only a single tank is cleaned,” she adds.The technique David Plumb & Co uses starts with filling the tank with inert foam to drive out all the residual fuel vapour. Once this foam dissipates, it leaves behind an easily removable residue. The inspection hatch is then removed and an operative, wearing full breathing apparatus and personal protection equipment, goes into the tank to clean it manually.If you are not sure whether a tank needs cleaning or not, the company offers a testing service. For around £80-100 per tank, David Plumb will professionally test and report on a site to ensure sediment levels in the tanks are not becoming dangerously high, heading off possible repair bills and damage claims.During the test, the company takes three samples: one from the dispensing nozzle, one from 40mm off the bottom of the tank and one from 20mm. It tests for both water and particulates and produces a plain English statement of condition, which gives the site operator a snap-shot of the condition of their tank.Eurotank Environmental, meanwhile, offers retailers a ‘tank doctor’ service including internal inspection, tightness testing, water removal, microbiological contamination removal and biocide dosing of tanks. The company uses endoscope inspection equipment, which it describes as ‘CCTV for explosive atmospheres’. Designed to operate in the most dangerous part of a fuel tank – the ullage space – Eurotank uses this equipment for removal of water, silt, sand and light sediment from above- and below-ground fuel tanks, without removing the lid or entering the tank. The company also carries out ultrasonic vacuum tank testing for tank tightness.TANK LININGLining existing tanks can be a cheaper and less disruptive alternative to replacing faulty tanks.The Graphite Tanklining system, for example, involves installing a single- or double-skinned continuously monitored fibreglass lining in existing tanks. The tank interior is grit-blasted before a succession of fibreglass linings are installed (including a patented interstitial material), providing the space to be monitored by the vacuum, once the job is complete. The final coating is warranted to be proofed against the latest euro fuel standards.At the same time as the lining is completed it is possible to also carry out other works including rebuilding tank access chambers, replacing pipework if necessary, reinstalling or supplying new tank gauges and other associated works.Graphite recently introduced a new monitoring system, which sends regular test text messages to a designated mobile to show the system is operative and also to send a warning should there be a breach in the interstitial space.A spokesperson for Graphite says: “A tank lined with a double-skin fibreglass constantly monitored interstitial system is a guarantee that you are not only protecting your substantial investment in fuel but also making sure that you are doing all you can to protect the environment.”PIPEWORKTraditionally, pipes serving fuel tanks were made of steel, which, while strong, was prone to problems such as inflexibility and corrosion not to mention the high cost. Today, specialist new materials can offer a better solution for pipework.PetroTechnik, for example, says it has now laid more than six million metres of its Universal Petro Pipe (UPP), without a single drop of fuel lost to system failure.The company says the UPP system is a ‘complete leak-tight sump-to-sump system that will last the lifetime of the site ensuring cost-efficient fuel delivery and complete protection for the surrounding environment’.A spokesperson for Petrotechnik says: “Electrofusion, or welding by electricity, lies at the heart of the system connecting pipe and fittings together to create seamless direct-burial pipework systems.“Each socket has a heating element so that when electrical heat is provided through a specially designed welding unit, the joint and pipe interfaces melt and fuse. During the cooling process the polyethylene solidifies to form a homogenous union.”The UPP system includes pipework, sumps, chambers, entry fittings, access covers and leak detection and all UPP installations are vacuum testable at the point of installation and during operation.The company also supplies a secondary containment system. A spokesperson for Petrotechnik says: “Using duct piping allows UPP pipe runs to be retractable without breaking concrete if subsequent alterations need to be made.”COMPLETE SYSTEMSComplete or ‘ready-made’ forecourt systems can be an attractive option for a retailer who wants to start from scratch – perhaps they’ve got a completely new site or an existing site is undergoing a refurbishment.PetroTechnik’s Petrofast system, for example, available in the UK through Cookson and Zinn, is based on pre-engineered, pre-fabricated modular components incorporating storage tanks, pipework and associated equipment, and can also include canopies and pump bases.The canopy mountings are fixed to an external rolled ring, which terminates with base support saddles. The support saddles, together with the reinforcing bar and a mesh are sunk into the concrete, eliminating the need for pre-fitting of holding down straps or pre-laying concrete bases.Each system is factory assembled for rapid on-site installation. Because site work is kept to a minimum, PetroTechnik says cost savings can be achieved while at the same time, the quality of construction is also enhanced.The modular design can be tailored from basic units to suit any size or type of installation. This enables customers to specify the level of pre-build they require.