CUTTING OFF-ROAD TIME
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With idle time costing upwards of £200 a day and manufacturers reluctant to undertake repair work, independent tank repair and maintenance specialists come into their own, keeping the tanker fleets moving
• Today's tanker vehicles, built for versatility in expensive materials and with elaborate on-board auxiliaries, are costly items of capital equipment. Nothing brings home their value to a transport manager more than enforced idleness, brought about through accident damage, leakage or other malfunction.
When problems do arise, an operator's first inclination is to turn to the manufacturer. But he could well be three or four hundred kilometres away, implying one or more days lost in simply getting the tank to and from the repairer. In any case, though they would not admit it, most tank builders undertake routine repair and troubleshooting work with reluctance, especially when new tank order books are full.
Independent tank repair and maintenance specialists, providing a local but all-embracing service in areas of concentrated bulk transport activity, are rare.
It is not difficult, however, to see more such concerns appearing on the scene, as tank technology advances and legislation is more strictly enforced.
SAS Engineering is one such tanker service specialist. It occupies adjacent premises in the industrial area of Avonmouth, close to the docks and, significantly, within a couple of kilometres of 12 oil company terminals, four of which — Esso, Shell, Fina and Texaco — operate from their own individual sites. SAS undertakes tank repair and refurbishment for most of those companies, and in just over two years some 970 tanks have received attention.
SAS general manager, Roger Adams defines his catchment area as one roughly bounded by Swansea, Milford Haven, Southampton and Tewkesbury.
That throughput of work — nearly nine jobs a week — is particularly impressive, taking into account the fairly modest scale of the operation. SAS has just four fitters and a workshop of 380m2(4.100sqft) able to accommodate no more than four tankers at a time.
Before an oil or fuel tank is allowed inside the shop, SAS carries out a stringent gas (fume) removal procedure. That involves steam cleaning followed by what Adams calls a cold rinse, using "spinner" waterspray attachments which fit into the manlid apertures. Then follows an atmosphere sampling check utilizing an explosive gas detection meter of the kind used in coal mining. The hand-held mine safety appliance (MSA) meter is fed via a long open-ended rubber tube, which is lowered into the tank to "sniff' the air inside.
A check-sheet certificate (an internal document) has to be completed, confirming the gas sample analysis, before the tank can be brought into the workshop and, of course, before anyone can get inside and start welding and/or grinding operations. The certificates are filed for possible scrutiny by Health and Safety Executive inspectors.
The MSA sampler is just one of a range of equipment putting SAS in the "tank service specialist" category. A selection of new welding gear was acquired when Roger Adams joined Portishead Commercials' Bob Scott to launch the SAS venture. Three different welding processes (tungsten inert gas, metal inert gas and manual metal arc) — TIG, MIG and MMA — are available, enabling stainless steel, as well as aluminium and mild steel, tank shells to be repaired or modified.
Stainless steel tanks are being encountered more and more frequently by SAS, as hauliers and petro-chemical manufacturers seek to increase fleet versatility, and hence utilisation. For acid carrying, rubber-lined tanks are now in widespread use, and they pose particular problems for repairers like SAS, when the lining becomes damaged in an accident or through any other cause. Vulcanising of the rubber, and subsequent electrical-continuity testing to check its leaktightness, are sub-contracted to another specialist in Newport.
Much of SAS's work on liquid tanks involves tracing and rectifying leaks. Often they emanate from pumps and valves and call for straightforward replacement of seals. On other occasions, the leaks are more insidious, indicating deterioration in the tank structure.
Gradually propagating fatigue cracks remain a problem in older aluminium tanks. Bad roads, with numerous railway level crossings in and around Avonmouth exacerbate tank cracking problems, especially on leaf-sprung chassis and trailers.
Drilling a small hole at the end of the crack will usually retard its development (regular practice in the aircraft industry), though to block the leak, the crack and hole must, of course, be weld-repaired. As Adams points out, most aluminium tanks are built to carry spi, and, as such, are multi-compartment designs. The most common fatigue cracl cause leaks between compartments, which are not readily apparent.
So-called hydraulic tests are used tc locate small leaks, the tank being fillet with water and pressurised, typically t about two Bar (30 psi). Where there at legislative or safety considerations, pressure checks are often carried out under the supervision of an independer inspector, usually from the Freight Transport Association in the case of spir and oil tanks, and an insurance compan nominated engineer for high-pressure an general-purpose vessels.
Leaks are sometimes more obscure. . 24 tonne rigid steel spirit tank broughl into SAS recently with a suspected lea was indeed found to be losing product. . was seeping through a weld crack into th hollow box-section integral "runners" b which the tank was mounted to the chassis. The technique adopted to trac the leak was to pressurise each runne void from the workshop airline and rut along the weld inside the tank with soa solution, where bubbles quickly shower up the leak.
Mild-steel tanks can and do deteriorat structurally through corrosion. SAS use an ultrasonic meter, giving a digital rek out in millimetres, able to measure the thickness of any mild (or stainless) stee barrel.
Looking to the future, Adams sees a growing volume of tank modification work arising from changes i legislation. In particular, the projected move to bottom-loading of liquid tanks with the need being eliminated for terminal staff to climb on top of vehicles — is likely to mean a lot of modification work.