ROAD AND WORKSHOP by HANDYMAN
Page 37
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Air Storage Tanks on Vehicles and Trailers
FOR many years now the stationary air receiver has enjoyed regular shortperiod examination, pressure testing at programmed intervals, and whether in garage, aboard ship, or working at the roadside, it is fully covered by insurance.
It is, therefore, something of an odd situation to find other air-storage tanks with working pressures at more than the 100 lb. being fitted in their thousands to vehicles and trailers---and whilst these tanks are just as lethal as their stationary counterparts, there are no set rules for testing them, or even provision made for internal inspection. Yet they are subjected to operating conditions that at times would make the dedicated insurance engineer shudder. Despite the fact that accidents are rare it is still a certainty that if a tank does let go it can blast up a section of vehicle floor, or punch in the rear of a cab with no bother at all.
There is an incident on record where an air reservoir that had rusted behind its straps did in fact suffer a sticking safety valve and exploded, taking with it several floorboards and throwing off cases of bottles. No doubt this equipment will receive, in due course, similar attention to the workshop tank. But in the meantime it is up to the maintenance engineer to take what steps he can to prevent accidents.
The danger from an exploding air tank mounted on the outside of a chassis at knee height need not be described. Nevertheless, precautions should and can be taken. The main risk springs from the tank supported by felt-lined straps and is twofold: the straps can loosen off and movement can wear and weaken the tank: and where a packing of felt or similar absorbent material is used (or even with
the plain straps themselves) rust can form unnoticed and eat through.
A number of tanks on one make of vehicle were prone to moving within their straps. The cure for this was to copy a modification brought out by another manufacturer. This was to lengthen the the draw bolt and fit a strong coil spring between the nut and strap, and place it under reasonable tension.
Where there is danger from water collecting behind the straps, particularly where the tank is not easy to reach for inspection, a layer of Fibreglass slightly wider than the strap can be smoothed on the tank.. This provides both rust-proofing and a good grip. Regular draining is important and it is not true, as some believe, that all water is expelled from the system each time the brakes are used. One recommendation to the manufacturer would be for a suitably sized cap or plug that would permit a thorough internal examination