Preventing Trouble in Gas Producers
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Precautions Which Should Be Taken in -Order to Avoid Extensive Damage and Repairs
BY giving early attention to minor faults which may develop in a gas producer, repairs, which may be costly in time and labour, may be avoided. Air leaks are almost impossible to detect by -visual means, and, whereas small leaks in the system from the first cooler to the engine are undesirable, they are not usually of serious consequence.
Leakage of air into the producer, particularly in the lower part near to the fire zone, should receive early attention as the fire will, naturally, tend to travel towards the point at which the air is entering. The fire will spread until the heat developed may be such as to cause a hole to be burned through the producer casing at the Point where the leak originated.
Probably the most likely sources of such trouble are the welded joints, gradual thinning of the firebox material, or badly fitting door or flange joints. Pressure testing is the obvious way of discovering such leaks and, to conduct such a test in the case of a p.s.v. producer, it is necessary toseal the tuyere and the "gas off-take hose running from the trailer.
In the case of the latter, this can be done by means of wooden taper plugs and, for ihe tuyere, a rubber
bung, expanded by means of a wingnut on a threaded rod, and a guide tube of sufficient length to project outside the flame box, can be used. Quite a low pressure, say 5-lb. per sq. in., is sufficient: and the simplest method of carrying this out is to adapt a filter filler cap with a tyre valve, or in the plug used for sealing the off-take hose.
A pressure gauge and a tap for releasing the pressure are also necessary The air may be supplied by a tyre pump or compressed-air supply, a necessary precaution with the latter being the fitting of a safety valve set to blow off at-about 7 lb. per sq. 'in.
Any bad leaks will become evident by the audible sound of escaping air, the necessary steps being taken to rectify any which may be, discovered. A producer that does not lose more than 1 lb. pressure in 5 mins. may, to all intents and purposes. be considered as airtight.
lu. the case of leaks of a minor character, soapy water may be applied in the suspected areas or a small flame from a gas jet may be used. Particular attention should be paid to the bottom door joint and the tuyere flange joint.
It is important that a pressure test should not be carried out when the filter has been filled With water, as there is a danger that water may he forced back into the coolers as a result of an air leak being present in the cooler or hopper sections of the unit, by the pressure being released by the tester from the .tuyere orifice; or, more particularly, if the air pressure be applied at the take-off hose or filter filler cap.
An uncommon source of leakage comes from an imperfectly fitted filter filler cap. Should there be a leak at this point the cap should be removed and refitted after a pressure test, in order to permit of the filter being filled with water before commencing service.