Much-improved
Page 50
If you've noticed an error in this article please click here to report it so we can fix it.
Degreasing Plant
TRROITGEf the courtesy of the Southern-area distributte*, James W. Carr and Co., Ltd., 26-27, Budge Row, London, E.C.4, we have been able to witness a demonstration of the latest D-type degreasing plant which has been produced by Imperial Chemical Industries, Ltd., . London.
Many readers will be familiar with the older type, examples of which are in use all over the country. The new plant works on the same principle, the chemical employecl being trichlor-ethylene (CJEIC15), which has 4t exceedingly low latent heat (56.59 Cal.) and a high specific gravity (1.471). It is, of course, a fire-extinguisher, and is antiseptic.
In the older type of plant a hinged lid was fitted to the tank, to the underside of which was attached a coil of water piping. The chemical was poured into the base and kept above boiling point (87 degrees C.) by gas flame, electric or steam heating. In addition to the water coils under the lid, a coil was placed in the base of the tank below the grid supporting the parts to be degreased. Whenever the tank had to be opened to replace oily parts for those that had been cleaned, the vapour was lowered by passing cold water through the bottom coil. On each occasion some air entered to take its place, took some trichlor-ethylene into suspension, and was displaced when the vapour was again raised. Opening of the hinged lid also tended to waft some of the vapour away. Apart from the waste, it was inconvenient to lower the vapour for each loading.
Both disadvantages are overcome completely in the new type. In this there is a water coil at the base which is used only at the end of each day. The upper coil, instead B36 of being attached to the lid, passes 11itimes around the upper portion of the tank. Cold water continually circu lates through the upper coil at a slow rate, thus forming a cold zone, which keeps the vapour permanently down in the lower half of the container. This lower part has a double wall forming a hot jacket. Any wafting effect is obviated by fitting sliding covers.
A tray containing about 5 cwt. of greasy parts can be raised or lowered slowly with practically no loss of chemical, because as the hot parts pass through the cold zone, the trichlor-ethylene condenses instantly and runs back into the tank. The advantage will appeal instantly to all who have experience of degreasing work.
Another feature of the plant is that around the inside of the tank, at the base of the cold zone, is a gutter into which chemical condensing on the cold walls constantly pours at the rate of a gallon per minute. Ordinarily, it over flows into the base, but when it is desired to re-distil the trichlor-ethylene, to separate it from the oil and dirt, all that has to •be done is to turn a tap so that the gutter, instead of overflowing, drains its contents out to a can which is stood beside the plant. A thermostat in the boil ing liquor automatically turns out the gas or cuts off the heat at 120 degrees C., so as to prevent the lighter oils from being vaporized with the chemical. A sludge tap at the base is then opened while the mixture of oil and dirt is still warm enough to drain away without difficulty. The complication of separate stills is banished, The standard plant for degreasing i-ton lots in about 17 minutes measures externally 5 ft. 2 ins. by 2 ft. 8 ins.
by 3 ft. 61ins, high, and has a hot-vapour zone 4 ft. by 1 ft. 9 ins. by 1 ft. 3 ins. This plant requires three gallons of liquor (costing about 4s. 5d. per gallon), and one gallon suffices to degrease 1i to 3 tons of parts, according to their size and nature. Four minutes are required to boil the liquor from cold, and in a maximum of 10 minutes the vapour will be "up." Distillation, which needs to be done about once a day or less, according to the nature of the work, takes about four minutes, plus the time for draining off the sludge.
There is another model, in which parts are inserted in boiling liquor. This is useful when a large amount of mud must be washed off and where it is not desirable to render the parts chemically free from grease, as with the vapour-type outfit.
Latest examples of installation effected by James W. Carr and Co., Ltd., have incorporated brushing tables of expanded metal, through which the dust brushed from the degreased parts is extracted downwards to be delivered to a centrifugal dust separator. The tables have rollers to facilitate the handling of heavy parts. Such plant, with electric fans to create the suction, is supplied by the James Keith and Blackman Co., Ltd., 27, Farringdon Avenue, London, E.C.4.