. Canadian machinery and metalworking (January-June 1919). ressure. Acetylene may also be made on thepremises by acetylene generators whichgenerally work automatically, givingpractically a constant pressure, either 6to 12 inches of water pressure in lowpressure generators or 6 to 15 lbs. inhigh pressure generators. Blowpipes have two inlets which areconnected to rubber tubings, one leadingto the oxygen supply and the other tothe acetylene supply. The two gases which are mixed inthe blowpipe should have a sufficientvelocity at the nozzle so there will be nochance for the flame travelling back i
. Canadian machinery and metalworking (January-June 1919). ressure. Acetylene may also be made on thepremises by acetylene generators whichgenerally work automatically, givingpractically a constant pressure, either 6to 12 inches of water pressure in lowpressure generators or 6 to 15 lbs. inhigh pressure generators. Blowpipes have two inlets which areconnected to rubber tubings, one leadingto the oxygen supply and the other tothe acetylene supply. The two gases which are mixed inthe blowpipe should have a sufficientvelocity at the nozzle so there will be nochance for the flame travelling back in-side the blowpipe, which when it occursis called backfiring or flashback. The speed of propagation of the flamein the case of a mixture of oxygen andacetylene varies according to the pro-portion of the two gases, but it is gen-erally admitted to be around 330 feet persecond, consequently the velocitv of themixture at the nozzle should be abovethat figure to avoid the flashback Onthe other hand, if too high a speed isused, we will have a very hard flame. METHOD OF TESTING BLOW PIPE Kebruary 20, 191» C A N A 1) I A N M A C 11 1 N E R Y 18 • which will .stir the molten metal and willhave a tendency to blow it away, a con-dition which should be avoided. The intimate mixture in the right pro-portion of the two gases, and the avoid-ance of flashback, are very importantconsiderations which require seriousstudy. The construction and ease ofmanipulation are other problems to beconsidered. In the choice of a blowpipe the fol-lowing- points should be investigated:;ype of the blowpipe, power, design,reliability, efficiency, first of BlowpipesBlowpipes can be divided into twogeneral types. The pressure blowpipe re-quiring a medium pressure of varying between 1 and 15 lbs.,and the low pressure blowpipe—alsoailed injector blowpipe—which can workMi acetylene of 4 to 10 inch water pres-sure, that is to say less than half pound,choice between these two typesde
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