An Investigation of Oxy-Acetylene Welding and Cutting Blowpipes
R. S. JohnstonAbstract
This paper reports the results of and conclusions from an elaborate series of tests carried out at the Bureau of Standards Washington, D. C. on commercial apparatus for cutting and welding by the oxy-acetylene process, submitted by manufacturers for the purpose of the tests.
The test equipment used consisted of a weighing system for determining the weight of the gases used, a system for metering the gases as a check upon the weight and for maintaining standard conditions of pressure and temperature, a welding table for the welding tests, a cutting table for the cutting tests, and a “flashback” and safety testing apparatus for determining the conditions of the flashback phenomena.
Unusual precautions were taken to insure accuracy in all the tests. For example, the cutting tests were all made by a mechanically controlled cutting device installed on the cutting table, to eliminate the personal equation.
The welding tests were performed upon ½-in. and ¾-in. steel plates, and the cutting tests upon ½-in., 2-in., 6-in. and 10-in. material.
The general conclusions from the tests were that there was a great deal of difference between the characteristics of different designs of cutting blowpipes, and that there was no make of apparatus which was equally proficient and economical for all thicknesses of metal. Further, one of the prime essentials of a good welding blowpipe is its so-called gas ratio, which should be unity. Not any of the blowpipes tested proved capable of maintaining a gas ratio of unity during welding although, as the author states, the welds were probably made with greater care than has ever been bestowed upon any like work.
The important problem of “flashback” receives extensive consideration, and the author concludes by stating that experience gained during these tests indicates that a blowpipe designed to be absolutely free from flashback caused by any form of obstruction, under all working conditions, will also be the eminently safe blowpipe and the one which with ordinary care will produce sound welds. Such a blowpipe will be one so designed that, under all conditions of operation — even to complete blocking of the gas exit at the tip end, there will be maintained a one-to-one volume delivery of each gas, at identical pressures.