Finding, however, that the need for having the acetylene under pressure
somewhat limited the sphere of usefulness of his apparatus, Fouche
finally designed a low-pressure blowpipe, in which only the oxygen
requires to be in a state of compression, while the acetylene is drawn
directly from any generator of the ordinary pattern that does not yield a
gas contaminated with air. The oxygen passes through a reducing valve to
lower the pressure under which it stands in the cylinder to that of 1 or
1.5 effective atmosphere, this amount being necessary to inject the
acetylene and to give the previously mentioned speed of escape from the
blowpipe orifice. The acetylene is led through a system of long narrow
tubes to prevent it firing-back.
AUTOGENOUS SOLDERING AND WELDING.--The blowpipe is suitable for the
welding and for the autogenous soldering or "burning" of wrought or cast
iron, steel, or copper. An apparatus consuming from 600 to 1000 litres of
acetylene per hour yields a flame whose inner zone is 10 to 15
millimetres long, and 3 to 4 millimetres in diameter; it is sufficiently
powerful to burn iron sheets 8 to 9 millimetres thick. By increasing the
supply of acetylene in proportion to that of the oxygen, the tip of the
inner zone becomes strongly luminous, and the flame then tends to
carburise iron; when the gases are so adjusted that this tip just
disappears, the flame is at its best for heating iron and steel.
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