❞ كتاب اللحام و القطع بالأكسي استيلين AN INTRODUCTION TO OXY/ACETYLENE WELDING AND CUTTNG ❝

اللحام والقطع بالأكسي استيلين

Introduction
Oxygen/Acetylene welding, or “Gas Welding”, is a pr
ocess which relies on combustion of oxygen and 
acetylene. When mixed together in correct proportio
ns within a hand-held torch or blowpipe, a hot flam
e is 
produced with a temperature of about 3,200°C. The c
hemical action of the oxy/acetylene flame can be ad
justed 
by changing the ratio of the volume of oxygen to ac
etylene, using the valves on the torch or blowpipe.
Equipment
Oxy/acetylene equipment is 
portable and easy to use. It 
comprises oxygen and acetylene 
gases stored under pressure in 
steel cylinders. The cylinders 
should be fitted with regulators, to 
control the pressure and flow of 
gases. Flexible hoses are used to 
connect the regulators to the torch 
or blowpipe. Specially designed 
safety devices, called flame traps 
or “Flashback Arrestors” are fitted 
between the hoses and the 
regulators. Flashback arrestors 
prevent flames generated by a 
'flashback' from reaching the 
cylinders 
Flashbacks
A flashback is a rapid, high-
pressure flame travelling back up 
the gas hoses, caused by welding 
or cutting at incorrect pressure 
settings, or from blockage or 
overheating of the nozzle (for 
example by operating with the 
nozzle too close to the material) 
Flashbacks can result in extremely 
dangerous cylinder ignition and 
must be prevented by proper use 
of working Flashback Arrestors. 
Lighting-Up Procedure
To begin oxygen/acetylene welding or cutting, open 
the 
cylinder valves slowly by means of the cylinder key
(s).  
Do not open suddenly or there may be serious damage
 to the regulator and the possibility of an acciden
t.   
Open the cylinder valve spindles one turn only.  Op
en the fuel gas control valve on the blowpipe and a
djust the 
regulator to give the correct working pressure (see
 chart on page 13), this ensures that any air or ox
ygen is 
purged from the hose. Repeat the procedure for the 
oxygen side. 
Light the gas by means of a suitable sparklighter m
aking sure that the sparklighter is held at right a
ngles to the 
nozzle.  Do not use liquid igniters (such as cigare
tte lighters) as the vapour/gas combination can be 
dangerous. 
Reduce or increase the acetylene supply to the blow
pipe valve until the flame just ceases to smoke. 
Slowly increase the oxygen via the blowpipe control
 valve until the white inner cone in the flame is s
harply 
defined with the merest trace of an acetylene haze.
 The blowpipe is now correctly adjusted
 

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