Английский для сварщиков. Гричин С.В. - 82 стр.

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82
kPa (250 lbf/in²) of pressure in the tank when full. Acetylene when burned
with oxygen gives a temperature of 3200°C to 3500°C (5800°F to 6300°F),
which is the highest temperature of any of the commonly used gaseous fuels.
Hydrogen has a clean flame and is good for use on aluminum. It can be
used at a higher pressure than acetylene and is therefore useful for
underwater welding. For small torches, hydrogen is often produced, along
with oxygen, by electrolysis of water in an apparatus which is connected
directly to the torch.
MAPP gas is a registered product of the Dow Chemical Company. It is
liquefied petroleum gas mixed with methylacelylene–propadiene. It has the
storage and shipping characteristics of LPG and has a heat value a little less
than acetylene.
Oxygen is not the fuel: It is what chemically combines with the fuel to
produce the heat for welding. This is called 'oxidation', but the more general
and more commonly used term is 'combustion'. In the case of hydrogen, the
product of combustion is simply water. For the other hydrocarbon fuels,
water and carbon dioxide are produced. The heat is released because the
molecules of the products of combustion have a lower energy state than the
molecules of the fuel and oxygen.
Oxygen is usually shorted to 'oxy' for use in the term 'oxy-acetylene
torch'. Oxygen is usually produced elsewhere by distillation of liquefied air
and shipped to the welding site in high pressure vessels (commonly called
'tanks' or 'cylinders') at a pressure of about 21000 kPa (3000 lbf/in² = 200
atmospheres). It is also shipped as a liquid in Dewar type vessels (like a large
Thermos jar) to places that use large amounts of oxygen.
It is also possible to separate oxygen from air by passing the air, while
under pressure, through a zeolite sieve which selectively absorbs the nitrogen
and lets the oxygen (and argon) pass. This gives a purity of oxygen of about
93%. This works well for brazing.
Apparatus
The apparatus used in gas welding
consists basically of a torch, two pressure
regulators and twin flexible hoses. The
torch is the part that the welder holds and
manipulates to make the weld. It has two
valves and two connections, one each for
the fuel gas and the oxygen, a handle for
the welder to grasp, a mixing chamber
Two types of oxy-gas torch head

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