Welding
Non-Ferrous
Metals
Treating
Welding
Cast Iron
Welding
Ferrous
Metals
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TESTING AND INSPECTING
Whenever materials are manufactured
some procedure has to be established to determine whether the
manufactured material or part meets
the requirements that have been established. In the steel mill, samples are
taken periodically from the furnace
and checked to make sure that the chemical analysis of the steel is correct.
After the ingots have been cast and
are being rolled, they are visually examined to determine whether there are
cracks or other defects present, and
any defects found are removed before the work progresses. In the foundry
and forge shop, the manufactured articles
are examined to make sure that there are no holes in them and that they
are of the size required. In the machine
shop parts are gauged or otherwise measured to make sure that they are
of the right dimensions.
The completeness of any testing program
and the carefulness of the inspection will depend naturally upon the
requirements. It is obviously useless
to use micrometer calipers on a part that is being rough-forged, and it is
equally useless to check the measurements
of an airplane motor cylinder with a foot rule. In the same way, it is a
waste of effort to X-ray all the welds
in a clothes locker; yet serious difficulty could occur if nothing were known
about the corrosion resistance of the
welds in a chemical piping system. Factor
of Safety A part
obviously need be no better than demanded by the requirements of service. It is
important, however, that every
service condition that is likely to be encountered be taken into consideration
in the planning. A tent made out of
ordinary cloth is sufficiently good to keep off the night dew, but if one expects
to stay dry in a rainstorm, the cloth of
the tent must be waterproof and a trench must be provided around the tent to make
certain the water does not flow
in underneath. If the rain is to be accompanied by a strong wind, the tent must
be erected substantially enough
not be blown over, an event that would make all the other precautions useless.
