Page 143 - Quick Guide to Welding and Weld Inspection by S.E. Hughes, Clifford Matthews

Health and Safety

An example would be a welding machine that can operate at
350 amps at a 60% duty cycle but only 300 amps at a 100%
duty cycle.
Do not confuse a duty cycle with a welding process’s
operating factor. They are often confused because both are
given as a percentage. A process operating factor is multiplied
by its deposition rate in economic calculations to calculate
welding costs including process down time. The down time is
the time when an arc is not struck and no welding is taking
place.
Some typical process operating factors are:
. MMA: 30%;
. MIG/MAG: 60% (hence the possible confusion with a
duty cycle);
. MIG/MAG mechanised/automated: 90%.
Remember that the operating factor percentage refers to the
percentage of time that an arc is struck.
Welding/cutting process safety
The safety considerations required for cutting and welding
operations are there to ensure:
. Suitable ventilation and extraction is in place and
operating correctly.
. There are no combustible materials such as oily rags in the
area.
. Confined spaces are gas and fume free with gas free
certificates in place.
. PPE is worn at all times.
. Permits to work are in place and complied with.
. Oil and grease is kept away from oxygen gauges and
fittings (it can ignite).
. Fittings with a high copper content are not used with
acetylene gas systems because explosive copper acetylyde
can be formed.

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Woodhead Publishing Ltd – A Quick Guide to Welding and Weld Inspection
Data Standards Ltd, Frome, Somerset – 17/9/200909QG Welding chap9.3d Page 127 of 134