BS EN 50504:2009 pdf download
BS EN 50504:2009 pdf download.Validation of arc welding equipment.
Arithmetic mean analogue instruments measure the average or mean value of the instantaneous parameter with respect to time. r.m.s. analogue instruments give an indicated rather than a true r.m.s. reading, see 9.3.
Digital meters may give true or indicated r.m.s. readings. For some equipment a single digital meter may be used to measure a.c. and d.c. voltage and current. Expert knowledge may be required to validate such equipment and the manufacturer should be consulted.
The standard methods of measurement are as follows:
a) d.c. welding supplies shall be measured with averaging techniques;
b) ac. supplies shall be measured with root mean square methods using true r.m.s. meters or using indicated r.m.s. meters (i.e. assuming pure sinusoidal form).
NOTE For power sources with non-slnusodaI wavetorma e.g. square waves, averaging techniques may be used and lb. manutacturer should be consulted (see 93)
8.2 Manual metal arc welding with covered electrodes
Manual metal arc (MMA) power sources have a constant current characteristic with a.c. or d.c. output. The current control if marked in absolute units should be validated at conventional load voltages. An arbitrarily marked scale should be checked for consistenCy.
The MMA process is often controlled by measurement of run-out length where measurement of welding Current is not necessary. However, if accurate measurement of the welding current Is required It Is preferable to use a calibrated ammeter (fitted to the power source or separate), or to use independent monitoring equipment.
MMA power sources do not have voltage controls but could be fitted with voltmeters, which can be calibrated.
8.3 Tungsten inert gas
Tungsten inert gas (TIG) power sources have a constant current characteristic with a.c. or dc. output. ‘The current control should be marked in absolute units and can be validated at conventional load voltages. Generally, TIG power sources are fitted with ammeters and possibly voltmeters, which can be calibrated. TIG power sources do not have voltage controls
TIG welding power sources are used in complex TIG welding systems and it may be required to validate the system with load conditions, which closely duplicate the arc load conditions. The resistance of the load Is calculated for a specific welding condition using the welding current and the arc voltage at that current. The welding conditions could be taken from the welding procedure. Alternatively, a stable arc may be used with a mechanically held torch with or without arc voltage control.
CAUTION Care should be taken to ensure damage does not occur to instrumentation. See Annex D for recommended precautions.
A validation method for pulsed TIG power sources is recommended in Annex C.
If accurate measurement of the welding current and voltage is required it is preferable to use an ammeter and voltmeter (fitted to the power source or separate) which can be calibrated or to use independent monitoring equipment.
CAUTION Do not shorl.c.rcult the output of a constant voltage power source as a very high current will flow; use a load resistor.
For synergically controlled and pulsed MPG power sources, a validation method is recommended in Annex C.
8.5 Auxiliary components
For validation of auxiliary components see Annex E.
9 Validation techniques
9.1 General
It is recognized that manufacturers have developed many specialized methods of validating their welding equipment that may require detailed knowledge of the construction or access to the interior of the equipment. The validation methods described in this European Standard are intended to enable the user to check that the equipment is fit for the intended purpose without the manufacturers specialist knowledge. However, some of the methods of measurement described may require specialist knowledge or apparatus.
9.2 Safety precautions
The validator should observe all normal welding safety precautions. Welding equipment should be installed and used In accordance with CLC)TS 62081. II a TIG power source Is being validated using a welding arc as a power source load, protective clothing and eye protection should be worn.
The validator should pay particular attention to safety earthing recommendations, Special attention should be given to the connection of measuring instruments and the welding current circuit to prevent high current passing through the instruments.
