Advanced Welding Processes: Technologies and Process Control

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Advanced welding processes
Procedure qualification
Formal qualification of the procedure involves completion of sample joints
to the agreed WPS, often under the supervision of the client or an independent
approval body. The welded joints are subjected to a specified selection of
non-destructive and mechanical tests, the results of which are reported in a
procedure qualification record (PQR) as shown in Fig. 10.3.
The skill of the welder is often a major factor in determining the final
weld quality. The welder’s skill may be assessed and ‘calibrated’ by means
of a general approval process. [198] It may also be required to qualify a
named welder to carry out a specific procedure.
Procedure management
Management of welding procedures using this technique involves: maintenance
of procedure specification and qualification records; calibration of welding
and ancillary equipment; and monitoring compliance with the specified
procedure.
Maintaining procedure records. Having established a satisfactory procedure
and obtained procedure qualification, it is necessary to maintain a record of
the parameters and techniques used and to control the issue of this information
to the shop floor to enable consistent joint quality to be achieved. In many
cases, this information will be required on an irregular basis particularly
when small batches of fabrications are required. The welding procedure
specification records will also be required when tendering for new projects,
when preparing procedures for new work or when analysing production
problems. A fabricator will quickly generate a large library of procedures
and it is necessary to devise a suitable system for storage and retrieval. Many
companies are now using computer database systems for procedure
management in order to reduce duplication and improve access to procedure
data. [199]
Validity of parameters and calibration of equipment. The validity of the
procedure will depend on the possibility of establishing the same operating
conditions: when the process is used with the stated parameters, by a different
operator in a different workplace using equipment and consumables of the
specified type. If the parameters specified are ambiguous or ill-defined, the
resultant weld may well be inferior to those prepared at the procedure
development stage.
For example in GMA welding when voltage is used as a control parameter,
the voltage reported should be the arc voltage measured as near to the arc as
possible. Open circuit (or no-load) values may be easier to measure, but are
meaningless unless the static characteristics of the power source are also
stated. In addition, since there may be a significant voltage drop in the