Page 199 - Welding of Aluminium and its Alloys

182 The welding of aluminium and its alloys

inspection methods. The purpose of the WPS is to ensure that acceptance
criteria can be met consistently, including mechanical properties and defect
levels. It is also useful in enforcing quality control procedures, in standard-
ising on welding methods,production times and costs and in controlling pro-
duction schedules. Its prime purpose, however, is to give the welder clear,
unequivocal instructions on how a weld is to be made. A typical WPS is
shown in Fig. 10.1.
In order to confirm that the welding procedure, if followed, is capable
of providing the required strength and freedom from defects, the WPS is
approved or qualified. This approval is achieved by welding and testing
a test piece representative of the production welds, the welding details
and the test results being recorded in a weld procedure approval record
(WPAR). In the American ASME specifications this is known as a proce-
dure qualification record (PQR). Within the WPAR a number of essential
variables are identified. These essential variables are those features of the
procedure that, if changed outside a range of approval, will result in an
unacceptable change in the mechanical properties or defect level of the
weld, invalidating the WPS and making re-approval necessary.
The procedure approval specifications detail the acceptable forms of test
pieces, the essential variables and their ranges of approval, test methods
and acceptance standards. The most commonly encountered specifications
are the European specifications, the EN 288 series and the American
specifications, the ASME codes.

10.2.1 The BS EN 288 specifications for arc
welding approval
The EN series are all entitled ‘Specification and Approval of Welding
Procedures for Metallic Materials’.
There are currently 9 parts of the EN specifications as follows:
• Part 1 General Rules for Fusion Welding.
• Part 2 Welding Procedure Specification for Arc Welding.
• Part 3 Welding Procedure Tests for the Arc Welding of Steel.
• Part 4 Welding Procedure Tests for the Arc Welding of Aluminium and
its Alloys.
• Part 5 Welding Approval by Using Approved Welding Consumables for
Arc Welding.
• Part 6 Approval Related to Previous Experience.
• Part 7 Approval by a Standard Welding Procedure for Arc Welding.
• Part 8 Approval by a Pre-production Welding Test.
• Part 9 Welding Procedure Test for Pipeline Welding on Land and Off-
shore Site Butt Welding of Transmission Pipelines.