Page 205 - Welding of Aluminium and its Alloys

188 The welding of aluminium and its alloys

There is a footnote to the table in the specification that infers that, where
a multi-process procedure is used to make the joint, the approval range of
thickness of weld metal from the individual processes should be based on
the approval range given in the table.The range of approval for a fillet weld
is based on the throat thickness of the test piece and is given as 0.75a to
1.5a where a is the throat. A test piece throat thickness of 10mm or more
approves all fillet welds over 10mm throat.
An important point to remember is that a fillet weld approval provides
no information on the mechanical properties of a joint.Where the fillet weld
is to be load carrying it is necessary to perform a butt weld approval so that
tensile data are available for design purposes.
• Test piece diameter is also an essential variable when welding pipes,
tubes or hollow sections. Below 168.3mm outside diameter the approval
range is 0.5D to 2D where D is the test piece diameter. At and above
168.3mm OD the range is 0.5D to flat plates.
• Welding position has a range of approval based on the ease of making
the joint. For example, a pipe butt weld made in the vertical-up (PF)
position approves for all positions except vertical-down (PG). Similarly
there is a range of approval for joint type with an unbacked butt joint
in pipe approving for all other butt and fillet welds. For full details of
these ranges reference should be made to Tables 8 and 9 in the specifi-
cation. A sketch explaining the welding positions and how they are
designated is included as Fig. 10.3.
• Other essential variables comprise the welding process; filler metal
classification; type of current; heat input when specified; preheat and
interpass temperature; post-weld heat treatment or ageing; the type of
both shielding and backing gases; and the number of filler wires in MIG
welding.

Once the procedure is approved and the WPAR is written the approval
remains valid indefinitely provided that none of the essential variables
are changed outside of their range of approval. This approval enables any
number of welding procedures or work instructions to be written, provided
that the variables specified in the WPS are within the range of approval of
the WPAR.
While the best effort has been made to provide an accurate summary of
BS EN 288 Part 4 and the information is correct at the time of writing it is
recommended that the specification is referred to when there is a require-
ment to comply in the application standard or in contractual documents.

10.2.2 ASME IX welding and brazing qualifications

The principles of approval testing in this ASME code are very similar to
those adopted for the EN specifications.There are testing requirements for