approved weld procedure specifications

Approved weld procedure specifications:

For vertical tank construction and repairs and pipeline construction andrepairs a weld procedure specification is required.

This is to ensure:- weldability of the existing steel (ie the existing steel is an unknown!)- compatibility of the filler material (ie how will the joint mechanically

perform?)

Also there is a need to exercise a degree of control (the degree depends onjudgement) of how all the above has occurred.

This note will refer mainly to tank repairs, but pipelines and piping will bediscussed briefly.

For vertical tanks built to API 650 and repaired in accordance with API 653, itis stated in these documents that welding is to be in accordance with sectionIX of the ASME Boiler and Pressure Vessel Code (often called ASME 9).Australian standard AS 3992 is very similar and I consider, in the interim,should be accepted in lieu. However I would like to investigate this further.

For piping (ie inside the Terminal) weld procedures should be to AS 4041.For pipelines (ie outside the Terminal) weld procedures should be to AS2995.2

Note the terminology and the meaning. (Note the below is to aidunderstanding, not to overwrite what is in the respective standards)

Weld procedure specification. This is how the weld is to be undertaken,describing all the essential variables and the limits that this technique can beused for. If testing of the specification is required, this will have beenperformed using a welding procedure test (recorded in a procedurequalification record PQR or weld procedure qualification record WPQR).The PQR number is recorded on the WPQ.

Welder qualification test. A documented test undertaken by a weldingperson to a weld procedure specification.

However note there are certain parameters when mechanical testing is notrequired. A whole variety of parameters needs to be obeyed, but oneexample is wall thickness between 3mm and 13mm (AS 3992). Thedocumentation, however is still necessary. AS 3992 calls this “pre-qualifiedwelding procedure specifications”. ASME IX calls this “standard weldprocedure specification”s. ASME IX does not allow a “standard weldprocedure specification” to be used for welds that may be subject to brittlefracture. Brittle fracture is dealt with in API 650 and relies on thickness andtemperature.

So it may be possible that some of the repairs are covered by “pre-qualifiedwelding procedure specifications” or “standard weld procedure specifications”.

However, regardless, the WPS must be documented, and the tank materialmust be checked to see that it conforms with the WPS. (eg check for carbonequivalent. Spark testing techniques by various NDT firms may beappropriate.

I attach some extracts from standards, that illustrate the points. Theseextracts do not substitute for viewing the entire standards.

Barry Clearwater23 June 2003