|
Welding Procedures, WHY?
 The basic requirement of a weld is to be equal to the material it is joining; the designer selects the material specification and thickness based on the anticipated operating conditions. If for some reason the weld is not equal, then it is the weak link. Worse still there is no way of knowing how much weaker it is than the parent material.
Procedure Qualifications are documentary evidence the weld equals the parent material and that welds are repeatable for production. The WPS (weld procedure specification) tells the welder what he must do (for repeatability) and it tells the client what his supplier intends to do. Therefore the fabricator must look at the most productive way of making his production welds and complete the weld qualification in the same way.
Quality Assurance is the planning aspect of quality, in a major structure there are many steps.
From the welders position the steps are, but not limited to:-
- Steel Manufacture & Testing
The designer must know the properties of the selected steel are consistent. The public get their assurance from the designer.
- Electrode Manufacture & Testing
The welder and manufacturer must know the consumable will do what is required
- Weld Procedure Qualification & Testing
The manufacturer must know what combination of events will produce satisfactory welds, 'see essential variables'
- Welder Qualification & Testing
The welder must be confident what he is doing is correct
- Laboratories Perform Mechanical Tests
They and their equipment have to be tested on a regular basis. (Even the testers have to be tested) All proceeding is a waste of time if the laboratory technician does not know what is required or his equipment is inaccurate.
Notice nothing is assumed to be OK, it is tested.
If any of the steps have a problem, the whole structure has a problem! |