One of the toughest tasks of a project manger is making the decision upon the PQR requirements for the entire project. He should be able to select the minimum number of test coupons to be qualified to cover the entire range of material and thickness.
The decision is done considering the thickness, process, electrode/filler wire and the material used in the project.
Material
The first step for the decision of PQR starts with the listing of materials in that project. This can be obtained from drawings, Line index chart (In case of piping), project documents etc.
Thickness
The second step for the decision of PQR requires the highest and lowest thickness of each material in that project. This can be decided by the review of drawings, Line schedule chart/line index chart (In case of piping), project documents etc.
Based on the lowest and highest thickness, by referring QW 451.1. The thickness range qualified by PQR decides what are the thickness of test coupo are to be made for a particular metal for qualifying the entire thickness range.
Please refer http://hareeshkv.blogspot.com/2015/06/asme-section-ix.html for details on how this is done.
Process
The third step for the decision of PQR requires the decision of which welding process is to be adopted.
For a small thickness joint normally GTAW welding is preferred. (Not necessary but this gives a good defect free joint in most cases.) This decision is also done based on the material being welded. Suppose the material is Stainless Steel (SS) or Alloy Steel (AS) GTAW is done and if it is Carbon Steel (CS) SMAW welding is done. (These are normal cases and does not contain any rules)
For thicker joints SMAW welding will be done. In this case also if, more productivity is needed FCAW/GMAW etc will be used
For very higher thickness joints SAW/FCAW/GMAW welding will be preferred as those process are highly productive.
Electrode/Filler Wire
The fourth and final step for the decision of PQR requires the decision of which welding electrode/filler wire to be used.
There are many cases where there are options in choosing a electrode/filler wire for a particular process.
Example: For the welding of a CS material we can use E6013 or E7018 in SMAW welding.
If these all are decided we can start the process of making a weld coupon for PQR.
Examples of this will be given in the next post.
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