Saturday, December 13, 2014

Repair WPS

When codes refer to a company having a "repair WPS", are they saying that a different test needs to be qualified other than the procedures that have already been qualified?
If this is the case, would you record the NDE, hold points, etc. that are required in the WPS? Sort of like, these are the steps and sequence of events that are required to take place.
Timothy C. CWI, CWE

P.S, Thanks for the time you've taken over the years to let us ask, argue, talk through, and debate all the issues we come across. It only makes us better at what we do.

And all this time I thought I was the only one that would get up at 6am on a Saturday with welding on the brain (I happened to be calibrating my UT scope when I got your email).
Let me concentrate on your first question as it would relate to AWS D1.1 (because you are right, the Bridge Code is more specific).
D1.1 requires a repair WPS, why would they state that? 
In most manufacturing environments we would have specific WPS’s for specific joint configurations, materials, positions welded… Let’s imagine the company "PWC Weld-All" had WPS's for all position, unlimited thickness, Base Metal Group 1 & 2 for Lap, T- (fillets & grooves), V-, Bevel and Square Groove Joints.  Your first impression would be that PWC has his shit together, right?  Now let's say PWC hired his brother (because his Mom made him) to punch bolt holes in steel with an Iron Worker.  Who could mess that up?  Well, his brother did and now you’ve got four 1- inch holes in the web of a S24x100 I-Beam.  The customer insists they be filled.  Which WPS will cover this repair?  Since the joint configuration now is a hole in a plate none of the existing WPS's will apply.  A new WPS will need to be developed which may or may not require testing (dependent on code requirements).
Here's another scenario… The base plate of a light pole tower is welded using FCAW-G.  While being erected the customers inspector finds unacceptable porosity and requires a repair.  That repair could be made using the same procedure used to manufacture the tower, but it wouldn’t be practical to use FCAW-G, in the field.  A procedure would need to be written (and possibly qualified) to complete this repair using another process (FCAW-S or SMAW). 
One last scenario… A crack in a weld is discovered in a Bevel-Groove.  The engineer determines it can be repaired.  This can typically be done using the original WPS.  While excavating you find this crack extends into base material.  Now your joint configuration will probably be outside the tolerances of your WPS, so another WPS will need to be written (and possibly qualified).
Often times the PQR's you've previously completed will cover the repair WPS, but you still need to write the new WPS. 
As the engineer I have written many repair WPS's.  When I do I will put language in there that is not typically found in a production WPS.  Things like, “Drill a X/X diameter hole at each tip of the crack to reduce the chances of growth.”  or, “Once  discontinuity is removed PT to insure its complete removal.” or, “MT each weld layer to insure soundness.” or “Never let my brother touch that machine again.”
So your repair WPS isn't anything different then any other WPS, you just want to insure that you've covered all your bases in regard to material, joint configuration, position before moving forward with the repair.

Ask me the time and I build you a watch.  Sorry about that.


1 comment:

Dash Inspectorate said...

Hey Buddy, Thanks for the information. Welding is a question of technology, but it is also a problem of mathematics. Glad you've laid it out as that.
Dash Inspectorate