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Wednesday, June 19, 2013

WPCT Surface Preparation

Question:  When installing WPCT shrink sleeves, how clean does the pipe have to be?

Answer:  We are always looking to get the recommended surface cleanliness ST 2 1/2 - 3.

     Sometimes this question is posed a little bit differently.  I recently had an email exchange where I was shown some photos of pipe that has been in a yard for some period of time (months).  The question was posed:  can I get these field joints to ST 2 1/2 with a wire brush after welding has been completed?

damaged pipe coating
Surface corrosion from sitting unprotected for a few months.  In addition, there has been some FBE 'lifting'.

rusty natural gas pipeline
Another view of the surface rust on this pipe that has been sitting in a yard for a few months.
     Of course, it is impossible for me to tell, based on photos, how deep this rust goes and how clean the surface will be once a power wire brush has run over it; but I think this will probably still be 'ok'.  The final determination will (of course) have to be made once an effort has been made to clean it (even running the brush over it right there in the yard would be telling). 

     If a quick power brush does not get the pipe clean; the contractor will have a couple of options.  They can put in a little bit more labor with the wire brush to get the desired cleanliness or they could skip the wire brush altogether and simply sand blast the surface clean (post weld of course). 

     But to sum up; when you're dealing with a product like Covalence's WPCT which utilizes an incredibly aggressive mastic sealant, the fact that this pipe has sat for a few months probably won't mean a darn thing.

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