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Thursday, July 25, 2013

Field Joint Coating for a 48" Pipe Road Bore

What do you do when you've got a 48" road bore and you 
are in charge of selecting the field joint coating material?  

     I recently had a call from a customer who had a real problem.  He was in charge of a directional drill involving a 48" OD pipe.  Due to some issues with the right of way; his staging area was very, very small.  He really only had enough room to weld and coat two joints of pipe at any given time.  As a result, they were going to be completing the bore in stages; pulling two joints of 48" pipe into the bore and then stopping while they welded and coated the next two joints.  After this; those two joints would go into the bore (4 total) then they would have to stop and weld/coat two more.

     This presents two major problems.  First; the starting and the stopping during the bore can put really extreme forces on the pipe; the factory applied coating and the field joint coating...especially with a 48" OD pipe!  A 48" OD pipe can weight anywhere between 190 and 250 pounds per FOOT.  That means that a 20 foot pipe joint weighs in at a whopping 3800-5000 pounds.  That is a heck of a burden for a field joint coating (or any coating) to bear! 

     The other problem is due to the minimal staging area; the contractor wasn't going to have time to wait for products to cure.  Imagine that they were using a liquid epoxy that required 16 hours to cure...they would only get two joints completed per day!! (possibly less if they ran into trouble with spray equipment / repairs / etc). 
48" Directional Drill
DIRAX shrink sleeves - even a 48" OD pipe is no problem.

     Though these are pretty significant problems for most coatings; for the DIRAX it wasn't a problem at all.  DIRAX shrink sleeves have been used on 48" pipe in the past with no problems.  It is built exactly for those kinds of incredibly challenging applications.  Beyond that; though the DIRAX shrink sleeve system does utilize a liquid epoxy (S1301M) it doesn't have the same cure times that stand alone liquid epoxy pipeline coatings experience.  Thanks to the heat put into the pipe during the preheat and thanks to the heat put into the pipe during the sleeve installation; the epoxy has been largely cured by the time installation is completed.  No long wait times; no real problems...just one more seemingly complicated directionally drilling application that DIRAX heat shrink sleeve solves with no problem!

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