Strength Test After Backfilling
Strength Test After Backfilling
(OP)
I am trying to find this answer but I can't. I have been recently asked why we backfill prior to doing the strength/leak tests on a CSA pipeline. I can't recall the definitive answer but all I can remember is that is the way it is. My colleague is saying we would be able to find the leak faster if it wasn't backfilled. I did a quick search on the forums and I saw on another thread that people have said that CSA says you need to backfill first and that it "is clear". I did a quick look and all I see is that clause 8.1.3 says that the test shall be completed after the section is in place and before operation, but doesn't say anything about backfilling.





RE: Strength Test After Backfilling
The reason being that there are stresses imposed on the pipe due to soil weight and compaction and also the expansion or contraction of the pipe is different when fully restrained as opposed to being effectively un restrained at the bottom of a trench. Add in the issues about solar effects on the water temperature where a difference of a few degrees makes a big impact on test pressure and the end effect is that you backfill and complete as much of the pipeline as possible then test. Final backfill or topsoil isn't required, but the majority of the backfill is.
Strength tests are there to test the strength of the pipeline and find issues, not to leak test them. Yes if there is a leak it is difficult to locate in a buried line, but this does not create sufficient justification to not backfill as your pipeline shouldn't (and doesn't) normally leak, especially when new.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Strength Test After Backfilling
RE: Strength Test After Backfilling
Placing backfill and compacting will place loadings on the pipe. These loadings may cause leaks as well.
RE: Strength Test After Backfilling
Restrained (BURIED) Longitudinal Stress
SL = SE + ν*Pi*D/2/t + M/Z + FA/A
Unrestrained Longitudinal Stress
SL = Pi*D/4/t + i*M/Z + FA/A
longitudinal stress from pressure in an unrestrained line must include consideration of bending stress or axial stress that may be caused by elongation of the pipe due to internal pressure and result in stress at bends and at connections and produce additional loads on equipment and on supports, things not normally present, or present in much lesser extent, in buried pipe.
RE: Strength Test After Backfilling