42" RCP Joint Testing Issues 2

[Jeoku]

Performing a joint test on a 42" RCP in the field is giving issues where the water is leaking out of the pipe from the inside of the pipe. Basically the water is traveling along the reinforcement inside of the pipe and finding small voids to come out of. So far there has been no water found leaking from the outside but I have concerns that the testing isn't working properly due to the leaking water.

My questions are:
1. Is there some kind of general requirements that the manufacturer is not meeting that is causing this issue?
2. What kind of manufacturing requirements are there at the joints to prevent water from piping along the reinforcement so the RCP can be tested properly?

 

[bimr]

Two tests required in the specifications are the hydrostatic pressure tests of concrete pipe in straight alignment and maximum deflected positions. The straight alignment hydrostatic test requires no leakage for 10 minutes at an internal pressure of 13 psi (30 ft.). The maximum deflected position hydrostatic test requires no leakage for 10 minutes at an internal pressure of 10 psi (23 ft.).

The tests are done periodically. Each individual pipe is not hydrostatic tested.

Sounds like poor quality control by the manufacturer.

 

[Jeoku]

If in the shop they seal the 2 pipes at the ends for their tests they would miss the problem we are having. I will have to ask them about their testing procedures to see if this is the case. Regardless if they use a regulator to manta in the pressure in the shop would a small amount of internal leakage as discussed constitute a failure?

 

[bimr]

I believe the test consists of 3 sections of the pipe joined together.

http://www.concrete-pipe.org/pdf/2007-11-Concrete-Pipe-101.pdf

If there is any leakage, the material should fail the test.

 

[rconner]

While not commenting on this particular pipe the standard specifications for some types of modern pipes nowadays are couched in sort of weasel-wording terms that may make some readers believe each/all individual pipe(s) or joints is(are) meaningfully hydrostatically or otherwise tested before it leaves the factory, when in fact that may not now be the case. Hydrostatic testing has always had a cost associated with it, made up of the massive equipment and maintenance by which it is accomplished, hands involved in the processes, as well as dealing with and treating etc large amounts of water required particularly for large diameter pipes (all arguably significant drivers, along with a competitive marketplace, to tempt folks away from same). Nevertheless, and while no sort of pipe nor testing is perfect, individual high-pressure hydrostatic testing of pipes at the factory (before they are tested in the field) has traditionally been a valuable "inspector".
In any case, it sounds as though the manufacture of this pipe may have resulted in some unintended voids or honeycombing, including where the concrete has not flowed or been vibrated around and to intimately embed the reinforcement cage (while leakage and inflow in the modern world is generally not good, I guess this may not be all that unusual for at least non-cylinder pipes?)

 

[Jeoku]

There is quite a bit of honeycombing on these pipes but I would expect that this is because a dry cast 36" diameter class IV RCP is difficult to get good consolidation.

It turns out on this particular project there was a mistake by the manufacturer as they usually provide a watertight coating on pipes that undergo field joint testing to allow the joint to be tested without the internal leak that was being experienced. These pipes were supposed to have it but somehow they missed it.

 

[dicksewerrat]

Probably a good thing. Now all the pipe made that week can be sent back to the plant for demolition.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com