HDPE Pipe failure

[Eduardo1982]

Dear sirs.
I am facing a problem in HDPE pipe big diameter in some joints fused in Factory. When we made the hydrotest, one of these joints failed almost totally.
We are thinking if UT is possible to be performed in order to detect any internal defect.
Have you performed some NDT test on this kind of joints in the past?.. Actually some of HDPE pipe suppliers mentions that NDT like UT or RT are not possible to be performed. I would gather some opinión. Thanks!

 

[Compositepro]

I'm not aware of any NDT that would reveal any but the most glaring failures due to lack of fusion or contamination. Adhesive bonded joints have a similar issue. Careful surface preparation and process controls are required.

Here is a relevant report on a plastic gas pipe failure:

http://www.ntsb.gov/news/events/Documents/2015_Manhattan_BMG_DCA14MP002_Abstract.pdf

 

[LittleInch]

There are no NDT methods I am aware of that can be used on PE. For "factory" joints, you are reliant on the procedures being followed and quality inspections / inspectors. Ususally for fusion joints, the "NDT" can be that the external bead is removed and should remain pliable and elastic, even when bent through 180 degrees or more. If it is brittle or exhibits debri inside, then the joint is suspect.

Ask the vendor what QA he did on the joints and the physical proof ( these beads are often kept until delivery).

Pressure test is your only way of finding defcts in the joints other than cutting one apart to check for complete fusion.

This is a manufacturing defect so the action should be on the suppliers.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[austsa]

See ISO 13956. It is a destructive decohesion test.
I have seen joints passing hydrostatic but failing decohesion.
Whilst following process is very important, there are small differences between manufacturers of electrofusion fittings.

 

[brimmer]

No, you wont be able to do RT or UT on HDPE, wont work (at least UT not the best for that application). There is one technology that I am aware of and have used a little, it is very specialized and I only know of one company here in Canada that does it. It uses microwaves to detect discontinuities. Here is the link for you to find out more info if interested, called Evisive. We are now using this on some of our newer construciton HDPE lines.

http://www.spectrumndt.com/evisive.html

 

[Eduardo1982]

Hey Brimmer, thanks so much for your comments. Really I found very interesting, this kind of NDT services is rare to find available in my country (I am from south america). Have you worked with this system before? What is the new construction that you are involved in?

 

[brimmer]

That kind of NDT won't be available in South America, having worked there extensivley in the past, you would have to bring those company's that do this down on a project if you wanted to try. We have the same issues here, many of the welds on HDPE pipe have fusion issues, there is limited testing we can do (we complete specific bend tests and destructive testing on a percentage of joints, etc., but can't get them all), some fail hydrotest, or worse while the lines are in service. We are completing this type of testing on the larger HDPE projects we have (larger diameter, higher pressure lines) for better quality control. Of course, this being new, there are no acceptance standards in the code for non destrucitve methods for composite lines, so we have to make our own as well (in addition to completing destructive tests in the code).

Saludos

 

[brimmer]

Here is a paper on the topic.

 

[brimmer]

and another

 

[Eduardo1982]

Hello Brimmer, I am really disappointed. I really thought that some NDT technique could be performed in HDPE easily, but now I think that it is really complicated (considering that probably I won't get this service in South America, the one you mentioned before).. so what can I do?.. The manufacturer of these HDPE Tees probably made some mistakes at Factory and I never will know if internally on this HDPE Tees there are some defects. I am worried that only the hydrotest is the unique method to find problems. I have performed hydrotest some weeks ago and 700 cubic meters of water flooded a lot of main foundations of my Project. I am worried it can happen again, that why I am seeking for some help.
I will appreciate if someone of the gentlemen here before have faced some problems like that and would like to know final solution.

 

[brimmer]

Options without knowning all yor info/scenario may be:
Bring down an inspection company with the microwave technology and inspect
Try UT and MT and hope for the best (maybe able to detect a very large flaw, but cold fusion crack would be difficult)
Replace the joints (I don't know how many you have, may be too many) and QA/QC to the fusion process in the factory
What is the service of the pipelines? Probably the biggest concern is any defects in the welds could fail from fatigue growth in the future. If the servie is cyclical, could grow and fail in the future. If it is non-cyclical, given that the other sections have passed the hydrotest, there would be more limited opprotunity for flaw growth (need more info on service conditions to fully comment on this) and not as much concern. Also, don't know what the test pressure was in relation to the operating pressure.
Hydrotest at some frequency moving forward with contigency for a leak, this would solve the integrity issue, but obviously if flooding is the concern this might not be an option for you. Might be able to test only small sections rather than entire line to reduce volume of water????