HDPE Pipe Electrofusion 2

[jercan]

We are putting in a 30” line. Unfortunately a 36” line which has been installed on the property next to us has been experiencing problems with the Electro fusion couplings failing and this has caused us concern regarding our potential for success. Since it is not our line we have not been able to get good information on the actual reasons for the failures. Therefore we have had to investigate all possible causes of failures and then prepare mitigation plans for each one. There seems to be quite a difference between the installation of 36” lines and 30” lines due the weight difference (almost double) and the fact a long string of 36” pipe is less flexible. We are trying to minimize the number of couplings we use and we believe the flexibility may help us get there but we cannot do the job without having to use some couplings. Does anyone have any experience with 36" pipe?

 

[Apakrat]

Apparently the 36" HDPE pipe was not constructed properly.

Like steel welding, the electro fusion should be stronger than the pipe and should not weaken pipe adjacent to weld.


At 74th year working on IR-One PhD from UHK - - -

 

[jercan]

The pipe is buried at least 5’ where we are open trenching and 20’ plus where we are directional drilling placing it below the frost line. The base is made of gravel and sand layers. We have not discussed the stabilization of the pipe during burying yet. I thought maybe backfilling the pipe might have caused strain on the weld. Maybe backfilling prior to welding the electro fusion coupling in place would remedy this. Foreign material on the fusion interface could have also caused weaknesses.

 

[Stego1]

Temperature or presence of water may be a problem, especially if you're working around the frost line. Does the manufacturer's info say anything about working temperatures?

 

[StephenA]

Electro-fusion couplings at the larger sizes can be very problematic and they need very good alignment prior to activation.

If alignment tools are not used then failure often occurs. The alignment tool keeps the two pipes aligned so that good bonding occurs.

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[jercan]

What kind of alignment tools are typically used. Does this tool provide a method of measuring for alignment?

We have been butt fusing some of the welds outside the trench as well as electrofusing some in the trench.

I have been told there is a limited on how much pipe you can string together by butt fusion because the machine cannot pull. The butt fision has been going well to date.

 

[rconner]

Polyethylene material was reportedly invented in ~1933. Due to the nature of polyethylene piping and typical installation developed since, that most often depend on welds to contain pressure as well as withstand some level of direct tensile and bending stresses (and often throughout the pipelines life), the long-term performance of the piping is obviously much reliant on the welds or fusions used to join same. It is some interesting that to the present day, now 75 years later and after the input of no doubt millions of dollars of private (and maybe now also some public money?) into the effort, that there are still reportedly some problems as noted in this thread and many other places in joining of the pipe material!
I noticed for instance that the conclusions of a contemporary report of a very recent research study authored in 2008, and now available at

http://www.pnl.gov/main/publications/external/technical_reports/PNNL-17584.pdf,

essentially read not unlike many others I have read from many other sources/studies for more than a decade, “Visual testing does not seem to reveal a subtle condition like lack of fusion in a butt fusion joint. It is a surface evaluation technique and does not represent the volumetric condition of a fusion joint. Research conducted to date shows that VT only detects certain unacceptable butt fusion joint conditions. The research indicates that VT will not detect many of the conditions that should not go into service.” Paradoxically, (various descriptions of) visual examination are what has reportedly been employed/promoted by many industry folks for field joining of this pipe for many years (and may still be promoted and/or relied upon in many areas)!

Lest my criticism sound overly jaded, I will first say that I suspect all modern piping systems including e.g. hdpe, ductile iron, and all other piping obviously have some utility and when properly manufactured an installed according to all requirements will often not leak when installed. All systems likewise have problems at one time or another with the piping and/or joints. However, many plastic pipe manufacturers and e.g. also some fusing machine manufacturers and operators have however unfortunately for many years (I believe at least quite disingenuously, if not downright dangerously) promoted e.g. hdpe piping as a “jointless” pipe system. While even Engineers (I guess) allow some latitude to Marketing hyperbole, this specific wording gets some irritating when such perceptions are apparently parroted into at least a few technical and maybe even regulatory/legislative environments.

In my opinion the ramifications of the “jointless” perception could become much more significant as the pipe sizes and wall thickness increase, and systems involve more services and lateral connections etc. I have seen many difficulties over the years talked about in various forums, that obviously reveal that hdpe piping does in fact have joints and needs for lateral connections, must be connected by such, and furthermore (in a sense more or less in common to virtually all types of pipes) there can and will be some problems associated with such connections accomplished in the field.

If one somehow gets beyond all the axial and radial alignment, cleanliness/various forms of contamination, electrofusion wire location, and temperature etc. controls that are issues in the field, as well as substantial proper fusion time in particularly larger sized pipes involved in all varied field environments (and I’m not sure that’s a “gimme”), fused plastic piping has a sort of unique further/additional requirement in that a substantial “cool-down” period is required before the joint can be meaningfully moved or stressed etc. This required cool-down period (that is certainly not advertised in at least pipe marketing literature for butt or electrofused systems!) has traditionally increased as the size and maybe even thickness of pipe increase. While I of course don’t know exactly what manufacturer or thickness of pipes you are dealing with (and I am frankly even somewhat amazed electrofusion is being employed in these size pipes!) see e.g. that for just 300mm ~12” size electrofusion couplings per page 3 of the vendor information at

http://www.glynwed.se/pdf/SANITARY/AKATHERM/Installationsanvisningar.pdf

, that for more than a half hour, “The joint should not be disturbed during the fusion cycle and for the specified cooling time afterwards.” I can only imagine what the cooling time requirements would be for the much larger/thicker hdpe pipes you are dealing with, and how difficult this might be to literally obtain in an exposed piping environment, where even assuming everything else is perfect the joints of a welded pipeline might in a sense be even unintentionally stressed (or “disturbed”?) by the thermal effects of ambient temperature conditions and sunlight etc.! It appears e.g. from page 10 etc. of

http://www.cpchem.com/hb/getdocanon.asp?doc=871&lib=CPC-Portal

that one may be talking about an hour or more joining time PER JOINT under the best of conditions for even butt-joining such big hdpe pipes, and the cooling should not be hurried. Very long proper fusion and cool-down times at the very least no doubt try the patience and diligence of even very good pipeline contractors (and contemporary “bean counters”), to whom “bottom-line” construction/production rate is somewhat important.

There is incidentally some quite interesting specific wording now contained on the plastic welding website at

http://www.plasticsmag.com/ta.asp?aid=3212,

that reads as follows, “A good weld shows a perfect mixture between the molecules of the welded plastic materials.” In a world where it has been said natural processes are tending more toward some disorder than “a perfect mixture between the molecules”, it appears that definition would mean welds that may not be “good” will likely be encountered. It appears that for that reason also some other plastic pipe stakeholders are consequently now claiming insignificance in at least some exposures of some (perhaps thus far inevitable?) flaws/lack of fusion in the joints (when some are, it appears inevitably, detected by more sophisticated means than visual?) Big pipe of course has a lot more molecules to somehow get “perfectly mixed”!

If you wish to contact them, I think work involving weld and/or other fusion integrity is likely ongoing from Battelle, the Edison Welding Institute and/or others, that perhaps could be of some interest or help to you. I think a web etc. search would likely now reveal much more information.

 

[stanier]

I would be interested in the name of the manufacturer of such large electro-fusion couplings. Up to now I have only seen DN500.

Was the material HDPE or MDPE?

Generally any failures of electro-fusion couplings occur because the surface of the PE has not been prepared in accordance with the manufacturers instructions. The surce of the PE has to be "peeled" to remove any lubricants used the manufacture of the pipe. With a butt fusion weld the surface is of virgin material.

As for the alarmist view that PE cannot be joined without a "joint" there exists evidence of ocean outfalls, pipelines and many gas distribution networks successfully constructed in PE.

That said any pipe system will fail if not constructed properly. One ductile iron pipeline I examined required eleven attempts to meet the hydrotest successfully. All because the contractor wa slack and did not fit the rubber ring gaskets correctly.

Faulty welds in steel, stainless steel, lack of pickling and passivation in super duplex and other events can all bring a pipeline undone.

 

[StephenA]

This company makes large size EF couplings

http://tegaelectrofusion.com/

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[rconner]

stanier, there may be a fine line between “alarmist” and many parties knowing, as least as much as possible upfront, basically about what their getting into with regard to piping materials. You have mentioned that, “The sur(fa)ce of the PE has to be "peeled" to remove any lubricants used the manufacture of the pipe.” I suspect that whatever is involved in that operation you describe would become some move difficult to achieve with any degree of effectiveness and with (electrofusion of) large pipes in field circumstances, due to the areas and shapes etc. involved. Even if one is somehow able and willing (diligent) to effectively prepare the surfaces as you suggest, there are reportedly even further potential sources of contamination/concern. The site at

http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc45337/nrcc45337.pdf

for example explains that,

“The quality of fused test joints was adversely affected by dust contamination.” (“dust” referring to apparently soil or cement dust etc. the researchers chose to look at, I suspect due to prevalence on all or many construction sites). And even,

“Dust can be attracted to the heater plate as well as to the welding surfaces during a fusion process, and trapped dust will affect the quality of the joint.” (though whatever attraction mechanism they discovered is not elaborated on).

Pg 57 of the manual at

http://www.isco-pipe.com/pdf/English Fusion Manual Version 3.1 2006.pdf

and other references explains also that the many causes of electrofusion defects also include “hydrocarbon contamination” [though it is not explained exactly how this is dependably detected prior to fusing, nor eliminated if that is possible (directly on the surface and/or infused due to contact with liquid fuel or waste, chainsaw bar oil, or fuel etc. fumes) in shipped/stored or underground pipes.

The site

http://www.wlplastics.com/pdf/WL101 0508 Field Procedures.pdf

e.g. now also includes the caveat,
“Liquid Hydrocarbon Permeated Pipe
Liquid hydrocarbons such as crude oil, gasoline, kerosene, fuel oil, natural gas condensates and the like that are in the pipe or in surrounding soil will permeate into the pipe wall. Liquid hydrocarbon permeation generally has a minor effect on pipe that is already installed and joined. However, weak, unreliable joints can result when heat fusion is used to join polyolefin piping that has been permeated with liquid hydrocarbons.
In the field, liquid hydrocarbon permeation is indicated by a bubbly or pock-marked surface when the heating tool is removed during fusion joining. In some instances, the odor of the liquid hydrocarbon from the pipe or the surrounding soil or an enlarged pipe OD can be an indication.
Research indicates that joints made using pipes having moderate to higher levels of liquid hydrocarbon permeation will be unreliable, low-strength fusion joints. Low levels of liquid hydrocarbon permeation may not be as deleterious, but there are no quick field tests to determine the actual level of permeation…”

Perhaps as a by-product of the industrial or automobile etc. ages and particularly in developed countries, I understand there is a surprising amount of contaminated or potentially contaminated soil area into which pipelines are or must be installed. Present and future abilities to dependably connect end-wise and laterally to such pipelines is perhaps not a trivial matter. When the finished product is potable water delivery, “permeation” is an even further concern.

[Incidentally, whether or not a push-on gasket has been “fitted” properly in a ductile iron pipe joint can normally be detected in a few seconds check around the joint right after it is put together with a common blade-type feeler gauge, before the pipe is covered up. This should minimize testing iterations required.]

 

[stanier]

rconner,

I appreciate your insight into the "negatives" associated with a product. It would be pleasing on day to see a more balance view where the "positives" are also expressed.

If you are professionally associated with DIPRA or other marketing organization it would also benefit readers to know. For views to be so positive about ductile iron and nothing else I can only assume that this is the case. It is tantamount to unpaid advertising.

If it walks like a duck and quacks like a duck, it is a duck.

 

[rconner]

stanier, the initial request on this thread included to "investigate all possible causes of failures" for some joint fusions of large diameter hdpe pipes. I will apologize to all if information in my posts and references I have provided has not addressed these issues, or has otherwise not been technically correct. Please let me know of the latter, as the last thing I want to do is provide incorrect information.
While I do not believe specific identification as you have unilaterally asked of me is necessarily encouraged on these lists, I don't think I am "hard to find". In the course of my job, I have however over many years been asked frequently about and even tested many different types of pipe, including polyethylene, and I try to "keep up" with as much as I can).
Why do you however, repeatedly in this and other threads, appear to make attempts of diversion or ad hominem/discrediting the messenger (and in so doing the veracity or relevance of the message), it appears by other means than addressing the technical issues? I believe DIPRA is an honorable organization. If that somehow affects my credibility with you or others, so be it.
I did read that someone else introduced a negative into this thread that did not address the pipe/subject of the original post, and it was not me.

 

[stanier]

rconner,

Please forgive me as I am not discrediting the technical merit of what you bring to this thread and others. In fact I have on a number of occasions agreed whole heartedly with your sentiments.

It does appear that there is a conflict of interest where your postings are so biased towards one product and negative towards others without your signing off as a representative of DIPRA. For those reading the posting without this knowledge they are at a disadvantage.

So perhaps you could add your full title to your position so that everyone is aware of the thrust of the arguments being put. After all you are using an open forum to promote your products,. A very cost effective form of marketing.

 

[rconner]

stanier, it is my understanding posting of personal information is forbidden on this forum. I further believe the continued vibrance of any forum similar to this probably includes at least a couple different factors, one of course being the quality and amount of information/references provided, but another could quite conceivably be assuring anonymity of posts.
I have contributed to and learned from many forums that have come and gone over the years, some of which have unlike this forum required personal information/titles etc. to be included with each post. While it is my observation that for whatever reasons some of the latter type have withered on the vine, it is interesting that this forum on the other hand continues over many years to be replete with a lot of posts/information from huge numbers of folks. This is quite likely no accident, and I think a credit to the administrators. I compose my posts here just like I did/would any other, and much of the effort is accomplished on my own time. I do not speak for my employer, nor DIPRA.
There is much information and many references provided in these forums (some accurate and some inaccurate, with the latter it appears normally being quite quickly weeded out by the many knowledgeable members) that can additionally be readily searched by members with keywords to develop their own opinions, and it is one of the most vibrant forums I have seen. I believe accurate information concerning all piping materials and other subjects will ultimately benefit tax/rate payers (of which I “are” one), other Owners of pipelines etc., and the public in general.
If you believe anyone is somehow unqualified to post to this forum, or in general have engaged in any activities that are not in keeping with the spirit of same, you are certainly free as long as you are a member to red flag the post for appropriate investigation. While I have not agreed with all posts/posters I have personally not used that mechanism myself, as I’m not sure altruism, censorship or otherwise attempting to stifle opinions has historically worked very well. I would rather discuss technical issues and invite input from all.

 

[stanier]

rconner,
Thank you for the invite. If you care not to divulge who you represent then I will red flag your postings.