High Density Polyethylene Pipe 4

[klyons]

I am wondering if anyone out there has any experience with HDPE pipe in natural gas gathering. The vendors tell me that it can handle wet gas with hydrocarbons and potential for freezes but I am still skeptical. Also, the fitings worry me because they seem to rely simply on clamping pressure.

Anyones experience with HDPE pipe would be greatly appreciated.

 

[zdas04]

What sizes are you looking at? 4-inch is the smallest I've run, but it was welded, not clamped.

HDPE has had good results in gas. One of my clients likes it in a freeze because it has more resilience than the expansion of water on phase change so it doesn't break in a freeze like steel often does.

David

 

[brimmer]

We use it widely in gas gathering fields in Canada with no issues (relatively speaking). Use fusion welds as opposed to clamps, most failures we experience are due to lack of structural support. With wet gas some hydrocarbon can be absorbed into pipe over time. Most codes have safety factor as far as MOP for wet service.

 

[jmiles]

I havent used pure HDPE in a while, but i ahve used composites like FlexSteel, which is HDPE with steel reinforcement, the only caution i would ahve is that from all the literature ive read gas can and will migrate through HDPE, not enough to really be a big concern, but there is enough of it that I know FlexSteel has vents so gas does not build up around the steel reinforcements between HDPE layers.

 

[klyons]

The HDPE pipe being considered is from flexpipe(

http://www.flexpipesystems.com

) we are just looking into it for our gathering system becuase of the reduced cost of construction and maintenance.

I guess a better way of phrasing my question is what the pros and cons of the HDPE pipe and what were the major problems encountered in using it (Brimmer - what kind of structural support does it require, I'm guessing a lot more than steel if that is where most of your failures came from)?

Thanks

 

[zdas04]

Ok, the most common name for the FlexSteel is "spoolable composite". When you say HDPE, people start thinking in terms of the SDR series of low pressure piping.

FlexSteel is pretty amazing stuff. It is the only spoolable composite that I've found that is certified for offshore. The connection system is quite robust and is not prone to leakage. It comes in very high pressure rating (up to ANSI 900) and it is the only high-pressure spool product I've found that comes in 6-inch. There are reports of people ploughing 4-inch in at the rate of up to 1 mile/hour (typical trenching, welding, jeeping, lowering, and backfilling of a 4-inch steel line is closer to 1/8 mile/day). You only get that kind of productivity in places without many pipeline and/or road crossings, but it goes in faster and cheaper than steel in any country (someplace like the San Juan Basin where it is rare to go a quarter mile without crossing something it takes some finesse to snake it under crossings, but it is still faster than steel).

I once put together a matrix for a client comparing steel, FuturePipe, FlexPipe, FlexSteel, Centron (stick fiber reinforced plastic), and HDPE. The details are part of a proprietary report, but the conclusion was the that spoolable composites (FuturePipe, FlexPipe, and FlexSteel) were at least an order of magnitude better than steel, stick FRP, or HDPE for almost any application that the spoolable products could serve (they only go up to 4-inch or 6-inch). Of the three that I evaluated, I liked the FlexSteel best.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

"Life is nature's way of preserving meat" The Master on Dr. Who

 

[rickfer]

I'd advise to fusion HDPE instead of campling it. It's more relieble.

HDPE is non conductive, so static may stay on HDPE pipes. And static is very dangerous when using a flammable fluid, specially if pipe is not full and some vapour may run throught it.
You'll need to ground fluid every some short distance, and be sure that fluid velocity isn't very high (about 1 m/s or less if possible).
I've heard dozens of histories of hdpe pipes carring organic solutions that exploded.

HDPE pipe is not self-supported. So you can't hang it from a support, it needs to lie on a bed.
However, you can run it overland, on the land, not over as steel pipe must be.

And, as you know, HDPE installation and maintenance is lot faster and cheaper than other options.

 

[zdas04]

rickfer,
This thread has moved beyond that discussion. The pipe he's considering is not an SDR rated HDPE, but one of the new spoolable composites. The system that FlexSteel uses is very similar to the clamping mechinism used on the Pex tubing in residential applications and has stood up to millions of hours of use in the field. You can't fusion weld FlexSteel.

David

 

[brimmer]

Klyons,

let me give you a guide that covers a range of topics related to HDPE pipe. I want to STRESS this guide is in DRAFT form only as we are currently working on it, but it give some care/handling/installation/hisotry on HDPE pipe.
Most of our failures are at riser sites or near riser sites where there has been lack of support or pipe movement over time. There will always be some ground settling after installation which could cause line breaks as well. Usually we plow spoolable line in and have had success with the brand you mention (even though I don't think we are supposed to mention brand names in the forum). Use fusion welds to join were needed. For hydrocarbon absorption, usually is not an issue until a failure in an area, then it is very difficult to fuse a new piece in place due to an "aero bar" type effect, but can remove additional pipe to tie into good pipe. Take care during installation is a good piece of advice I can give, otherwise the damage caused can fail hydrotest or fail later. Check your local codes for use of HDPE pipe.

 

[jmiles]

klyons,

I have used both FlexSteel and Flexpipe, honestly i like both products, they both work very well, but neither of them are HDPE as such, they are composite pipes as zds has pointed out, and in terms of mechanical performance theya re very different from HDPE.

The upside is you get much higher pressures. but the cost is a little more. That beng said with Flexsteel you can go up to 6" and it still comes on a spool, i believe its around 300m on a spool, which is quite respectable.

Now as for the clamping system, i cant comment on flexpipe, but i was int he field on a job using flexsteel and the end fittings as zdas has pointed out are very robust, and the bonus is if like me you want to avoid having buried flanges you can weld the end connections for FlexSteel.

I would not recommend either product for above ground installation as theya re spoolable they are not self supporting, and even laid on a bed above ground you will need to look into UV stabilization, there are versions of both products available whch ae UV stable but they cost more.

In terms of longevity and performance both products are quite good, I have ehard some comments about fiberspar degrading after it is in the ground, but from all ive been able to learn each failure could be traced abck to poor installation.

As a note, i have seen Flexsteel kinked on installation, its a simple thign to fix, 2 cuts 2 end fittings and a weld later and we were back in business, BUT those end fittings are quite expensive.

Thats your main downside to any composite pipe, the end fittings are quite costly, but they work very well.

 

[klyons]

Thank you all for your posts I really appreciate it!

zdas04 - What was your reasoning for liking the FlexSteel better?

brimmer - You said that you had used the composite pipe in gathering systems did you ever come across any problems with the junk that can get into the pipes from the producers, like some of the chemicals that they used to drill? Also, I tried to open the guide you posted but I can't get it to work (I just keep getting a blank page in explorer), would you be willing to post it again please?

jmiles - Did you use another way to connect the FlexPipe other than the clamping? How did it work?

 

[zdas04]

I'm getting on shaky ground here, but in general terms I like the connections (as opposed to FuturePipe which is like building a boat) and I REALLY like being able to find it with a line locator without having to mess with marker tape.

David

 

[jmiles]

Klyons,

I only ever used the standard fittings for flexpipe and flexsteel (with flexsteel we just cut off the flanges and did a butt weld)

I never had any issues with either connection type, BUT, i particularly liked the double compression swage fitting that FlexSteel uses, essentially they press the fitting on to the pipe from the inside and the outside, and the connection has been proven in high pressures both onshore and offshore.

Plus like Zdas mentioned, no tracer wire is required for this.

All in all though composite pipes are somethign I am very much a fan of, they work well they go in fast and easy. the conenctions in my experience are also very robust. given a choice i will always use composite pipes over HDPE, if for no other reason than the lower pressures that HDPE offers. future expansion is alot easier on a system if you can jsut spend the money opn pump HP rather than dig up a line and replace it.

 

[klyons]

Have any of you ever plowed it in with a ripper? How did that go? What were some of the main problems you encountered?

 

[jmiles]

In my experience Ploughing can work great, but it really depends on the terrain.

If by a ripper you mean the ripper from a dozer, then i have never seen it done that way....

Honestly though for myself i almost prefer to trench it in, if you have a nice flat farmers field with no big rocks or other obstacles ploughing will be very fast and easy... but then with a good operator ive seen guys trench out almost 1000m in a day with a hoe. then you add int he ffact that most of the time you have areas a plough just cant do, and well its a judgement call for sure. shorter lengths you will just want to trench it in, if you have to put in 2 km, id rather spend 2-3 days with hoes trenching that out than anywhere between 1-4 days with a plow and hoes.

 

[brimmer]

Attempted attachment again.

 

[brimmer]

Attachment not working, don't know why, I have attached other documents in this form, final attempt.

 

[klyons]

It finaly worked! Thanks a lot!