High pressure poly 1

[mch22112]

Hi,
Is anyone aware of a poly pipe product that is suitable for approx. 26 barg design pressure in 24" (natural gas service)? It's off the charts for the usual products, but perhaps there is a more advanced product that I'm not aware of.
Thanks

 

[LittleInch]

Have a look at UHMW PE. Goes to 20bar at 16" for sure, but you might get 24 but not for a 50 year life.

A lot of the fibre reinforced stuff goes up to 26 and beyond, but PE will just end up too thick.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[zdas04]

Have you looked at putting steel pipe in the ground and pulling a HDPE liner through it? I did an 8" job using United Pipeline Systems a couple of years ago and was really impressed with the product in an old, horribly designed system. With new pipe it would be a piece of cake to weld up 20-30 joints of 24", lower it in the ditch, then pull the liner and backfill. Adding the liner to Sched 5 pipe increased the system MAWP from something around 400 psig to greater than the ANSI 600 flange ratings. The only real downside is the limited pull length of the liner, and you have to weld flanges on your steel at the limits of the pull length. Some people hate buried flanges. I never really understood why. If you have to have MAWP of at least 26 barg, I don't think that there is a more cost-effective way to provide corrosion resistance.

The 20 barg product that LittleInch mentioned has that rating at 23 C in clean water. Any other product or higher temperatures drops that number quickly.

If you have a legitimate need for poly and for your pressure rating and for the pipe size, don't screw around with half solutions. Using SDR-7, you would need to go to a 36 inch nominal product in HDPE to get 24 inch ID.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[mch22112]

Thanks LittleInch and zd, some good advice there. After further investigation it looks like the normal poly solutions won't do the job. The lining idea is a possibility. I was aware of that option, but it's a little tricky because there are many closely spaced bends on this pipeline. So we would end up with a lot of flanged joints as you mentioned. Perhaps a GRE piping system could be used?

 

[brimmer]

I believe you might find GRE pipe to match your requirements. I haved used some GRE in above ground higher pressure brine applications, I believe it was to 25 bar. I can't comment on gas application. It was a company called Fiberglass Solutions.

 

[rconner]

At least in the USA, I believe there are actually federal pressure as well as temperature limitations regarding the use of plastic pipe (in the Code of Federal Regulations Section 192.123 at

http://cfr.regstoday.com/49cfr192.aspx#49_CFR_192p59),

that would appear to be exceeded in this case. There could very well be good reasons for some limitations (in accord with LittleInch's tag line).

 

[LittleInch]

Depends what it is you're transporting exactly. You say natural gas, but are you worried about internal or external corrosion? Liner systems can be great but be aware of gas and hydrocarbon leakage into the annulus which can collapse the liner if you depressurise the main pipe. Also makes it very difficult to run inspection pigs to check the condition of the steel pipe. You can groove the liner and then periodically release the gas in the grooves, but this is a real pain. At 26" you're kind of limited with FRP and GRE makes great piping, but has real issues with buried pipeline. It's getting better, but is no cheaper than steel so unless you have severe corrosion issues I wouldn't recommend you go down this route.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

Lining = HEADACHES HEADACHES HEADACHES HEADACHES HEADACHES HEADACHES HEADACHES HEADACHES

Independent events are seldomly independent.

 

[zdas04]

The liners that I referenced above are grooved, and the manufacturer recommends (requires, their recommendation was pretty strong) that you have tap at every flange to vent the annulus. We jumpered the flanges and just put vents at doglegs. Seems to be working well and I was quite happy with the results.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[LittleInch]

In the right location and knowing all the issues, liners can be a great way on extending a pipe life or designing for corrosive fluid, but they're not without issues. So long as you know them then you can make an informed decision.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mch22112]

Thanks guys. It's a wet, sour gas, so internal corrosion in the big issue. CRA (clad / lined) is an obvious solution, but it's very expensive and the lead time for purchase (of a few miles) is more than 12 months at the moment. I was hoping for a short lead time alternative (and cheaper would be a bonus). As I mentioned, there are a lot of bends in the line, so a poly liner is a little messy, but I'll certainly give it some consideration.

 

[BigInch]

Don't plan on finishing that job on time or under budget. The ropes too short. The flanges too far apart. Pull load too much for the skinny rope they brought along. Winch doesn't have enough capacity. I've heard them all.

Independent events are seldomly independent.