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High Pressure CO2 Pipeline Valves

High Pressure CO2 Pipeline Valves

High Pressure CO2 Pipeline Valves

I need to spec out some high pressure ball valves for dry CO2 injection (between 1000 and 3000 psig) and was wondering about trim.

No prior experience with high pressure CO2 per se but after researching, I'm thinking electroless nickel on carbon steel for the ball and stem (since the service is relatively benign) with nylon seats but then I'm kind of stuck on the body seals. The typical Buna-N and Viton materials aren't compatible with CO2 (rapid depressurization issues) and beyond that it isn't clear from the manufacturer's literature what alternatives might be commonly available. Everyone seems to have a "proprietary" reference in their catalogues.

1. Any thoughts on seals that are commonly available and suitable for this application - dry high pressure CO2.

2. In a wet high pressure CO2 application (say Water alternating with CO2) I would switch to 316 SS for bodies and trim but would I need different elastomers ?

I guess my alternative would be to leave it open ended with a requirement that the elastomer be qualified to some acceptable test standard (NORSOK M-701, Shell, John Walker, etc.).

RE: High Pressure CO2 Pipeline Valves

I am probably not the best adviser here, and the answer would anyway be depending on size. For larger sizes one would probably tend to search for 'cheaper' material and sealing combinations than for lower sizes.

If you are discussing lower sizes the answer would probably be more self-evident: straight stainless steel or better qualities with PTFE, which would be adequate also with impurities, water added or acids formed. Why should it be very different for larger sizes, except for cost/lifetime reasons?

As a preliminary resarch for market availabillity I would have asked for a sample price or budget price for typical size and quantity (for further qualification before final bid) from two or several local suppliers, aiming for higher quality (25 year lifetime expected)  with option to also offer for cheaper quality /lower lifetime expectations.

RE: High Pressure CO2 Pipeline Valves

Your starting material for consideration would have to be a perfluoroelastomer with Aflas probably forming the baseline. The problem will be getting them to go to low temperatures. In any case, you are right to demand some form of validated test data showing ageing behaviour and RGD resistance in CO2 under comparable operating conditions.

Steve Jones
Materials & Corrosion Engineer

RE: High Pressure CO2 Pipeline Valves

There seems to be a proliferation of proprietary Vitons and Hydrogenated Nitriles quoted as being suitable for ED / RGD service.

- Grove talks about a 652/653 "fluoropolymer material" that they say is resistant to ED / RGD. Temp range +20 to 350 F.
- Parker talks about their compound V1238-95 "fluorocarbon material" that they claim is resistant to ED / RGD. Not sure on the Temp range.
- James Walker has some "fluoroelastomer FKM based products" including FR25/90 and FR58/90 which are tested to a variety of standards for ED / RGD.  FR25/90 is listed as -41 to 200 C and FR58/90 is listed as -27 to 210 C.  They also have a hydrogenated nitrile material "Elast-O-Lion 101" which is rated -29 to 160 C for ED / RGD and "Elast-O-Lion 985" rated -55 to 150 C.

Does anyone have specific experience with any of these or others in a dense phase CO2 injection system?  

Alfas would be a consideration but with ambient temperatures reach between -29 and -46 C, it really doesn't have acceptable low temperature performance for the application.


RE: High Pressure CO2 Pipeline Valves

I had an Engineer with PBV show me an o-ring that had come out of one of his valves in dense phase CO2 service (i.e., above 87.76F and 1070 psia).  The o-ring had thousands of "trap doors" in the material.  His explaination was that the Dense Phase CO2 collected within the elastomer and when the line was depressurized the CO2 expanded back to normal gas phase and ripped the o-ring up.  He said that every elastomer on the valve was similarly damaged.  He had a materials fix (this was around 1995), but that the stuff was kind of hard to get.

I would contact the valve vendor with your operating conditions and see what they say about those specific conditions.  If they say "we have a fix" then they probably do.  If they say "CO2 is no problem" then they probably don't know what problems are possible.


RE: High Pressure CO2 Pipeline Valves

Get the suppliers to walk the talk and put the qualification test reports on your desk.  My experience with hydrocarbon-CO2-H2S is that when you put these wonderful supplier recommendations to the test, some of them tend to fail (badly!).

-46 deg C and RGD resistance in 200 bar CO2 is going to be a tough call

Steve Jones
Materials & Corrosion Engineer

RE: High Pressure CO2 Pipeline Valves

I agree with SJones on difficult sourcing for the mentioned working conditions, I have tried cross referencing (Seals & Sealing handbook 2nd edition...yes I am that old) Temp, Pressure & Fluid without finding one single seal material that is good with all of them at the same time.
Maybe you can find required (or close as...) in this link http://www.elderrubber.com/material.htm Ciao,

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