Graphoil stem seal fail

[Erkamal]

HI friends,
i am using PTFE lip stem seal for 5000 psi.

But i have made new globe valve for high temperature at pressure 10000 PSI but it is going to fail and leakage. when i am applying more force on seal. more friction has been generated between seal surface and stem surface. and it is going to shear.

Any one have idea about selection of seal like gland design .seal surface , seal cross section etc.


Kamlesh

 

[Danlap]

Hi Kamlesh,

I have success story with special graphite. test medium Helium at 200 bar and 400degC
configuration as follow

Eriks Special Packing Set from bottom to top: Hard carbon bottom ring; 2 end rings 6559 and 3 intermediate 6501-40 rings with Klüber Wolfrakote impregnation.

Success parameter: with only 1 time re-tightening at high temperature, its still manage desirable Fugitive Emission Class B.
Ask your packing supplier and advise over installation. Some packing configuration may requires pre-compressed one by one packing ring during installation. Instead of one time gland packing tightening after all the rings placed inside.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[jbeckhou]

You can use U-packing or sometimes called J-packing. Item 8 on attached drawing.

Petrotrim Services, LLC

http://www.petrotrim.com

 

[Erkamal]

Thank you friends.

I used Graphoil stem seal in one of Globe valve with 10000 PSI.

But at the stage of proto type of Globe valve. valve stem has been jammed. it was because of much force on Graphoil stem seal. and if i m going to loose force, leakage has been started.

SO i do not know what is going to happen. is it possible to select wrong seal cross section and height?

 

[Danlap]

Hi Erkamal,

You're not clear on the problem, design and function of the valve. By that respect, your hypothesis of wrong packing selection might be your least problem.
The first step in solving a problem is to recognize that it does exist. And in my opinion leaking gland is not your root cause problem, but with all due respect the information you've had at the moment and lacking of effort to find more information (or even try to elaborate the complete story). Which I find quite concerning if this come from manufacturer.

What is this valve for? On/off or control? both are different since gland compression factor, hysteresis as well as friction are different.
What packing are you using. Standard graphoil indeed not (directly) suitable for pressure above let say 25 MPa. Further does your packing manufacturer tell you about the seating stress of the packing?
What standard used for your valve?
Do you know anything about compression factor or standards for packing tolerance?

If you wish to do empirical analysis as your way forward, suggest to follow similar path as follow:
PS: I google it within 1 min

http://teadit.com/la/images/publicacoes/ASME_2008-Valve_Packings_Seating_Stress.pdf

https://www.jameswalker.biz/en/pdf_docs/6-compression-packing-guide-issue-9

Some reference that is handy already stipulated in the standards
ISo 10434
ISO

and EN 13555

Information required from your side is type of packing (in detail), Seating stress, gland bolts used, friction coefficient used can be a starting point.
And yes, bluntly assessment a wrong cross section and tolerance may lead to valve jamming, over squeezed, or leaking. Or all three.
Please don't reinvent the wheel, since if this gland packing faulty in the future, the Plant that you've supplied the valve with, should order "industrial type" packing that is available.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376