FKM Oring for CNG
FKM Oring for CNG
(OP)
I am using a VM835-75 oring for a high pressure CNG application. Problem is at -40 C temperature oring is unable to hold pressure and leaking. Failure happens only if i soak the part at -40 C under 1000 Psi pressure than after one hour increase pressure from 1000 to 2000 psi. If i soak it at 2000 psi to begin with it doesnt fail. whats going on? VM835-75 is supposed to be good for -40 C.
Thanks
Raheel
Product Engineer
Thanks
Raheel
Product Engineer





RE: FKM Oring for CNG
At 2000 psi the o-ring is forced into the gland surface irregulaities, whereas at 1000 psi it is not and the seal material is too stiff at -40C to further conform and will not pass the subsequent 2000 psi test.
Ted
RE: FKM Oring for CNG
Regards
Ron
RE: FKM Oring for CNG
RE: FKM Oring for CNG
SAEJ200 M4HK710A1-11B38EO78F17
That is about as good as you are going to get for low temperature sealing from FKM. It is rated for -40C but I still doubt it would take a change from 1000 to 2000 PSI.
I think you should really consider using FMVQ, it is easy to get good sealing well below -40. I would look at specifying something like:
SAEJ200 M2FK606A19EF31E036F19Z1Z2
Z1 = 70±5 Shore A Durometer Hardness
Z2 = 8 MPa min. Tensile Strength
The F19 gets you -55C.