WKTaylor
Well-known member
- Sep 24, 2001
- 4,094
Guys... I have a dilemma and need Your advice.
NOTE. All my aircraft’s ‘systems’ have hydrocarbon or synthetic hydrocarbon fluids [primarily fuel, engine-oil, hydraulic-oil]. Lubricating grease is omitted from this question.
Old technicians [and older tech data] taught me to install rubber seals [O-rings, gaskets, etc] after ‘soaking’ [conditioning] the seals in ‘the fluid’ that the system uses… for a few minutes [~15-minutes or more]… or a similar type oil or fluid [clearly compatible with 'the fluid', such as the 'universal fluid' MIL-DTL-5606 hydraulic oil]. After ‘soaking’ the seals… started well-before final component assy… the part was then ready for installation. The rational I have for soaking rubber parts in fluid is that the ‘fluid’ needs time to absorb slightly into the rubber surface pores hence ‘better-wetting’ the part surface and preparing the rubber for [that] fluid service.
Recently I have encountered tech documents where petrolatum is the lubricant of choice. ‘Butter’ lube the part lightly with petrolatum and then immediately install it into the Assy. NOTE: some documents do warn against this practice [using petrolatum] for non-hydrocarbon fluids, such as Skydrol.
Petrolatum is specifically topical and is a grease-like substance that may/may not be 100% hydrocarbon fluid compatible… but appears to be ‘assumed-to-be compatible’ by these documents.
Problem/concern.
A LOT of our elastomer seals [O-rings] are MF Nitrile rubber per AMS-P-5315.
Per ‘AIR786 Elastomer Compatibility Considerations Relative to Elastomeric Sealant Selection’, the -5315 rubber is highly compatible [Satisfactory] for use with hydrocarbon fuels and oils [S rating]; but it is rated ‘Fair’ [F rating] for petrolatum… which sorta confirms/reinforces my discomfort with the petrolatum lube practice… especially when assys may be shelved/left-open indefinitely before use.
What is/are your experiences with seal lubrication for installation into a system, RE this question [and/or etc]?
NOTE. These acft have been transitioned from JP-4 to JP-8 and now are running mostly Jet-A+additives. There have been similar changes revisions] to system hydraulic oils and engine oils.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
NOTE. All my aircraft’s ‘systems’ have hydrocarbon or synthetic hydrocarbon fluids [primarily fuel, engine-oil, hydraulic-oil]. Lubricating grease is omitted from this question.
Old technicians [and older tech data] taught me to install rubber seals [O-rings, gaskets, etc] after ‘soaking’ [conditioning] the seals in ‘the fluid’ that the system uses… for a few minutes [~15-minutes or more]… or a similar type oil or fluid [clearly compatible with 'the fluid', such as the 'universal fluid' MIL-DTL-5606 hydraulic oil]. After ‘soaking’ the seals… started well-before final component assy… the part was then ready for installation. The rational I have for soaking rubber parts in fluid is that the ‘fluid’ needs time to absorb slightly into the rubber surface pores hence ‘better-wetting’ the part surface and preparing the rubber for [that] fluid service.
Recently I have encountered tech documents where petrolatum is the lubricant of choice. ‘Butter’ lube the part lightly with petrolatum and then immediately install it into the Assy. NOTE: some documents do warn against this practice [using petrolatum] for non-hydrocarbon fluids, such as Skydrol.
Petrolatum is specifically topical and is a grease-like substance that may/may not be 100% hydrocarbon fluid compatible… but appears to be ‘assumed-to-be compatible’ by these documents.
Problem/concern.
A LOT of our elastomer seals [O-rings] are MF Nitrile rubber per AMS-P-5315.
Per ‘AIR786 Elastomer Compatibility Considerations Relative to Elastomeric Sealant Selection’, the -5315 rubber is highly compatible [Satisfactory] for use with hydrocarbon fuels and oils [S rating]; but it is rated ‘Fair’ [F rating] for petrolatum… which sorta confirms/reinforces my discomfort with the petrolatum lube practice… especially when assys may be shelved/left-open indefinitely before use.
What is/are your experiences with seal lubrication for installation into a system, RE this question [and/or etc]?
NOTE. These acft have been transitioned from JP-4 to JP-8 and now are running mostly Jet-A+additives. There have been similar changes revisions] to system hydraulic oils and engine oils.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]