Coated CS bolting for cryogenic service
Coated CS bolting for cryogenic service
(OP)
I have spec which reads that for a cryogenic application (design T approx. -325 F), A320 L7 bolts + A194 gr 7 nuts, both PTFE coated, will be used.
From B31.3 (applicable design code), I believe L7 may not be used at that temperature. Environment is inside a building, highly corrosive fluids.
From an application point of view, would anyone suspect a problem?
I have no background in cryo's, but something tells me L7 at -325 F may become too brittle. However I dont know what the PTFE will 'do to it'.
From B31.3 (applicable design code), I believe L7 may not be used at that temperature. Environment is inside a building, highly corrosive fluids.
From an application point of view, would anyone suspect a problem?
I have no background in cryo's, but something tells me L7 at -325 F may become too brittle. However I dont know what the PTFE will 'do to it'.





RE: Coated CS bolting for cryogenic service
ASTM A320 requires impact testing of L7 at -150 F, with a minimum energy of 20 ft lbs. Cryogenic applications at -325 almost always use an austenitic stainless steel such as grade B8 from ASTM A320.
RE: Coated CS bolting for cryogenic service
Put short, it means L7 wont do the job, and they'll probaly become too brittle and break at some notable event.
RE: Coated CS bolting for cryogenic service
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RE: Coated CS bolting for cryogenic service
RE: Coated CS bolting for cryogenic service
RE: Coated CS bolting for cryogenic service
RE: Coated CS bolting for cryogenic service
For prevention on galling, corrosion, decrease bolt stress, etc.?
RE: Coated CS bolting for cryogenic service
Just be aware that many of the coatings also become brittle at cryo temps.
I have seen bolts made of 625 used for service that required the combination of high strength, corrosion resistance, and wide temp range (625 will handle -400F to 1400F).
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