edleit
Mechanical
- Dec 14, 2004
- 23
I've now come across several instances where the combination of PTFE tape and Krytox anti-seize compound have been specified in the pre-assembly preparation of male pipe threads.
A long, long time ago, I was taught as a young engineer that thread prep should be restricted to a single medium (pick one that's appropriate for the application). The rationale being that coating an already taped fitting/pipe end in this way would create a hydraulic efffect that might overstress the connection, or cause the joint to loosen over time.
Are there situations in which this approach would be considered appropriate for a fluid connection? I have seen postings on other fora regarding the combination used to secure bicycle hardware (mainly on high performance bikes with Ti components). This just seems odd to me, since each medium (i.e., tape or lube) is designed with a particular function in mind. For a stainless steel connection I can understand using Krytox to avoid galling, but usually on straight threads, not tapered. Likewise, a single layer wrap of PTFE tape provides a means to fill minute voids between the mating threads, whether the material is stainless, iron, or CPVC.
Does anyone else specify the combination on a regular basis, and if so, under what conditions is it deemed appropriate?
A long, long time ago, I was taught as a young engineer that thread prep should be restricted to a single medium (pick one that's appropriate for the application). The rationale being that coating an already taped fitting/pipe end in this way would create a hydraulic efffect that might overstress the connection, or cause the joint to loosen over time.
Are there situations in which this approach would be considered appropriate for a fluid connection? I have seen postings on other fora regarding the combination used to secure bicycle hardware (mainly on high performance bikes with Ti components). This just seems odd to me, since each medium (i.e., tape or lube) is designed with a particular function in mind. For a stainless steel connection I can understand using Krytox to avoid galling, but usually on straight threads, not tapered. Likewise, a single layer wrap of PTFE tape provides a means to fill minute voids between the mating threads, whether the material is stainless, iron, or CPVC.
Does anyone else specify the combination on a regular basis, and if so, under what conditions is it deemed appropriate?