PTFE tape or Copper washer 1

[RobertHasty]

Hi,

When using connections for pressurized sir (e.g. male stud adapter) do you prefer to use PTFE tape as a Seal or Cooper washer?

 

[Prometheus21]

It depends on multiple factors, but I'll give it a shot, but my experience is just from the industrial gas industry:

Short answer: For tapered thread - teflon tape. For parallell threads - copper gasket or washer depending on the connection design.

The sealing type heavily depends on the system parameters and customer requirements - pressures, temperatures, the fluid itself, acceptable leakage rates, +++, and in these days; material availability (in certain countries). My company had issues getting copper gaskets and washers for a long time from our suppliers.

Generally speaking:

1. Tapered threads needs teflon tape (e.g. BSPT, NPT) to seal. For high pressure industrial gases teflon tape is also used for NPTF threads - even though the sealing happens on the threads themselves, this is only partially true for high pressure systems - spiral leaks are quite common.
Gas cylinder threads (tapered) are also used in combination with teflon tape - 17E & 25E. W19,8 x 1/14 and other tapered threads are also used with teflon tape with no issues.

2. Parallell threads like BSPP threads have multiple sealing methods (as the pressure tight joint are not made on the threads). For these threads a copper gasket or washer is quite common. Using teflon tape is possible I suppose, but it is a very poor choice (again, in the industrial gas ind.).

* Bull nose and cone seal (metal to metal - no leakage. One of the more common sealing methods in the industrial gas sector).
** O-ring seal (requires more inital focus on proper material selection but is very popular due to ease of assembly)
*** Gasket sealing (It will require a specific amount of squeeze to properly seal - can be tricky. Some customers have a tendency to overtighten, cracking the copper gasket and creating a leak path).

There are some other sealing methods of course but I'll leave it at this.

 

[RobertHasty]

Hi Prometheus21,

Sorry for a delay in my reply.
Thank you for a very extensive elaboration.