On Oct 23, 12:41*pm, "Jon Danniken"
wrote:
On 10/23/11 1:36 AM, DD_BobK wrote:

Teflon tape's major role is that of sealant.

No. *The main reason people use PTFE is to lubricate the threads so that the
fitting can be tightened tightly enough to provide a seal.

Additionally, the material itself, be it PTFE tape or the grease that the
PTFE is suspended in, provide an additional highly viscous barrier (sealant)
to any small leaks.

Jon

Jon-

"The main reason people use PTFE is to lubricate the threads so that
the fitting can be tightened tightly enough to provide a seal"

I can't know "the main reason people use PTFE" but......

If we are referring to NPT threads (the kind used in normal piping
applications & found by the 100000's in plumbing depts) .....lubricant
alone will not seal them, no matter how tightly they are torqued. NPT
threads are not designed to interfere.

The NPT thread forms have a "designed & mfr'd"crest to valley
clearance. This clearance forms a spiral leak path........sealant
required.

Only NPTF (dry seal tapered pipe threads) are meant to be uses w/o
sealant... complete metal to metal contact.

Check out the NPT thread form (Machinery's Handbook or other ref)
& you will understand the leak path. Complete metal to metal contact
does not happen.

cheers
Bob