PTFE O-rings

[smart2006]

I read the following article on Wikipedia as follows:

"Because of its chemical inertness, PTFE cannot be cross-linked like an elastomer. Therefore it has no "memory," and is subject to creep (also known as "cold flow" and "compression set"). This can be both good and bad. A little bit of creep allows PTFE seals to conform to mating surfaces better than most other plastic seals. Too much creep, however, and the seal is compromised. Compounding fillers control unwanted creep and improve wear, friction, and other properties. Sometimes metal springs apply continuous force to PTFE seals to give good contact, while permitting some creep."

However we are using PTFE o-rings at our plant site.

 

[flexibox]

Without knowing where you use PTFE Orings, there is nothing wrong in using PTFE in your plant. When fitting PTFE Orings to mechanical seals you need to pre-heat the Oring in hot water or heat them up with LP Steam. Generally speaking if the Oring is static (Solid PTFE) then you will most likely need to use a press to fit the Oring into place. If the Oring is fitted by hand then there is a good chance that the housing diameter is not correct. Having said that if the fit is too tight then you may experience face distortion. This is why people machine the diameter out to prevent face distorsion. If the dynamic Oring is also solid then you MUST preform the Oring on a mandrel (Dummy Shaft) whilst it is hot so that it takes shape of the shaft. The key is to ensure that the seal is able to slide by means of the spring force. If the seal sticks during this process then keep pre-forming the Oring until such time that the spring force can push the face fitted with the Oring freely. If you are experiencing pre-mature seal failures using PTFE Orings check your fitting procedures.

Good Luck