Butterfly valve: PTFE vs. TFE

[562350]

I am selecting butterfly valves for Hydrochloric acid lines. There are two options for the liner/seat: PTFE and reinforced TFE. What is the major deference between these two teflons?

 

[MikeHalloran]

The reinforcement, whatever it is.

TetraFluoroEthylene is a gas. It polymerizes to become PolyTetraFluoroEtheylen, or PTFE.




Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[joeswoes]

You might want the specifier to clarify the term "reinforced". This can be construed as

1. Filled with an inorganic fiber such as fiberglass. This hardens the polymer and will create a very high torque valve if bubble tight shut-off is desired. The need for glass reinforcement is questionable for just HCl service.

2. Dyneon TFM or Dupont NXT PTFE. These are modified PTFE's, which some people could use the term "reinforced", only for the purpose of separating these materials from the standard PTFE's. They exhibit better stability at elevated temperatures, therefore acting like a reinforced material. Again, for straight HCl, unless it's really hot, I don't understand the need.

 

[RichDavis]

PTFE and TFE are seemingly used interchangably to identify the same materials. I agree completely with joeswoes about the issues of "reinforced". Reinforced can also mean other constituents in the structure. While PTFE is widely reistant to most chemicals, the other materials will not have the same level of resistance. Ask the vendor to give you the specifics on the reinforced version.

On the subject of TFM and NXT, both of these are considered to be "modified PTFE", not "reinforced". My experince with the modified PTFE has been very successful. Permeation resistnace is improved and mechanical properties are enhanced.

All PTFE linings are not created equal. Investigate the thickness of the liner. One good measure is the spark testing. The higher the Kva used to check for pin holes the better.