Summary for ptfe valve seats Discussion
PTFE valve seats are the focus of this thread, where Joshua Thinakaran asks whether socket-welded ball valves in compressor-module piping should have their PTFE seats removed before chemical cleaning and pickling. He lists aggressive cleaning chemicals for stainless steel and carbon steel lines, including HF/HNO3 for SS, HCl with ammonium bifluoride and inhibitor for CS, followed by citric acid rinsing and sodium nitrate passivation. The reply from A. says that, assuming the valves are PVC socket-welded ball valves and temperatures are medium-low (under 140 °F), there is nothing to worry about regarding the Teflon/PTFE seats. However, A. cautions that the seals may be a concern and recommends Viton over EPDM for this service, while also advising checking with the valve manufacturer. A. adds a personal preference for Plast-O-Matic valves for long-term service.
Q. We are fabricating a compressor module for ONGC Project in India. As per specification we need to carry out chemical cleaning of piping lines with following chemicals
SS Lines
Chemical Used for pickling is 0.5%HF(concentric) by volume on 100% purity basis & 13% HNO3 by volume on 100% purity basis. Time of pickling will be 1 hr. max
CS Lines
Chemical used for pickling is 33% HCl (5-8% by weight). Ammonium Bi Fluoride 0.5% by weight. Inhibitor Rodine 0.2% by volume.
Rinsing with citric acid
⇦ on
or
Amazon [affil link] and passivation with Sodium nitrate.
My question is the lines contain Socket welded Ball valves. The valves are having PTFE seats. Do we need to remove these seats during chemical cleaning? Are they vulnerable to attack by above mentioned chemicals?
Please advise.
Best Regards,
Joshua Thinakaran
Oil & Gas Projects – Mumbai, Maharashtra, India
2003
A. Hi Joshua !
Well, you mentioned all the lovely acids but didn’t say a word about the material for the lines and valves … so I’m assuming you are using PVC SW ball valves and that the temperatures are medium low, ie. under 140 °F You have NOTHING at all to worry about regarding the teflon seats. Nothing! But you might be concerned about the seals! Those valves normally come with either EPDM or Viton seals and for your case, I’d only opt for viton.
Check with the manufacturer … I’m biased myself and for super long term service I had used Plast-0-matic valves.
Freeman Newton [deceased] (It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
A. The request for Removal of Teflon is being answered. There is no need to remove the Teflon gaskets as there is no problems with them on line during chemical cleaning. We are in the field of chemical cleaning for over three decades.
Regards,
Suresh Venkataraman
– Gujarat, India