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Will PTFE Valve Seats be damaged by pickling of valves?




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 eBay or Amazon] 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 portrait
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




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