"HF alkylation units screwed connections for instrument"

[0707]

In HF alkylation units all screwed connections for instruments require (Heavy-duty industrial-grade “extra-dense” Teflon “R” tape). Is it acceptable to use the same Teflon reference in the liquid form? What are others experience on inspection of screwed connections? As you see for safety reasons this is an important item which most of the time is forgot and leaks happen with consequences for operations, inspection and maintenance instrumentation.
From forum experience what are others procedures and experience for on line inspection of these screwed connections?
Thank you to the forum empathy.
Luis marques

 

[CoryPad]

The tape is applied to screw threads to fill the space between the external and internal threads and prevent fluids from leaking. How would liquid Teflon do this?

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ash9144]

I've always seen the tape used. Not just for HF units but even water pipe at home. The tape is cheap and readily available, the liquid (spray) not so much.

What leak issue are you having?

 

[dcasto]

most companies are getting away from tape and using a paste teflon. for high performance a nickle based compound might be better.

 

[EdStainless]

The teflon paste or the metal (Ni or Cu) bearing pastes are anti-seize compounds. The solvent will dry out of these leaving just a fine powder.
If you are relying on the tape to help seal then you have different issues to deal with.

= = = = = = = = = = = = = = = = = = = =
Still trying to help you stop corrosion.
formerly Trent Tube, now Plymouth Tube
eblessman@plymouth.com
or edstainless@earthlink.net

 

[0707]

PHILLIP HF alky unit licensor asks for the use of (Heavy-duty industrial-grade “extra-dense” Teflon “R” tape) on instrument screwed connections. I am investigating an incident leak through an instrument connection on an HF Alky process unit. On my investigations I concluded that maintenance people uses the same kind of Teflon in the liquid form it is a product from Chesterton called "900 Goldend paste". The leak on the screwed connection was due to corrosion on male and female screwed connection. My opinion is that Teflon tape gives more protection to the screw as it avoids the leak possibility and also gives some corrosion protection avoiding interstitial corrosion, rather than the same Teflon type in the liquid form.

I also would like from other refineries experiences in HF alky units what are the routine practices of on line inspection of screwed connections. We are thinking to start a programme of digital Rx inspection of screwed connections where practicable, according to a planning base on fluid criticality of the connection.

Please share

Regards

Luis Marques