PFA Liner detached from flange surface

[gatossi]

For one of our projects, we have a PFA Lined piece of equipment. On inspection, we found out that the liner is detached from the face of the flange (about 2-3 mm). The supplier claims that this is normal practice and the gap will close once the piece is bolted to the pipe. I am sure that will be the case, but I believe there will some stress put into the liner during the bolting process.
Is there any acceptance criteria on this? I have checked F1545 but there is nothing on clearance between liner and housing metal (or flange face, where we are seeing this)
My experience with lined pipe and fittings is that the liner is in contact with the flange face.

any help will be greatly appreciated!

 

[Compositepro]

This is common on the lined pipe that I've seen. The liner is not adhered to the pipe and it is non-structural. Usually there are weep holes in the steel pipe to vent any leakage or permeation though the liner. The gap is caused by spring back of the liner after it was formed to the flange. The flange prevents forming past 90 degrees so that the final shape is at 90 degrees.

 

[LittleInch]

Is the liner on the flange face?

That's normally not a good move as the lining can creep over time and result in flange leakage.

Linings around flanges are very problematic in terms of sealing as are linings .
How was this lined?

Any drawings, photos?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[gatossi]

Thanks CompositePro and LittleInch for your responses.

Yes, the liner extends to the flange face (standard practice in my experience)

The manufacturer also claims that the "detachment" is industry standard, in line with what CompositePro stated.

Thanks again guys, much appreciated!

 

[EngrPaper]

@LittleInch, I think you and I talked about this a while back. Lined pipe in chemical plants is normally a flanged system where the liner is formed over the face of the flange, hence gaskets are often not required. It is limited to 150# systems and a derated 300# system usually (for pressure, that is. temp is limited by liner material).

To the main question, PTFE liners do not adhere to the piping itself, they are just molded to it. I suspect it would be similar for PFA. The only ones I would question that for would be any piping that is roto-lined. In those cases, the liner is supposed to adhere to the metal substrate.