Required Examination of PTFE Lined Steel Pipe with Tell-tale Holes 1

[Inspector67]

ASME B31.3 like other codes sometimes cannot be straight forward. We are fabricating (welding) steel pipe with a PTFE liner. The steel pipe will have a tell-take hole to indicate if there is a breach in the PTFE liner. I believe this is still consider Normal Fluid service requiring 5% Radiography Examination of the steel pipe. What have you done at your job?

 

[LittleInch]

Depends on the pressure. Is the liner able to take full pressure without the outer pipe?

If not then the pressure containment strength comes from the steel pipe and therefore it needs testing as though it is the primary containment.

The weep hole is irrelevant.

Put a tapping on it and then it becomes like any other pipe with a tapping on it.

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

 

[dik]

What is a tell-take hole? Is this some form of 'inspection port'?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Inspector67]

We are performing a 450# hydrotest with the PTFE installed in the steel pipe. I doubt the PTFE liner could handle the pressure alone. I agree the tell-tale is irrelevant. I did find in B31.3 Chapter VII A300 (d) does state metallic piping that provides the pressure containment shall conform to Chapters I through VI. It's doesn't very clearly state if there is a tell-tale hole.

 

[LittleInch]

dik,

Lined pipe often comes with some sort of weep hole / gas release or liquid leak test connection - usually 1/2" or similar.

It prevents collapse of the liner if gas gets behind the liner and you depressurise plus tells you if the liner has sprung a leak.

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

 

[dik]

Thanks, LI...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[HTURKAK]

tell-take[/b] hole]

Probably typo.. Shall be TELLTALE..

Telltale hole , telltale pipe etc ( used for inspection , to deteck if leaks , to check corroded thickness ..etc)









Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[r6155]

See B31.3
A328.2 Bonding Qualifications
A328.2.1 Qualification Requirements

Regards

 

[EngrPaper]

One thing to be aware of with lined pipe, just in case this is relevant to your hydrotesting. All manufacturers 150# piping is normally rated to the full flange rating for 150#. But for 300# piping, no manufacturer actually goes to full flange rating. They all have various max pressure cutoffs far below 300# flange ratings due to liner limits on pressure and temp.

 

[shvet]

@Inspector67
What is design code? Is pipe lined or double-wall actually - there is a big difference?
Some instructions for test may be found in ASTM F423 or F1545. Weephole requirements see para. 5.3 in those.

 

[LittleInch]

Engrpaper,

Really? I can't recall seeing this before, can you link to some manufacturers please.

Usually the liner isn't the pressure containing part so it doesn't matter that much.

Temperature I can see, but pressure?

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

 

[EngrPaper]

LittleInch, when I surveyed this a while back Resistoflex had the highest class 300 flanged pressure rating. I've got their design manual here on my desk and I think this is the PDF version:

https://cranecpe.com/wp-content/uploads/Resistoflex-DM-2020.pdf

They had the highest pressure rating of all the manufacturers that I found. Its been a hot minute since I looked at it, but here are the results from my research. I was looking at a 200F acid application.

Pressure Survey of 300# Lined Pipe (Pressures at 200F)
• Resistoflex – 475 psig
• Mersen – 300# offering not found
• Aegis – 390 psig (HPLP series)
• Baum – 390 psig
• DuFlon – 300# offering named on website without information.

It didn't make a ton of sense to me either on why it was pressure limited. I chatted with Resistoflex on it, and I recall it being something about the transition of the pipe liner into the formed raised face part.

 

[LittleInch]

Aaaah, ok,

Now I know what you're looking at.

Yes, how lined piped are either jointed or flanged is a key aspect to how they work.

For me "lined" pipe is made initially as a steel pipe welded together and then you line it by inserting a tube inside it and pressurising it back to the stell surface, or internally lining it past jointing. but then I'm a pipeline engineer not a plant piping man....

Where you have the lining coming over the flange surface so that is in compression then you're in a different world of pain as indeed creep and visco-elastic behaviour starts and the whole thing starts to leak after while under the higher contact forces of a class 300 system.

Often you end up with special end connectors made from super duplex or some other high resistance alloy which then seals the inner liner or you protect the contact surface from the lining material / coating using a flange that isn't impacted but pipe material that would otherwise fail.



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

 

[EngrPaper]

That makes sense for using a more exotic alloy to get over the connections. Normally with lined pipe for plant use it's all a flanged system that is predominantly shop made. Fabricating it is pretty close to as you described for PTFE liners.

For PTFE, they essentially press fit the liner in a 20' length of pipe with a lap joint (or sometimes slip on) on both ends and with a hot mandrel they flare the liner over the lap.

For other plastics, like ETFE and I think PVDF, they melt billets of it in a rotating oven for even coverage and then machine the flange faces to size.