PTFE lined pipe calculations
PTFE lined pipe calculations
(OP)
Greetings,
I have to prepare documentation for notifed unit and I encountered some problems. I have to calculate minimum wall thickness and flange connection acc. to ASME for PTFE lined pipe (A105). It's already prefabricated with flanges and manufacturer guarantee it like CL150 pressure resistance.
Should I calculate it like normal steel pipe made of A105 carbon steel or is it another procedure for that kind of pipes?
Thanks in advance
Grzegorz
I have to prepare documentation for notifed unit and I encountered some problems. I have to calculate minimum wall thickness and flange connection acc. to ASME for PTFE lined pipe (A105). It's already prefabricated with flanges and manufacturer guarantee it like CL150 pressure resistance.
Should I calculate it like normal steel pipe made of A105 carbon steel or is it another procedure for that kind of pipes?
Thanks in advance
Grzegorz





RE: PTFE lined pipe calculations
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RE: PTFE lined pipe calculations
RE: PTFE lined pipe calculations
RE: PTFE lined pipe calculations
According to my somewhat limited experience in their use for pressure piping, coatings, liners and claddings are always ignored for pressure design, unless of course should the application of the cladding somehow weaken the base pipe.
"He's declaring war on the planet itself."- Vicente Fox
RE: PTFE lined pipe calculations
Regarding the vent holes, I am assuming you mean the small holes in the steel pipe wall for permeation evacuation. These are generally ~1/8" and are ignored, in my experience (I don't generally do ASME piping calcs first-hand but I've never heard it come up as a factor). However, depending on the process you may end up with some corrosion over time at these exit points. There will be some limit to how large this vent hole in the steel can become before your PTFE is at risk of blowout. Obviously, this is going to be depending on pressure, temperature, and your particular liner attributes.
You could also reach out to resistoflex or other lined pipe manufacturer, they will generally have some good guidance on how they calculate things to fit ASME code. One example is on PTFE lined tees; the way they line them basically means a full-pen weld of the steel is not possible, so they did some modeling to prove it is still strong enough and safe and have some sort of variance through ASME to still be able to say it qualifies as B31.3 piping.
RE: PTFE lined pipe calculations
Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.
RE: PTFE lined pipe calculations
Also note, some smaller diameter piping as well as the "loose" lined sections i.e. "Thermalok" are fabricated with threaded flanges and the liner flared over; on shorter runs they won't require vent couplings since the vapors can vent through the threaded flange connection.