Hydrochloric Acid-30% and Category M Fluid service

[Piping Engineer]

Hello everyone,
I have a question regarding to Hydrochloric Acid piping specification,
Pressure: 1200 up to 1720 kPa
Temperature: -29 up to 50 Deg C (it seems it wouldn’t have that much fluctuation it would be around 20Deg C)
Concentration of Acid: 30%
Current Pipe spec for this service is HDPE DR9
The client considered HCL as Category M fluid service and as per our Design Code ASME B31.3,
It seems we can’t use thermoplastic materials as per Paragraph 16.4 “Overview of Nonmetallic Rules” in Complete Guide to ASME B31.3, 3rd edition by Charles Becht IV
Thermoplastic and reinforced plastic mortar are permitted only as lining and for thermoplastics, gaskets (para MA323.4.2), the same paragraph in ASME B31.3.
So, my understanding is not to use PVC, HDPE, CPVC
In general thermoplastic piping are prohibited only as lining.
Am I correct? What is your suggestion?
I really appreciate your feedback and help.

 

[EdStainless]

FRP
Some sites have good performance out of lined steel pipe, at other sites it is a nightmare.
There are Ni alloys that are used, but which ones will work for you depends on trace impurities (low ppm ranges) and oxidation levels.
These prove to be very site/process specific.

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P.E. Metallurgy, consulting work welcomed

 

[Piping Engineer]

Thanks FRP for your quick response,

I have three questions:

1- Did I understand the code correctly , that we can't use Thermoplastic piping for Category M Fluid Service?

2- If I use lined steel pipe (PVC lined, Rubber lined) nature of these lined steel piping is to be connected by flange rather than welding, in this case more flange means more possibility of leakage which is exactly opposite of what we need in Category M Fluid Service.

3- which Nickel alloy do you recommend for 30% HCL?

Thanks,

 

[TugboatEng]

I believe Ed was suggesting Fiber Reinforced Plastic pipe which does not imply a thermoplastic.

https://www.google.com/url?sa=t&sou...wQFnoECB8QAQ&usg=AOvVaw1Mz7yvsYH3aYUNDRvyUqvs

 

[Piping Engineer]

Thanks TugboatEng for your response,

As far as I understand, FRP is a Reinforced Plastic , which is still prohibited (only as lining) for Category M Fluid service as per the following paragraph of ASME B31.3:

Thermoplastic and reinforced plastic mortar are permitted only as lining and for thermoplastics, gaskets (para MA323.4.2)

 

[EdStainless]

I don't believe that you are reading that correctly.
The FRP formulations that are used for this service are a glass fiber reinforced thermoset resin formulation.
This isn't just a reinforced thermoplastic.
The exposed interior is either the same resin (pure) or another resin selected for corrosion resistance.
This is the most common solution in HCl applications.

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P.E. Metallurgy, consulting work welcomed

 

[MJCronin]

This is a very good and useful discussion ..... but

What has not yet been mentioned yet is the accident implications of fire with non-metallic piping systems.

Additionally, there is a certain degree of physical abuse at any process plant ... Plastic pipes sometimes do not survive

Neither FRP nor any other of the plastic materials suggested would survive any kind of plant fire, but a lined carbon steel pipe would

An excerpt from this link:

https://www.oxy.com/globalassets/do...s/chlor-alkali/hydrochloric_acid_handbook.pdf

Lined steel is often used in piping system for
hydrochloric acid because it is the most structurally rigid
and is less likely to be adversely affected by physical
abuse. Lined steel systems also do not require gaskets
at flanged connections. The liner itself acts as the gasket
mating material. Common lining materials are
polypropylene (PP), polyvinylidene fluoride (PVDF) and
polytetrafluoroethylene (PTFE). Pipes are typically
carbon steel manufactured to ASTM F-1545
specifications.

Additionally, lined CS piping requires fewer pipe supports than plastic or FRP systems ....



MJCronin
Sr. Process Engineer

 

[EdStainless]

Good question, which would last longer in a fire, lined CS or FRP.
I don't know.
In lined steel once the liner fails you only have hours before the steel leaks.
These systems usually have monitoring to detect acid behind the liner.
Of course I am talking about loose lined, because the first rule with bonded liner is that it never stays bonded.
I have seen systems that are mostly FRP but in high risk areas (near lots of traffic for example) they use Ni alloy pipe.
This is really operator preference and it can be site specific.

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P.E. Metallurgy, consulting work welcomed

 

[Piping Engineer]

Thanks for your answers,
Another question raised here , if we want to go forward with lined steel, because all the line steels are usually Flanged connections (not welded) so we have more flanges in our piping network and more flanges could cause more leakage which is 100% prohibited in Category M fluid service.
How we can avoid this to have minimum risk of leakage?

 

[TugboatEng]

If you're concerned about fire resistance, how does the pipe perform at the boiling temperature of the liquid? Halogenated plastics can perform quite well in fire conditions.

What is this about flanges causing leakage? That risk can be minimized. The obvious is gasket selection and fastener tension procedure. Less obvious is face material selection to prevent crevice corrosion.

If you run lined pipe consider cladding the flange faces and a shirt way in to the bore of the pipe in nickel prior to application of the liner.

 

[EdStainless]

In most loose lined pipe the liner wraps the faces of the flanges.
Yes it is a lot of flanges, and yes they must be tightened very carefully.
There are a few different systems out there for handling these issues.
You need to do research into them.

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P.E. Metallurgy, consulting work welcomed

 

[Piping Engineer]

Thanks Edstainless,
The reason of my question is exactly what you have raised.
If other members can help me to resolve this issue I really appreciate it.
I want to see if anyone else had this issue in the past or heard about it and can help to resolve it.