Piping as "Pressure Vessel" Code ASME Code

[rrebeiz40]

Hello, this is my first post, thanks for your time.

This is a question regarding code.
I have a 30gal pressure vessel need for the plant's high purity argon line. The receiver tank must be clean of dust, oil, anything that can contaminate the line, but it's impossible for any vendors I know of to clean tanks this small. So we're exploring constructing our own tank out of about 6 feet of 12inch SCH40 pipe sealed with bolted plates to welded flanges that way we can readily clean it. I have searched for code relevant to this, the only thing I could find was B31.3 para 304.7.2, and that's not even that relevant. I did the cylindrical and weld stress calcs (max pressure in our main is 200psi), safety/design factor of 12. So if 304.7.2 is relevant, we're good to go. All the components of this make shift "pressure vessel" are off the shelf components meant for this service, all weld and splicing techniques will be per best/standard practice. Am I missing anything that may place this under ASME pressure vessel codes and require a rating and other qualification? Also, does it make a difference if this large dia pipe was in-line with the rest of the line, rather than being T'd off from the line? For this application, the tank could be in-line or T'd off and it would not make a difference. Having it in-line seems to me like it would make it less likely to be considered a pressure vessel.
If i need to clarify anything, ask. Here's some pictures to help. T'd off would look like the left, in-line would look like the right. most likely 1in pipe and 12in pipe/tank. Thank you for input.

Thank you

 

[bimr]

This has been previously answered:

http://www.eng-tips.com/viewthread.cfm?qid=154373

 

[TD2K]

Take your 6' of 12" pipe, weld on class 150 WN flanges to it and bolt on 12" blind flanges. Assuming your temperature is below 100F which seems reasonable for an argon line, you are good to 285 psig or more depending on the class of material. Class 150 flanges are good to 200 psig up to about 400F so again, you should be good. Install suitable connections in your piping as needed so you can remove the blind flanges as needed for subsequent cleaning or inspection.

Read U-1(c)(2) and then U-1(c)(2)(-e)

(2) Based on the Committee’s consideration, the following
classes of vessels are not included in the scope of
this Division; however, any pressure vessel which meets
all the applicable requirements of this Division may be
stamped with the Certi fication Mark with the U
Designator:

(-e) piping components, such as pipe, flanges, bolting,
gaskets, valves, expansion joints, fittings, and the pressure
containing parts of other components, such as
strainers and devices which serve such purposes as mixing,
separating, snubbing, distributing, and metering or
controlling flow, provided that pressure containing parts
of such components are generally recognized as piping
components or accessories;

 

[zdas04]

Take a look at thread794-58577. For something that came under B31.8 this would be a slam dunk. It would be a pipeline accessory since it satisfies all of:
[ol 1]
[li]Can be described by a piping sketch or iso drawing and referenced piping specs.[/li]
[li]Is not intended for storing or processing fluids. The exception is items such as mixers, tees, headers, metering devices, or other items that are typically recognized as piping components.[/li]
[li]Its primary function is to transport liquids and gases from one location to another within a piping system of which it is an integral part.[/li]
[li]It is not intended to act as an air receiver.[/li]
[li]The item will not be subjected to more frequent test and inspection intervals than the remainder of the attached system[/li]
[/ol]

Under ASME B31.8 (Section 831.35(d), Special Components Fabricated by Welding) formalizes this some by saying [emphasis added] “Prefabricated units, other than regularly manufactured butt welding fittings, that employ plate and longitudinal seams as contrasted with pipe that has been produced and tested under one of the specifications listed in this Code, shall be designed, constructed and tested under the requirements of the BPV Code.” B31.8 clearly draws the line at longitudinal welds as opposed to pipe (including ERW and other piping fabricated by the manufacturer from plate to an included specification) and butt weld fittings.

I looked in B31.3 and couldn't find a similar paragraph.

For this analysis it doesn't matter if it is inline or located in the branch of a tee.

Just wondering, why you are using flat plate instead of weld caps? If it is the cleaning thing, then why not one weld cap and an ASME B16.5 flange and blind on the other end.?

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

RRebeiz40,

If you look the responses and the other posts which have chewed this over the key factor is who is authorising this externally and what is their call on it. It could fall into ASME PV code due to pressure and size.

In zdas04s response, I would take issue with item 2 - it is pretty clear from your post that this thing is intended to be used to store argon (you call it a tank and a receiver).

In this instance I think it falls on the Pressure vessel side of the line between piping and PV.

Therefore the issue is then whether under the PV code can you use standard piping items. I don't understand why your "bolted plates to welded flanges" is being designed separately and not using a bind flange to B16.5? You can place a hole in the centre of a blind flange - see multiple discussions on this point on this site.

You could build this out of piping components and claim that it is simply part of the system, in which case having a distinct flow in, flow out path would help.

This probably muddies the water a bit, but the key factor is the regulatory view.

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

 

[BigInch]

#2 I'd be willing to discuss #2. My problem is #3. In no way can it be part of a B31.8 pipeline, it has argon inside it and is not attached to a pipeline intended for the transportation of natural or other hazardous gas via pipeline. Nobody even said "pipeline". It is apparently just some kind of a "plant's" piping system.

 

[zdas04]

#2 is from the BPVC, it says (in the Section VIII preamble) that wide places in the line are not "storage" or "processing" even though you frequently get a mechanical or thermodynamic change with the drop in velocity.

I also had a problem with #3. When I put a line drip in a B31.8 pipeline, #3 is no problem, but inside a B31.3 facility it is a stretch. If I was doing it I would make very certain that I had my "engineering judgement" properly documented and on file.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

I don't have a copy of ASME VIII, bt the key to me is in the word "intention". It's pretty clear to me that the intention is for storage, not just a consequence.

I actually don't think there is any real mechanical issue here, just one of jurisdiction and CYA. I would design it to 31.3 to make it a bit more robust, but otherwise this sort of thing is done all the time.

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

 

[BigInch]

The key word is argon. Just like an auxiliary compressed air system (in a compressor station), an argon system wouldn't be part of a pipeline, even if it was in a compressor station. Drip is certainly on a "pipeline" and has natural or other hazardous gas. Wear your legal hat under your engineering hat. IMO, B31.3

 

[moltenmetal]

A 12" section of pipe connected between two pressure vessels would be B31.3 pipe. A 12" section of pipe connected between two large vessels by 2" pipe would also still be pipe. But the same piece of 12" pipe, without the two vessels, with identical design, is now its own pressure vessel and requires ASME VIII fabrication and inspection and a U stamp.

As to finding U stamp vendors who are capable of doing the required cleaning- I hear you, it's tough to find ASME vendors who will take a mere 12" "pressure vessel" seriously, even if it were something as important as a reactor rather than just a receiver like this. Whoever would be cleaning your "pipe" could also clean this vessel after it has been built, and you're planning to design it so that it can be cleaned, so that's not really an issue in my opinion.

 

[rrebeiz40]

Thank you everyone for the very informative replies.

Couple more details on the project: We're a Titanium foundary. Our analysis lab needs high pressure all the time, but low flow rate. The rest of the equipment in the plant doesn't need very high pressure. When our furnaces backfill with argon the whole plant sees the pressure drop, which hurts the lab. Pressure recovers quickly. I determined a 30gal buffer, isolated from the plant by a check valve when the plant's pressure drops, is all that's necessary.

bimr, I read the article and I'm convinced the conservative approach is to contact a vendor that is certified to U stamp. That is if we choose to go with the 12 tank. I requested an estimate yesterday..

TD2K, I'm not sure I have access to those documents. I have II, VIII and B31.8.

zdas04, I'm a newb, I meant "ASME B16.5 flange and blind", not plate. Thanks for the correction and for the welded cap idea.

LittleInch, I'll definitely be contacting the authority on this topic to get their buy in and their opinion on where the line should be drawn. Yeah, I didn't mean "plate", my bad.. I think having it in series with the rest of the piping, therefore being an integral part of the system, would increase the chances we could do this without a stamp, so I'm exploring that, but I'll be OK if the authority requires a stamp anyways. I have a guy that can do this for me. Very good information, thank you.

BigInch, correct, this is just part of the plant's piping system.

Zdas04, do you think it would make the line more clear if instead I went with 11 ft of 8", or 20ft of 6"? 20ft is the entire length from the Main to the Lab.

LittleInch, if the volume is in series and therefore argon is constantly flowing through its inlet and outlet, is it storage? Running larger diameter where feasible can be a means for buffering a system. That is the intent. I will consider B31.3. in your opinion, would it need a U stamp?

moltenmetal, your analogy makes a lot of sense and sounds to me like the authorities will view it also. It's a good thing I am getting an estimate from a vendor that can U stamp. In your opinion, would it make a difference if it were not 20ft of 6" which is the entire length from the Main to the Lab.

 

[zdas04]

rrebeiz40,
Absolutely, if you had spec'd a 20 ft section of 8-inch (or whatever length/size gives you the line pack that you need) then no one would have questioned it at all. Put a pigging valve (make sure that your process can tolerate the receiver plate in the stream) on either end of it in case you ever need to clean the over-sized section. I don't think that your original idea would actually violate any codes, but doing it as a length of pipe would not raise any eyebrows at all.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[BigInch]

Having an inlet and outlet certainly does not classify it as "not-storage". It's not interesting to split hairs of word definitions when applying safety standards. This contains a large volume of compressed air or gas, whether flowing or not, and whether it is a built as a pressure vessel or pipe, it could be dangerous either way if not fabricated properly. The interest should be in fabricating this properly and keeping you legal. In that regard, what's your local building / boiler code say about pressure tanks and stamps.

Explain me again why you don't just buy a ready built. They seem to be all over the place, but as my Gramma always said, "Each to his own". (Actually don't explain. Just a figure of speech.) I think you'll spend more money building one yourself.

http://mantank.com/products/pressurevessels/index.htm

 

[LittleInch]

With the extra info you've supplied then yes I think it could easily be classified as just a piece of pipe which is bigger than strictly needed for transport, but with continuous in line flow where you're not removing the flange on a regular basis then it should avoid needing to be a pressure vessel.

Just design and test to B31.3 and that would satisfy me.

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

 

[BigInch]

Check the law here:

 

[Gator]

Your argon supplier (Air Liquide, Praxair, Air Products...) will be able to help. This is the sort of problem their customer installations departments routinely work on. Or at least they used to when I was working there.

Piping Design Central

 

[rrebeiz40]

Thank you again to everyone that has replied. I'm doing my do diligence to stay legal of course, but hopefully save money.

Biginch, Manchester tank does not clean or line tanks under 80gal. Typically not even under 200gal. I need 30gal, I could go up to 60 gal. The tank will service high purity argon which can't be contaminated by the oils/lubes used during fab, so a good epoxy interior coating, or similar, is required. Thanks for the boiler inspector link. Though for this I will contact our jurisdictional inspector through our insurance company. I believe he's the appropriate authority.

Gator, I talked to Airgas a while back, they weren't able to help with this application. They recomended renting argon cylinders that would maintain the required pressure when the plant dropped. We had already been looking at that idea and decided it was not as convenient for various reasons and would be more expensive after maybe 2-3 years. It's totally a legit solution otherwise.

Thanks again everyone for the input. I will contact the inspector and post here when I have an answer.

-FreeRange