Is it a pipe or is it a vessel?

[roadwhore75]

We have an interesting situation at the refinery. Just as an example, we may have a 2" pipe expanded into a 24" or 36" or even, let's say, a 48" pipe. Appropriate ANSI flanges are used. The piping operates at about 1,500 psi and contains purified or recycled hydrogen.

Our mechanical engineers, and the engineering firm hired to run an additional pipeline from our H2 supplier thinks it's a pipe and so, therefore, no ASME code stamp is required.

Given the dimensions, with this section of expanded pipe serving as an expansion tank, I think the pipe should have an ASME Div. 1, since the pressure is less than 3,000 psig and H2, though a fire hazard is not lethal --- it is an asphyxiant.

Any thoughts? Is the expansion a pipe or is it a vessel? Obviously, taking this logic to the extreme, a vessel is merely a piece of pipe.

 

[nickelkid]

Assuming B31.3 and VIII-1 apply

I believe it can be considered a pipe.

Depending on material you using a pressure vessel built to section VIII-1 may permit higher allowable stress versus designing as a pipe it to B31.3. A potential cost savings.

 

[JLSeagull]

On a similar and different situation, I found nothing to prevent applying ASME B31.3 etc. in lieu of the ASME BPVC.

 

[moltenmetal]

The unwritten rule is that what matters is whether the item in question is the major volume of stored energy in the system, or not.

A 48" line connecting two huge vessels is B31.3 pipe.

A 48" expansion in a 2" line, connected to some control valves etc., walks and talks like an ASME VIII vessel- even if it's made entirely of pipe and pipe fittings. That remains true even if the 2" line is connected to a huge vessel at either end!

Ultimately it's the owner's call, since the code rules are NOT prescriptively clear on the issue of the 48" expansion in the 2" line. "Owner's call" sometimes means "owner's insurer's call". In some places, there's also a boiler/vessel/pressure piping authority which has jurisdiction (TSSA in Ontario, Canada for instance) who also must be satisfied.

 

[unclesyd]

You will have to check this out with your AI.

In the late 70's and early 80's I tried for years to make (8) 36" and 48" dia. vessels into pipe to save lots of money as they required periodic downtime and repair to all the associated flanges. I was denied permission to do this by an Insurance company ruling supposedly based on a ruling by ASME.

 

[metengr]

My suggestion is to carefully review the Scope statement of ASME Section VIII, Div 1. Paragraphs of interest include;

U-1 (c) 2 (d), and (e)

 

[jte]

Roadwhore-

Just because something is built of pipe and piping components does not mean it isn't a vessel. Depends on its application - is it primarily used for transport or is it primarily used to store or process?

Question: Is a pressure vessel intended for storage or processing of a fluid, built from piping components, exempt from the scope of Section VIII, Division 1 per U-1(c)(2)(e), if none of the other exemptions listed in U-1(c)(2) apply?
Reply: No.

These issues are often a gray area. One criteria I often use is to ask if the item in question has a level gage. Piping does not usually have level gages. You only need level gages if you are storing (even for a short time) liquid. There are long term inspection/maintenance/repair advantages to the operator if it can be labeled a piping component, so besides any initial cost issues, it may be more economical to call something a pipe if there is a good scope argument to do so.

jt

 

[AIOR]

Per Sect VIII-1 Scope (U-1(a)(2):
pressure vessels are containers for the containment of pressure...Also, per U-1(c)(2)(e) piping components are exempt.

 

[PVinspector]

If the primary purpose is to transport fluid under pressure, it is pipe.

If the primary purpose is to store fluid under pressure, it is a vessel.

A vessel can be very small, and a pipe can be very large, focus on the function.

Owner / user decides, jurisdiction must agree.

It is not that complicated.