ASME code exclusion requirements

[Arnieg]

Are all of the components mounted on the skid of a package centrifugal air compressor excluded from the ASME code? Typically centrifugal air compressor manufacturers install a tube and shell oil cooler on the air compressor skids of packaged compressor units. Most manufacturers do not relief valve protect either the oil side or the water side of these code stamped heat exchangers. All of the manufacturers that I have contacted content that so long as the compressor unit is properly installed, maintained and operated there should be no safety / code compliance issues. I.e., the compressor cooling water system pump dead head is less than maximum allowable compressor cooling water supply pressure or the compressor cooling water system is relief valve protected at a pressure that is less than allowable compressor cooling water supply pressure. Code requires that all code vessels be relief valve protected. I assume that this means that both the shell and tube side must be relief valve protected, (do both the shell and tube side have to be relief valve protected?). If this is true than unless the entire compressor skid is code excluded most package centrifugal air compressor systems are in violation of code requirements.

Do all code stamped vessels have to be relief valve protected? For example, does a code stamped heat exchanger that is less than 6" in diameter have to be relief valve protected?

Are these issues jurisdictional issues or are they cut and dry from cost to cost?

 

[jte]

Do all code stamped vessels have to be relief valve protected? For example, does a code stamped heat exchanger that is less than 6" in diameter have to be relief valve protected?

Yes. The stamp may be put on a vessel that is less than 6" in diameter U-1(c)(2)...however, any pressure vessel which meets all the applicable requirements of this Division may be stamped with the Code U Symbol. So unless the fabricator meets UG-125 thru UG-137, the U stamp should not go on the vessel. Sounds to me like they are taking a Code Case 2211 approach by arguing that the dead head can't reach the MAWP. That's fine, as long as the use of the CC is noted on the Manufacturer's Data Report.

Are these issues jurisdictional issues or are they cut and dry from cost to cost?

Jurisdictions vary. Some accept CC's without question, some require prior acceptance.

jt

 

[Arnieg]

I do not believe CC 2211 can be used when the fluid is water. It might be OK on the oil side.

 

[jte]

arnieg-

I've never dealt with CC 2211, but yes, paragraph a) seems to imply that, though I'm not quite sure 'bout the "unless" part of the sentence. I think the bottom line here is that the vessels (including both shell and tubeside of exchangers) need relief devices.

jt

 

[U076762]

Greetings,
I submitted an interpretation request to ASME on this exact issue and expect a response in the next issuance of Interpretations Vol 57.

I respectfully disagree with the assertion that simply because a vessel is Code stamped that it must comply with all Code requirements. It is my contention that vessels meeting the exemption criteria of U-1 (but the owner chooses to fabricate in order to gain the benefits that Code fabrication generates) do not need to follow any further Code requirements (e.g., UG-125 - UG-137) after meeting the fabrication requirements necessary for the stamp.

If they agree with jte's position then the effect is to discourage people from building quality Code vessels if they want to avoid following all other Code requirements.

We will see where the Code falls on this issue.

Best Regards

 

[vesselfab]

oh no no

if the vessel has a U stamp on it....
IT MUST meet all applicable requirements of the code

we can't just pick and choose which ones we should meet.

 

[doct9960]

U076762,

Is the statement of UG-125(a) not that clear to you?

 

[Arnieg]

I personally feel that wasting money, time, etc., installing relief devices on equipment that is inherently safe, (no credible over-pressure scenario / no liability), is a shame and reflects poorly on the engineering profession. It leads to contempt and ridicule. Unfortunately, I suspect that vesselfab has it right. ASME and NBIC have little use for reason and logic; keep it simple stupid. Fortunately, many local jurisdiction tend to be more reasonable and flexible than ASME & NBIC. I am very interested in hearing about the response UO76762 gets from ASME. I hope vesselfab is proven wrong but I wont hold by breath. The company I am working for requires strict compliance with ASME & NBIC . . . I an working on sizing,(ha ha), purchasing, and installing another s’ load of useless relief valves.

 

[metengr]

Arnieg;
First point; Regarding the NBIC, pressure relieving requirements default back to the original code of construction requirements. So, your comment below is more emotional than fact.

ASME and NBIC have little use for reason and logic; keep it simple stupid.

Any vessel can be designed to ASME B&PV Code, when it comes to applying the stamp ALL requirements must be followed. If you don't need to stamp the vessel for service, you can pick and choose requirements as you please.

 

[Arnieg]

The bottom line is that all too often we are working hard installing relief valves on systems that can not be over-pressured, (physically impossible). These relief valves will never lift due to an over-pressure situation. Sizing a valve that will never lift is a farce. These useless valves will have to be, tested, repaired and replaced. What a waste. Over-pressure protection by design makes sense in many applications, (piping code allows for it). Code case 2211 needs to be expanded to include all fluids . . .

 

[jte]

Arnieg-

Its all too easy to take potshots at a VOLUNTEER organization. About as easy as back seat driving and Monday morning quarterbacking. When you volunteer to carry the workload of a code committee member, apply, and are accepted to WORK on a committee, let us know.

I've been in your shoes with respect to installing pressure relief valves which seem to have no hope of actually lifting in their lifetime. As metengr pointed out, in many cases the way to go is to design and fabricate to VIII-1 but do not stamp.

It will indeed be interesting to see how UO76762's interpretation request proceeds. Any idea of whether it is being discussed at this week's meeting or is it expected to be discussed at the April meeting?

jt

 

[doberdorks]

The bottom line is that all too often we are working hard installing relief valves on systems that can not be over-pressured, (physically impossible).

I will add the comment that "you never know what changes the plant will make over the next 40-60 years"... so it may be in some cases that the relief valve is reasonably priced insurance.. but then again, the people who don't check if you need one for plant modifications also probably won't check if the existing one is correctly sized.

SLH