pipe weldment question

Date 04-12-2006 16:54

Assuming your contract with the subcontractor does not require the shop to have a PP or S stamp; I believe the answer to your question is contained in ASME Section VIII, U-1(c)(2)(e) - (not included in the scope of the code, therefore, no code authorization is required for the part you describe):

"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."

Basically, you have described quite well what your pressure vessel is. Referring to U-1(e)(1)(c), you see that the flanged face of the first flanged joint (on the pressure vessel side) is the boundary.

The spool piece you describe attaches to that joint, and is "generally recognized as a piping component". To repeat myself, no code stamp is required for the manufacture of that part.

Although the spool piece manufacturer does not have to possess an ASME stamp, if they are producing a spool piece for use on a pressure vessel skid for you, you have the right to reject the component if it fails weld quality acceptance criteria established by your contract with them.

Charles

By Bill M

Date 04-12-2006 17:06

Thanks Charles,

I agree with you that ASME Sect. VIII does not cover the piping.

But when does say, ANSI B31.1 or the ASME Power Piping certificate of Authorization stamp (PP) become a requirement for pressure piping?

By chall

Date 04-12-2006 17:25

B31.1 is for power piping. The general boundary for Boiler External Piping (code stamp required) picks up where the Boiler Proper (A or S stamp required) stops. It goes out to various locations depending on the number of boilers and/or feed water supplies. Where it stops, Non-boiler External Piping starts (no code stamp required).

To my knowledge the only situation where code stamped piping attaches to Section VIII pressure vessels is when the pressure vessel is an HRSG component. I've actually been on a new construction (HRSG) project where some of the modules were designed and built in accordance with ASME Section I, and some were done in accordance with Section VIII (S and U stamped components in one HRSG). It was very strange. We wound up treating all the interconnecting piping as though it was attached to a Section I component as it was more conservative.

If you send me an email, I will send you a scanned drawing that shows the breakpoints for the various classes of boiler components and piping (BP, BEP and NBEP).

Charles

edit comments: I should give you a caveat that depending on where you are located, there may be State laws or rules that dictate more stringent requirements. If you go to your State or Province Department of Labor website and search around for pressure vessel laws, it should help you find out if there are any local requirements that supercede the ASME guidelines.

By Bill M

Date 04-12-2006 17:42

thanks again,
I certainly appreciate your response to my inquiry!

By tito

Date 04-12-2006 18:30

Generally the piping componant that is attached to the code (U) stamped vessel would fall under B31.3 Process Piping. But this would only be required if spelled out in contract documents or other specifications. B31.3 is a code, but does not require or have a "symbol" for stamping purposes. In brief, if it shall be built to B31.3, the welders shall be qualified to ASME sec IX and work from a WPS. There is also weld inspection criteria depending on the process category, from a visual up to 100% RT. In all cases, the pipe shall be hydro or pnuematic tested to assure leak tightness.

In any case, you have the right to reject anything from your vendor...it's just easier and more justifiable if the requirements are laid out up front.

By G.S.Crisi (****)

Date 04-12-2006 19:59

I'll make a comment on your statement that "There is a short piece of pipe etc. The pipe is a 90º elbow with a butt weld flange on each end".
No flexible joint to absorb the compression vibration? Even the centrifugal compressors vibrate, to say nothing of the recips.
Did you never feel the need for a flexible joint ? I'm surprised.
Welds subjected to continuous vibration tend to show cracks in the long run.
Giovanni S. Crisi
Sao Paulo - Brazil

By Bill M

Date 04-12-2006 20:59

You are correct sir, I apologize for neglecting to report on the vibration dampening flexable joint in the line there. Hard to get something past you guys.