ASME B16.34 NDE

[MortenA]

When are you to use radiographic/ultrasonic NDE for ASME B16.34 valves?

ASME B16.34 groups valves into "standard", Special" and "limited" but im not sure that i understand how o group. Is this whats dealt with in sec. 2.1?

Best Regards

Morten Andersen

 

[vpl]

Hey Morten - maybe it's just that everybody's shut down over on this side of the big lake, but you might want to ask the question in the ASME forum as well. All my Code guys are gone 'til next year so I'm afraid I can't help. Hope you have a good Christmas anyway! Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[PAN]

A valve manufacturer used to informed me that radiographic examination is supplementray examination as shown in API Std. 598.

 

[keyardee]

Hi MartonA
Forget about any code or something.Use your common sense.A normal valve's integrity is checked by the "proof of the pudding"-hydro test of shell and seat.This test may or may not reveal any hidden flaw in the valve.Most of the valves inspite of these hidden flaws might work and perform their functions well.Some of the internal defects may not show themselves up in the simple hydro tests.If your usage is critical you try to be more cautious try to look into the future with all these NDE.The usage decides the degeree of application of these NDE.Compare a valve in your bathroom closet and a high pressure boiler;they are supposed to do similar jobs.Will you suggest the same type of tests for both these valves?

 

[bcd]

Hello Morten,

Great question that is frequently asked. The application of B16.34 is "under the jursidiction of the ASME boiler and pressure vessel code, Pressure Piping codes, and govenmental regulations." Since the scope of potential valve applications in this arena is very large, B16,34 does not cover all possible inspection requirements for cast pressure parts. As mentioned in a reply above, the inspection requirements for pressure parts retaining potable water are different than those for lethal gas. So in direct reply to your post, you must refer to the governing code or regulations to determine if inspection is required of the valve bodies.

Special class and limited class valves are rarely encountered. Both are limited to only threaded and weld ends. Flanged valves cannot be anything but standard class. In addition, limited class valves can only be 2-1/2 inch and smaller. Special class valves may have a slightly higher pressure rating with some NDT inspection. That is the only benefit. To add to this confusion, valves fabricated by welding (e.g., welding flanges onto a valve body), may require NDT if required by the ASME BPVC (refer to section 2.1.5 in B16.34).

On the practical side, the best check for body soundness is the hydrotest. It is very easy to get false indications or completely miss defects using recognized NDT techniques. And, each technique has its limitation on the type of defect it can reveal. The expression "test it like you use it" best describes this situation. I feel much more comfortable standing next to a valve that has been pressure tested than one that was only RT, PT, or UT inspected. So please don't belief that a body that has been RT, PT, and / or UT inspected is any better than one that has only been pressure tested.

Hope this helps.

 

[RXH]

It's pretty much what the others have said. Specify NDE when your application becomes critical. In our company, we typically specify sample XRay for castings in hydrocarbon service 4"x1500 and greater, or greater than 24" in any class.