Pressure Test Exemption?

[Moersleutel]

Hi

We are manufacturing a water pipe stop (either a blank or a head welded to a weld neck App 2 flange) where a valve is removed and it is designed/manufactured to ASME VIII Div 1. The inner diameter is ~700mm and the design pressure is 3500 kPa. We want to follow the flange to head path, due to the massive blind that will be required otherwise.

Is there any way we can avoid doing a hydrotest?

Thanks

 

[jte]

Rudol-

Did I do the conversion right? The way I see it you are looking at around 510 psi or roughly 35 atmospheres at ambient temperature. With a ~700 mm id being roughly 24" nominal, I'd say you just go with a carbon steel CL-300 blind flange and forget about it. It'll be 2.75" or 70mm thk.

If you insist on a WN to head approach, first double check your VIII calc's to see how thick the flange will be. Chances are it is thicker. You'll save some weight with the head but gain some with the weld neck. More expensive to fabricate also. How often will the blind be removed? Will the folks in the field really benefit from your engineering efforts? Are you blinding both sides of the pipe where the valve is pulled? Do you have clearance? Are you building two of these? If so, why not bolt them to each other and hydrotest them?

If you do stick with a designed and manufactured per VIII-1 approach, the answer to your question is simple: "Design and fabricate, but do not stamp." Thus no hydro req'd per VIII-1. The piping code you're using may have a hydrotest exeption based on the fluid being water at (presumably) ambient temperature. Its easy enough to do two forms of NDE (say PT and RT) in lieu of the hydro.

jt

 

[robsalv]

Jte has covered it well. Blind flange seems fair enough.

I would NOT avoid the hydro, especially if this is a permanent install and givent that water at 3500kPa might as well be treated as a harmful commodity.

B31.3 section 345 has all the guff about hydro test and exemptions. If the hydro is truly impractical, then you could go the NDE option... however, I'd MT the prep and root pass and then RT and MT the final weld. Give some thought to the weld procedure to ensure the best chance of minimum defects.

Cheers

Rob

 

[GenB]

It looks to me that it is a PART and not a complete vessel.
if some other company will install they can hydro and you just supply the partial data report w/o hydro.
talk to your AI.
GB