ASME 1 Vessel 5

[jayinwww]

During inspections we found that flanges off the vessel were off by 3 degrees. The manufacturer says it is fine. But we do not think so. Is there anything in ASME 1 that states clearly the tolerance or do we have to go off of b31.1.

 

[XL83NL]

1. A vessel to ASME 1? You mean ASME Section I (which is for power boilers), or sec VIII-1?
2. Which section(s) of the applicable Code have you checked so far that didnt help you find your answer?

 

[r6155]

See Process Industry Practices PIP VEFV 1102.
The manufacturer must show that it is ok.

Regards

 

[XL83NL]

See Process Industry Practices PIP VEFV 1102.

Thats not the question (regardless if PIP practices could be useful on some cases):

www]Is[/URL] there anything in ASME 1 that states clearly the tolerance

 

[JStephen]

Is that out-of-plumb by 3 degrees? Or rotated about the axis by 3 degrees?
And is this a mating pair of flanges that are both rotated, or a nozzle that needs to bolt to something else that is presumably plum?
It might be informative to calculate stresses in the pipe required to fit things up.

 

[r6155]

Nozzles and Attachments Elevation, nozzles and attachments levelness tolerances, etc., etc are not addressed in ASME Code

The Code is not a handbook.

The Code does not fully address tolerances. When dimensions,sizes, or other parameters are not specified with tolerances, the values of these parameters are considered nominal, and allowable tolerances or local variances may be considered acceptable when based on engineering judgment and standard practices as determined by the designer.

Regards

 

[Christine74]

What tolerances did you specify when you purchased this vessel? Whenever you purchase an ASME Section VIII pressure vessel you have to specify the allowable tolerances for the nozzles. If you didn't specify any tolerances, your nozzles could be off by 30° and the vessel would still meet Code.


-Christine

 

[r6155]

With a responsible manufacturer it is not necessary to specify dimensional tolerances.

Regards

 

[boofi]

ASME PCC-1 "Guidelines for Pressure Boundary Joint Assembly" Appendix E has some guidance for flange alignment tolerances. The BPVC does not contain anything regarding flange alignment as far as I know. In which direction is your flange off by 3 degrees?
[ul]
Centerline High/Low: 1/16" max misalignment[/li]
[li]Flange Faces Parallel: 1/32" max difference between widest and narrowest gap (no "birdmouthing")[/li]
[li]Rotational two-hole:1/8" max[/li]
[li]Excessive spacing/gap: should be self explanatory[/li]
[/ul]
I should also note that these guidelines are for joint assembly; it is not necessarily design guidance.

 

[MJCronin]

This should have been discussed and detailed by both the customer and the fabricator in the purchasing documents!!

Questions like these .... AFTER FABRICATION .... is the direct result of hiring new engineers (because they are cheap) and not having experienced staff available.

Just one question for the OP .... Is this your first pressure vessel ????

MJCronin
Sr. Process Engineer