ASME PCC-1 Appendix O

[DigDug.]

Hi Guys, I've been tasked with creating a torque table for bolting flanged joints, and I have used the Joint component approach (O-4)to determine the required bolt stress.

We use standard B16.5 flanges ranging from 1/2" to 24" NPS, and classes 150,300 and 600.

I have made an excel calc sheet to make it easier changing the torque table values when a different gasket type or bolt/flange material is required.

I'm having a problem with checks 5 & 6 (5. achieving gasket seating stress and 6. achieving operating gasket stress) on most of the pipe sizes in the 150 class, and a few in the 300 class too.

I don't see a way that I can get the checks to pass for all the pipe sizes & classes.

Has anyone had experience with using the calcs in PCC-1? Did you run into similar problems, or is it likely that I have done something wrong? I'm quite confident that my calc sheet is sound, and I have uploaded it here for your viewing.

The input variables, along with the checks are on the PCC-1 worksheet.

Any help at all would be greatly appreciated.

Cheers,

DigDug

http://files.engineering.com/getfil...9f0f498fd&file=asme_VIII_calc_sheet_rev2.xlsx

 

[DigDug.]

I have just came across this paragraph in the code:

"Note that for some flanges (NPS 8, class 150 for example)
the additional limits [eq. (O-7) onward] are not
satisfied. In those cases, engineering judgment should
be used to determine which limits are more critical to the
joint integrity, and the value of Sbsel should be modified
accordingly. It should be noted that the values presented
are not hard limits (i.e., flange leakage will not occur if
the gasket stress falls 0.1 psi below the limit) and therefore
some leeway in using the values is to be considered
normal."

I suppose this gets my out of requiring passes on the checks I speak of, however won't this mean that my joint will leak? I'm so close to the yield of the bolt material already (at ambient temp!)

 

[XL83NL]

I havent checked your calcs, but based on your findings it seeems youve run into the problem with Cl150 flanges thats been addressed in the industry before.
Some flange design are wrong by design checks, i.e. cant pass the calculations. Warren Brown has written a few interesting papers on this subject. I recommend you get a copy of e.g. PVP2013-97813.

 

[XL83NL]

Ive reviewed your excel sheet again and Im quite impressed with the simplicity youve made to do calculations which are often considered complex. Any chance to share some mutual insights on your program?

 

[DigDug.]

Sure! Have you a particular calculation or assumption that you would like me to discuss?

In terms of given data in the sheet, It'd be more accurate if I could get the gasket operating, seating and crush stress values from our gasket manufacturer.


This task was born from the need to change our standard torque values, as a different anti-seize paste was specified by our customer which would've caused overloading of the bolts.

Initially I think it was expected that I would just need to fix the table with a correction factor. However, When I looked into it I couldn't find any reference to find where the initial values came from. Not only this, but the table never differentiated between flange classes or bolting material. It was simply, 'what is the bolt dia?, 45k or 60k bolt stress?, here's your torque value###'