Test pressure = which ( Sa / S) ???

[carthago]

Assume we have a vessel with non standard bolted flanges ( girth ones).
Thus the vessel has heads, shells, nozzles, flanges and bolts.

The design pressure is is (P)
each item has its own (MAWP)

for each item the allowable stresses per Code: Sa (ambient) and S ( design) are
determined and their ratio is listed .

ratio for each item = Sa / S => 1


ASME , VIII div. 1 , UG -99B gives the minimum test pressure as

P_test= 1.3 * (MAWP) * minimum ratio ( Sa/ S)

or to keep simple:

P_test= 1.3 * design pressure (P) * minimum ratio ( Sa/ S)




In my case the minimum ratio (Sa / S) is the one for bolting !!

The question do we have to use the ratio (Sa/ S ) of bolting or not !

Or do we have to take into account (Sa/S ) of items "with membrane loading" (e.g. shells, heads, nozzles) and exclude bolting of any kind?

What is the MAWP of a bolt then ?????

Note:
Brithish code PD5500 , states for standard test pressure "...applied to vessel components sujected to membrane loading"
Same for the German Code.
The French code uses the maximum ratio (Sa/ S)
The European code includes non standard bolting

 

[eliebl]

Common practice is to use the stress ratio for the bolts.

EJL

 

[SnTMan]

carthago, in the absence of any specific customer requrements to the contrary, it is fairly common practice to let the lowest Sa/S govern this calculation, and often it is the bolting. UG-99(b) states "for the materials of which the vessel is constructed".

Some specs consider body flange bolting as a "minor component", I do not.

The MAWP of the bolting is the pressure at which A(reqd) equals A(actual). It may be higher or lower than the flange pair MAWP.

Regards,

Mike