Occasional load for flange

[CesarYalan]

Dear All,

I want to determine the maximum allowable pressure of a piping system, firts fir the pipe i have been determined the maximum pressure for sustained and occasional loads according with ASME B31.3. Now for flanges i am not sure if the maximum allowable flange pressure indicated by ASME B16.5 includes occasional loads or i have to multiply by 1.33.

I would apreciate your help.

Regards,

César

 

[XL83NL]

Occasional, sustained and MAWP are three different things. The latter does not include gravity and is typically covered by, e.g., B31.3 para 304.
The first 2 are checked typically using pipe stress analysis.
For Occasional loods, yes, B16.5 flanges also are checked with a factor of 1.33, but that factor applies to the load, not the (max allowable werking) pressure.

 

[XL83NL]

Ps: there's one circumstances where a B16.5 flange may be overstressed due to pressure, see here;

http://eng-tips.com/viewthread.cfm?qid=369092

 

[opinion1055]

CesarYalan

First of all, you cannot choose a pipe to withstand sustained load and occ. load.
You have to design your pipe based on its process parameters and design basis and fix it.
Then you stress analyse the system to make it good enough to withstand sus. Load and occ load.

Maximum allowable pressure of the material of pipe at design temp, you can get from ASME B31.3 (for process piping), TABLE-A

"Maximum allowable flange pressure indicated by ASME B16.5 includes occasional loads or i have to multiply by 1.33"..... Max. allowable flange pressure indicated by ASME B16.5 is what it is.

Multiplication by 1.33 is an "Occ. load case check" as per ASME 31.3 code.


Hope this answered you

 

[XL83NL]

well repeated, except;

Maximum allowable pressure of the material of pipe at design temp, you can get from ASME B31.3 (for process piping), TABLE-A

Table A-1 is used for calculating the minimum required thickness acc. the Base Code. Table A does not list allowable pressures, it lists stress allowables.

 

[opinion1055]

XL83NL, Yes you are right. Its my mistake.

The max. allowable pressure can be obtained from B16.5 Flange rating table....Am i correct. ?

 

[XL83NL]

For flanges, yes.
For pressure design of piping components, see B31.3 para 304.

 

[CesarYalan]

XL83NL and opinion1055,

Thanks a lot for your answers, i understand that Occasional, sustained and MAWP are three different things, but i just wanted to know the MAWP for a flange. I mentioned occasional and sustained, because i calculate the MAWP acording with ASME B31.3 considering stress of Table A-1(SUSTAINED) and for ocassional stress multiplied for 1.33 and calculate the maximum pressure allowable for ocassional load, but according with your answers those calculation are wrong, am i correct???

Thus i wanted to know the MAWP for a flange in order to determine the maximum allowable pressure of a piping system, so pipe, flange and fitings.

So it is clear that the MAWP of flange are indicate in ASME B16.5.

 

[XL83NL]

Just so we tot this clear: the MAWP for a flange is that pressure as listed in B16.5 for the respective material.

 

[Duwe6]

. . . the MAWP for a flange is that pressure as listed in B16.5 for the respective material at the maximum allowed operating temperature - MAWT