Piping design limits

[pipe15]

ASME Section III pipe has Level A, B, C, & D conditions. As I understand, the level A are labeled as Design Pressure and Design Temperature.

ASME B31.1 defines Design Pressure and Design Temperature as the maximum sustained operating pressure (MSOP) at the maximum sustained condition temperature.

Both of the above have methods to evaluate the pipe components for other than normal operation (that may exceed the design conditions) using higher stress allowable values.

Now lets say I have a flanged component. Do the maximum allowable working pressure values in B16.5 govern for setting max pressure for the design of a piping system that contains flanged components? It does not appear that B16.5 allows you to exceed the values in the various material group tables.

So it seems that an all welded system and a system with flanged components would have different qualification limits.

Am I missing something?

Thanks

 

[BigInch]

Flange allowable working pressures can be increased by the same corresponding percentages for temporary overstress and for testing conditions when permitted by code.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Greg1920]

Flanges and Valves temperature pressure limits generally govern what the design temperature / pressure limits of your piping classes will be.

As stated above the temporary increase in pressure or temperature permitted in B31.3 are also allowed for all the fittings/flanges/valves permitted in B31.3.

 

[davefitz]

this may be quibling, but valves are designed to b16.34, and its paragraph 2.5.1 only allows for a max overpressure not in excess of 10% over the published pressure-temperature ratings . It specifically states that overpressure during relief valve events or hydropressure above that 10% overage is solely at the users risk.

 

[BigInch]

That's exactly why there are things like API-6D

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[pipe15]

I do not see in B31.1 or B16.5 where flanges are allowed to exceed the published allowable working pressures. B31.1 (2004)says:
It is recognized that variations in pressure and temperature
inevitably occur, and therefore the piping system,
except as limited by component standards referred to
in para. 102.2.1 or by manufacturers of components
referred to in para. 102.2.2, shall be considered safe for
occasional short operating periods at higher than design
pressure or temperature. For such variations, either pressure or temperature, or both, may exceed the design
values if the computed circumferential pressure stress
does not exceed the maximum allowable stress from
Appendix A for the coincident temperature by
(A) 15% if the event duration occurs for no more than
8 hr at any one time and not more than 800 hr/year, or
(B) 20% if the event duration occurs for not more than
1 hr at any one time and not more than 80 hr/year

it seems flanges are the limiting component.

also as I understand, B16.34 has standard class tables, special class table and also the Intermediate Rating Class Method. B16.5 does not allow this type of thing and would always point the user to the standard table values for a flanged valve.

 

[BigInch]

I don't have B31.1. What does 102.1 & 2 say?

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[pipe15]

a bit long but here goes..
102.2.1 Components Having Specific Ratings. Pressure-
temperature ratings for certain piping components
have been established and are contained in some of the
standards listed in Table 126.1.
Where piping components have established pressure temperature ratings which do not extend to the upper
material temperature limits permitted by this Code, the
pressure-temperature ratings between those established
and the upper material temperature limit may be determined
in accordance with the rules of this Code, but such
extensions are subject to restrictions, if any, imposed by
the standards.
Standard components may not be used at conditions
of pressure and temperature which exceed the limits
imposed by this Code.
102.2.2 Components Not Having Specific Ratings.
Some of the Standards listed in Table 126.1, such as those
for buttwelding fittings, specify that components shall
be furnished in nominal thicknesses. Unless limited elsewhere in this Code, such components shall be rated for
the same allowable pressures as seamless pipe of the
same nominal thickness, as determined in paras. 103
and 104 for material having the same allowable stress.
Piping components, such as pipe, for which allowable
stresses have been developed in accordance with para.
102.3, but which do not have established pressure ratings,
shall be rated by rules for pressure design in para.
104, modified as applicable by other provisions of this
Code.
Should it be desired to use methods of manufacture
or design of components not covered by this Code or
not listed in referenced standards, it is intended that
the manufacturer shall comply with the requirements
of paras. 103 and 104 and other applicable requirements
of this Code for design conditions involved. Where components other than those discussed above, such as pipe
or fittings not assigned pressure-temperature ratings in
an American National Standard, are used, the manufacturer’s
recommended pressure-temperature rating shall
not be exceeded.

table 126.1 list the standards (16.5 for instance) plus many others

thanks

 

[BigInch]

Where piping components have established pressure temperature ratings which do not extend to the upper
material temperature limits permitted by this Code, the
pressure-temperature ratings between those established
and the upper material temperature limit may be determined
in accordance with the rules of this Code,
-------------------------
I'd suggest that you check the flanges using the flange material's limits as defined in B31.1




**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/