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# ASME B31.4 Equation 402.6.2 SI Units

## ASME B31.4 Equation 402.6.2 SI Units

(OP)
Hi All,

The axial stress in the above equation (=Fa/A) calls up the axial force (Fa) in Newtons while the pipe cross sectional area (A) is called up as cm2. The resulting longitudinal stress is supposed to be in MPa which it isn't.

Am I missing something here?

Thanks in anticipation.

### RE: ASME B31.4 Equation 402.6.2 SI Units

It certainly looks like there is an error here and it should be mm2.

All the imperial units end up the same (psi), but the metric ones are MPa and KPa which doesn't look right.

Might be worth a technical inquiry (see non mandatory appendix A of the code - right at the back)

Could be everyone just uses mathcad which automatically sorts it out, or Caesar....

LI

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: ASME B31.4 Equation 402.6.2 SI Units

(OP)
Thanks LI. Have sent a clarification request to ASME.

### RE: ASME B31.4 Equation 402.6.2 SI Units

(OP)
Hi All,

Need some clarificaion around what pressures to use for modeling in Autopipe.

Our pump operating pressure is about 340m (dead head 400m). The thermal relief valves setting is set at 400m (hydrocarbon duty).

What pressure should be used in the model in conjunction with the seismic loads?

### RE: ASME B31.4 Equation 402.6.2 SI Units

(OP)
ASME have issued an interpretation #17-1764 on the above query regarding area units for the SI version of Equation 402.6.2 in B31.4.... units should me mm2.

### RE: ASME B31.4 Equation 402.6.2 SI Units

A result!

Thanks for coming back and updating us all.

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Also: If you get a response it's polite to respond to it.

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