Pipe Stress Analysis 4

[WindTree]

Hi

Why the momentum force due to change in the direction of the velocity (i.e. in a bend for example) is not considered for (or has it been considered in some manner?) in ASME B31.4?

Thanks in advance

 

[1503-44]

The pipe is welded so the pressure and momentum stresses will not pull apart the joints as it would a bell and spigot type joint. Both the momentum and pressure forces at elbows are balanced mostly by axial tension stress in the pipe wall.

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I take no responsibility for any damages or injuries of any kind that may result.

 

[LittleInch]

Unless the velocity is very high, these forces are often ignored as being insignificant.

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

 

[1503-44]

And it is safe to do so. A little tension in the axial direction is actually a good thing. Remember Mohr's circle. Hoop stress tension is 90° apart from axial tension, so both values fall on the same right hand side of the 0-stress vertical axis, thus the resulting max principle stress circle is much smaller than a plot of a compression stress point on the left side of the 0-stress axis would give. Max shear stress is actually less with two tension stresses.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[WindTree]

Thanks all for the responses

 

[Farhad1965]

Hi

Slug flow load due to change in momentum should be considered for all codes. Slug loading on an individual elbow, therefore, is generally only a single application load that can be readily treated in mechanical piping system analysis by the application of a Dynamic Load Factor, usually equal to 2.0.
Slug loads typically move through a piping system like water hammer and steam hammer loads but do not reflect from end boundary conditions.
See attached file for more detail.

Regards,
Farhad