Pressure Induced Moments on Elbows

[denniskb]

Is there an overall bending moment apllied to an elbow by the internal pressure?

If so is there a generally accepted calculation of this moment for different elbow angles?

We are doing stress analysis of GRE pipelines where the moment capacity of the elbows can be calculated to ISO 14692 but this calculation does not reflect a moment component from the internal pressure.

Dennis Kirk Engineering

http://www.ozemail.com.au/~denniskb

 

[richay]

Is there an overall bending moment apllied to an elbow by the internal pressure?
No. In a typical flexibility analysis, pressure does not cause displacements or loads on the pipes. Pressure is considered in the stress computation in the form of the longitudinal pressure stress term. There are a few exceptions to this statement. Some transportation codes include hoop stress, an expansion joint may cause pressure thrust loads, and you can always turn on Bourdon pressure effects.

If so is there a generally accepted calculation of this moment for different elbow angles?
Not that I am aware of.


Typically for GRE piping systems, you would want to turn on Bourdon pressure effects. This will introduce a strain on each pipe element. Forces and moments will be developed as a result of this strain and the finite element solution.



Richard Ay
COADE, Inc.