ASME B31.3 Non Metallic Piping Allowable Stress

[stanier]

I have been reading the standard and Charles brecht Process Piping (edition 1 covers ASME B31.3 1999). Have any forum members used the standard for designing thermoplastic materials?

How does one equate hydrostatic stress to allowable stress and take into account the usustained stresses and occassional load stresses?

Is there a publication that covers this in more detail?

Is the standard committee working on reviewing this part of the standadrd?

Is there an ISO standard that covers this matter in more detail?

 

[DSB123]

stanier,
Suggest you have a look at BS7159 which is for GRP piping.

 

[bvi]

The value of HDS (hydrostatic design stress) is based on time dependent material properties and determined in accordance with ASTM D2837. This is used for pressure design.

ASME B31.3 does not adequately cover allowable longitudinal stresses due to sustained loads. I suggest using the HDS as the allowable longitudinal stress, but pay attention to the joints, in case they are of a design that is weaker than the pipe.

ASME B31.3 does not provide an increased allowable for occasional loads such as wind and earthquake in combination with sustained loads such as weight and pressure. On the other hand, no allowable is provided for the sustained longitudinal stress. But to be consistent with the Chapter VII approach to load variations, and I think consistent with what the paragraph on occasional loads appears to indicate, I would not used an increased allowable for wind and earthquake in combination with sustained loads.

 

[UKCats]

stanier

May I suggest you attend one of the B31.3 Meetings and ask the Group themselves. Our next meeting is Apr 4-6 in Charleston SC and then Sept 9-13 in Cincinnati OH.

What kind of thermplastic???

 

[stanier]

Hi UKCats

Its a little diffcult as I live in Sydney Australia but thanks for the invite.

The thermoplastics I have in mind include ABS, PE, PVDF, PP, PVC-U, & PVC-C.

The Australian standard AS 4041 Pressure Piping Code defers to ASME B31.3 for design and installation of thermoplastic pipe materials.