Unlike B31.4, the stress check in B31.8 does not differentiate between restraint and unrestraint pipeline. Because of this, stress analysis for buried pipeline using B31.8 can produce favourable results which may not pass under B31.4.

I am very concern with using B31.8 for buried restraint gas pipeline. Is this code suitable for such application ?

Has anyone got previous similiar experience with with using B31.8 in buried restraint condition under high pressure and temperature?

Hello,

ANSI / ASME B31.8, Gas Transmission and Distribution Piping Systems, is the appropriate Code for the design of buried gas transmission lines (you may want to review the B31.8 Introduction and paragraph 802 regarding scope). Regarding temperature, B31.8 explicitly excludes from its scope piping with metal temperatures above 450 degrees F or below -20 degrees F. No single piping Code section can provide "rules" for every application. It is often necessary to supplement the information in the Codes with established good engineering practice to provide for a safe piping system for the intended application.

The design of structural analysis software for piping must closely follow the requirements of the Codes and should never presume to interpret the Code’s intent. CAESAR II can only implement in its algorithm the literal requirements found in the current section of the applicable Code. You may write an inquiry to the B31.8 Code Committee and reference is made to B31.8, Appendix O, Preparation of Technical Inquiries to the ASME Code for Pressure Piping, B31.

Regards, John.

Hello,

Another thought regarding modeling technique. It may be of interest to you to look at B31.1, Power Piping, Appendix VII, "Nonmandatory procedures for the Design of Restrained Underground Piping". The referenced Appendix will provide some guidance for one possible modeling technique that the analyst might consider using in an analysis model.

The design and analysis of the piping system is the responsibility of the engineer. The engineer must be satisfied that the analysis satisfies the intent of the applicable Code. If the engineer can agree that the boundary conditions described in the cited Appendix are appropriate, the technique can be employed in the model and the B31.8 "Code checker" can be invoked for the stress checking.

Just my opinion.

Regards, John.