ASME B31.8 VS CSA Z662


ASME B31.8 VS CSA Z662 by Meena Rezkallah, P.Eng. for engineering Services across Canada and USA.

This Article focuses on the comparison of the American Society of Mechanical Engineers (ASME) B31.8, Gas Transmission and Distribution Piping Systems and the Canadian Standards Association (CSA) Standard Z662, Oil and Gas Pipeline Systems. Significant issues which are expected to be the basis of continued discussion include:

  • Increasing the design factor in Class 1 locations in the US to the Canadian value of 0.80

  • Allowing additional flexibility in valve spacing

  • Normalizing requirements for pressure testing, especially hydrostatic testing

  • IM requirements.

There are also differences in depth-of-cover requirements, although they do not appear to be a critical factor.

Both standards incorporate concepts of strain-based design and reliability approaches, although no consensus has been reached on a standard approach for pipeline design or operations. In this regard, a prescriptive approach would likely be counterproductive and an application methodology might be a better option. CSA Z662 Annex O provides a reliability-based methodology that can be applied to both design and operating scenarios for gas pipelines. The methodology establishes definitive target levels of reliability. ASME B31.8 is expected to publish Reliability Based Design and Assessment methodology in December 2008 which is reportedly based on the same reference material as Annex O; however, detailed information was unavailable at the time of this report.

Table below provides a tabulated version of comparisons between US and Canadian gas transmission pipeline design.

Read more:

  1. ASME B31.8 VS CSA Z662

  2. ASME B31.4 VS CSA Z662

  3. ASME B 31.1 & ASME B 31.3 CODE COMPARISON

  4. ASME B31.3 (Power Piping) VS ASME B31.3 (Process Piping)

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