Limit States Design for Onshore Pipelines: Designing for Hydrostatic Test Pressure and Restrained Thermal Expansion

Abstract

Reliability-based design rules have been developed for the key serviceability limit states applicable to onshore pipeline including local buckling due to thermal expansion and excessive plastic deformation under hydrostatic test pressure. The design rules are characterized by three elements: the formulas used to calculate the characteristic demand and capacity; the criteria used to define the characteristic values of the key input parameters to these formulas (such as diameter and material strength); and the safety factors defining the required excess capacity over the demand.

The overall methodology used in developing the design rules and the practical implications of applying them are described in a companion paper. This paper describes the process used to calibrate safety factors and characteristic input parameter values that meet the desired reliability levels. The results show that local buckling under restrained thermal expansion is only potentially relevant for a small sub-set of cases and based on this, an explicit design rule was not developed. For excessive deformation under hydrostatic test pressure, two alternate design rules are provided; one stress based and the other strain based. The final design rules are described and an assessment of their accuracy and consistency in meeting the reliability targets is included. Guidance is also provided on the conditions in which each check is used.

Author: Adianto, R. H. and Nessim, M.A.

Publisher: 10th International Pipeline Conference, Calgary, Alberta, September 29 – October 3

Year: 2014

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