Method of Preparing a Pipe-Section

摘要

A method of stress relief heat treating a pipe-section (which may be partly or fully seam-welded) 30a to be welded to another pipe-section to form a pipeline, comprising; i) providing a pipe-section having first 32 and second 34 pipe-ends; ii) defining a first portion L1 of the longitudinal length of the pipe-section from the first pipe-end, being in the range 3% to 40% of the overall length of the pipe section; iii) defining a second portion L2 of the longitudinal length of the pipe-section from the end of the first portion L1 towards the second pipe-end (or optionally to the end of the second pipe-end); iv) heating at least the first portion L1 to at least a first temperature T1 of at least 500oC for at least two minutes and v) maintaining a second temperature T2 of the second portion L2 during step iv) below the first temperature T1. The method may also involve defining a third portion L3 of the longitudinal length of the pipe section, and defining the second portion L2 as the intermediate longitudinal length between L1 and L3, and heating L1 and L3 (which may be performed simultaneously or sequentially) to at least the first temperature T1 for at least two minutes and maintaining the second temperature T2 of the second portion L2 below the temperature T1. T1 may be in the range 600-1000oC. The resulting pipe-sections may be suitable for reel-laying into a sea environment from a vessel, to form a pipeline.