New Standard BS 8701:2016 Full ring ovalization test for determining the susceptibility to cracking of linepipe steels in sour service. Test method

A new British Standards BS 8701:2016 was published last June, this standard addresses how to test for corrosion and environmentally assisted cracking in oil and gas pipelines. It revises of HSE guidance document OTI 95 635 which is referenced in ISO 15156.

Overview

BS 8701:2016 is a new British Standard on how to test for corrosion and environmentally assisted cracking in oil and gas pipelines. It is a revision of HSE guidance document OTI 95 635 which is referenced in ISO 15156, the flagship document for upstream material selection for sour service.

Who is the standard for?

The standard will be used by the manufacturers of pipelines that are designed to transport petroleum, petrochemicals and natural gas products.

What does the standard cover?

Sour service cracking problems in pipeline steels are caused by the presence of wet hydrogen sulphide (H₂S). This standard provides a protocol for ensuring such pipelines are properly tested to avoid environmental damage from pipeline failure.

The test method determines the susceptibility of pipeline steels, bands, flanges and fittings including all associated welds. It details an industry-proven technique for assessing pipeline steels by stressing a full ring specimen in a sour environment using mechanical means to deform the pipe by ovalization.

The test exerts a known stress level at two regions of a full ring section of pipe steel. The pipe specimen is then exposed internally to a sour test solution, although some cases require the sour media externally.

Ultrasonic monitoring and hydrogen permeation measurements are then conducted regularly during the exposure period. Both crack initiation and propagation can therefore be monitored. Finally a metallographic study of indications is undertaken to classify any defects found by the ultrasonic survey.