Those involved in the design and installation of new polyethylene pipeline networks and more specifically, those with a keen focus on the commissioning end of the process – the part which validates that a new pipeline installation is leak-free and fit for purpose – have much to focus on this year.
Last month we got to see the latest updates and changes to IGN 4-01-3, the go-to advice and guidance note for the installation of Polyethylene pipelines. The IGN not only sees its first major update in ten years, but also its elevation in authority to a WIS.
There are plenty of tweaks to the old IGN and a substantial change in the reduction of maximum allowable air content – at any stage of the test – from 8% to 4%.
Removing most of the air from a pipeline before testing is critical for several reasons, none more pressing than to ensure safety. The stored energy contained within any pockets of air trapped within a system can easily reach levels where risk-to-life accidents are a significant possibility. Removing this air mitigates the risk as far as practically and reasonably possible.
An important safety enhancement of the WIS is the prescription that calculations required to ensure that the upper air content limit (4%) is never exceeded during testing must be completed before testing starts and not during it. This was previously a grey area and effectively meant that the pressurisation phase could already have started before the necessary air content checks had been made, the system then potentially exposed to the possibility of excessive – and dangerous – levels of air at high pressure.
The second reason is to promote efficient and accurate testing including test certification. The more air that is removed, the quicker and more accurate the testing becomes with all the associated benefits of test result accuracy, certification and cost savings achieved through shorter time cycles.
The implications of a reduced allowable air content are now more relevant than ever when the design and layout of the various elements that form a pipeline are considered. ‘How to remove air at the testing stage …’, is not always an obvious question that appears on the designer’s check list and there have been many instances when the removal of air is just not possible, meaning that achieving a legitimate hydrostatic pressure test certificate is rendered a virtual impossibility with all that that implies. There are other new requirements too, such as the higher specifications required for various pieces of test equipment and their calibration.
Without doubt the greatest consequence of the changes to the WIS is the reduction in permissible air content through the duration of the test. This is timely coming as it does just ahead of last week’s publication by the HSE of the results of its investigation into the explosion at Cropston in 2022 that caused serious injury.
Next up for publication are the results of UKWIR’s project, ‘Assessing the levels of leakage on new polyethylene networks, where, it must be hoped, recommendations complement the new WIS and further reduce the likelihood of another Cropston.