Nov 2016
Gas Transmission
Permanent PE slab protection
Nov 2016
Mar 2019
National Grid Gas Transmission
Paul Ogden
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Network Innovation Allowance
GT - Reliability and maintenance
Gas Transmission Networks
Increasing occurrences are being identified of longer lengths of pipeline e.g. 50m+ in field situations where the pipeline has a shallow depth of cover (DOC) e.g. 0.9m or less. In some cases the DOC has been found to be 0.5-0.6m in fields where ploughing can take place up to 0.45m deep. The number of solutions available to National Grid, to mitigate these risks are limited to; legal agreements to limit agricultural activity / buying land / relaying the pipeline / importing additional soil. All have significant costs or /and difficulties and frequently result in the loss of prime agricultural land.

As a result of an earlier innovation project the use of PE slabs has successfully been implemented as an impact protection measure for NTS pipelines which cross ditches at a shallow depth. The idea has emerged of manufacturing the lightweight PE sheets in a pre-formed ‘upside down U shape’ at a diameter of e.g. 100mm larger than the pipeline, which could be installed over the pipeline where DOC is a problem. The field trials would need to examine the worst case scenario of deep ploughing hitting the PE sheet with a view to deflecting the ploughshare such that it rides over the slab. Ploughs riding over obstructions is a relatively ‘normal’ occurrence when hitting stone slabs etc. that ploughs sometimes encounter in fields.

To develop an approved method for the use of shaped PE lightweight slabs fitted over shallow pipelines in fields so as to provide a degree of protection from third party damage from agricultural activity.

An approved method accepted for use by National Grid in clearly defined and appropriate circumstances.