Northern Gas Networks (NGN) has a population of sleeves on its Local Transmission System (LTS) High Pressure (HP) network, historically these were installed as additional protection for road, rail and river crossings and are typically constructed of larger diameter steel pipe with the carrier pipeline requiring protection inserted through. Sleeves with a vacant anulus can cause a significant issue for pipeline integrity as the internal environment can become corrosive, increasing risk to the HP pipeline. Remediation for vacant sleeves is to fill the annulus with grout, protecting the pipeline from corrosion and other issues. A historic data issue with sleeves is that the fill material is unknown, posing a potential risk that these sleeves may be vacant and compromise the integrity of the carrier pipe.
At present the only means of determining fill material for a sleeve is deep excavation at both ends and drill into the sleeve end seals to visually assess. This is expensive and time-consuming work that is not feasible for network wide application.
NGN would like to understand if there is a means of determining sleeve fill material with a less invasive / lower cost technology?