Introduction: A Reliability Centred Maintenance (RCM) process highlighted a potential hidden mode of failure associated with cold winter temperatures (water ingress and freezing conditions) during the operation of Remotely Operated Valves (ROVs). Current statistical analysis implies that reliability of these ROVs is 99% (i.e. 1% fail to operate upon instruction from the Gas Network Control Centre (GNCC)). However the majority of valve tests take place during summer months, therefore a number of possible modes of failure associated have been previously un- accounted for.

There are 828 ROVs on the network in total but physical testing of each combination of component making up any one system is unfeasible due to the number of each type of valve, actuator, gearbox combinations. This project therefore looks to initially assess the scale of the problem (if in fact there is one), with physical testing of any components an option at a later stage, together with development of design modifications to mitigate the potential risks.

This project will develop a geographical profile for the risk of persistent severe winter conditions in the vicinity of the National Transmission System (NTS). The risk profile will be illustrated in the GIS-enabled package, Uptime, which already holds information of the location of AGIs, their high-level function and individual isolation valve references.

Objectives:

This project will deliver a risk-based approach for the prioritization of retrofit measures to address isolation valve reliability during periods of sustained severe winter conditions.

Expected Benefits: The project will be considered successful with the delivery of a geographical profile using the GIS-enabled package Uptime for the risk of persistent severe winter conditions. The project will provide a number of additional new attributes to the AGIs detail in Uptime.