The regional gas transmission network of Gasunie Transport Services in the Netherlands consists of roughly 3000 km pipelines, 3000 valve stations, 75 pressure regulating and metering stations and 1100 gas receiving stations. Because the majority of these stations was built in the period 1960–1980, questions have arisen regarding their remaining technical lifetime and which measures should be taken to comply with future safety and transport standards. In the Gasunie Network Improvement Program (GNIP), these stations are replaced completely, prioritized on their expected condition.
By supplementing the GNIP Verification Project (GVP) to the GNIP, a “Plan-Do-Check-Act” circle was introduced to identify improvements from executing the GNIP. In the GVP, lifetime critical parts of the replaced stations are inspected by specialized companies, in-situ as well as in their laboratories, to assess their actual condition. The lessons learned and results from the GVP have led to adjustments in the replacement program in terms of both scope and pace.
This paper gives a general overview of the GNIP and the GVP. The results of the GVP are then presented with a focus on the condition of gas delivery stations, particularly the condition of components that are not or poorly accessible during normal operation, such as headers and wall crossings. The actions taken by Gasunie to adjust the GNIP based on the GVP outcomes will be discussed.