Suitability of stop-off bags in gas grids up to an operating pressure of 5 bar (MOP 5 bar)

An isolation technology for a temporary gas supply interruption that is safe, cost-effective, and proved by a huge amount of sites were it was successfully applied: Stop off-Bags-Technology. According to the DVGW Codes this technology can be applied up to operating pressures of 1 bar. Regulations in other European member states allow the application for higher pressures as well. Based on a literature inventory and an expert discussion it was not possible to identify profound testing results that support the recommendation of this technology for higher pressures. Therefore, a R&D project was set up aiming to investigate whether it would also be feasible to use this method in pressure ranges up to 5 bar. These investigations were performed in close cooperation with GDF SUEZ in the frame of a GERG project. Based on the information obtained from the pilot construction sites that were surveyed, the laboratory tests carried out and an assessment of the results, the technology of stop off bag insertion is found to be fit for the purpose with the systems used in this DVGW R&D project. The system should however only be used by experienced staff who have been trained in using such systems. Irrespective of the positive assessment of this technology up to an operating pressure of 5 bar, further development efforts should be made to identify unfavourable pipeline conditions (severe dust deposits, cuttings and moisture) or to avoid these conditions (e. g. cuttings) more effectively in the future. This would further improve the safety level of this technology.