Gewebeschlauch-Rehabilitation von Gas-Hochdruckleitungen im Druckbereich bis 30 bar. Diskussion

In low-pressure gas distribution, grey cast iron pipelines dating back to the early days of gas supply have been rehabilitated successfully and economically for more than 15 years using fabric-reinforced liners according to DIN 30658-1 [1]. This technique allows spigot and socket joints packed with hemp and lead to be permanently sealed while also compensating the brittle pipes' susceptibility to failure, because even if there is a pipe rupture the integrity of the lined system is retained. Given the positive experience with these liners in low-pressure systems, it seemed reasonable to try to also rehabilitate the high-pressure steel pipelines installed since the beginning of long-distance gas transmission, which have been weakened over time by external corrosive attack. To this end, material tests were performed to characterise the strength of the liners and adhesives used and determine their resistance to media. These tests were accompanied by internal burst pressure tests and long-term internal pressure tests on lined pipes with defined defects. Field tests on lined pipeline sections were also conducted to study liner behaviour during depressurisation.While the material tests focused primarily on the components (i.e. the reinforced liners and adhesives), the investigations on the lined test pipes and pipeline sections were intended to examine the overall system comprising the pipe, the adhesive, and the reinforced liner, including all steps of the actual rehabilitation processes itself.An additional study on the development of external corrosion was to confirm the durability of the lined pipes.The project started with a total 6 relining processes. Two of these, which had been modified on the basis of interim test results, eventually met the requirements for a pressure range up to 30 bar and an intended service life of up to SO years. With the DVGW test procedure VP 404 drawn up, two DVGW-registered reinforced liner systems for high-pressure gas pipeline rehabilitation became available.