# 2001 Munich
Transco, part of the Lattice Group, is the largest Public Gas Transporter in Great Britain. It currently operates a Distribution system of some 250,000 kilometers. Developments in polyethylene pipe technology have led to an ongoing increase in the size of pipe being laid in the U.K. Currently, pipes up to 630 mm (PE80) and 400 mm (PE100) have been commissioned. The ability to maintain gas supply when undertaking flow stop operations on PE pipelines are essential. Flow stop operations are necessary :1 for planned maintenance and network extension and,2 to enable emergency repair as a result of damaged caused to the pipeline. Over the past 4 years Advantica Technologies Ltd (formerly BG Technology) and Transco have undertaken flow stop developments for application on large diameter PE 80 (up to 2 bar operating pressure) and PE 100 (up to 7 bar operating pressure) pipelines. Estimated cost benefit of these developments is £5,000 - £100,000 per operation.