Steve Vick International’s (SVI) Contract Service team have renewed ten 1.5” live gas risers in multi storey buildings in an affluent suburb of Leeds, without the need to decommission the services whilst the work was in progress.
Using their Live Gas Riser Transfer technique, SVI were able to offer Northern Gas Networks (NGN) a service that kept external pipework to a minimum and thus protected the aesthetics of the building.
Live Riser Transfer allows a section of old service entering under the building to be partly renewed or transferred to a new main without first throwing it dead. It is hugely beneficial in multi-storey, multi-occupation housing as it avoids the need to gain access to each dwelling to turn off and relight the gas and avoids disruption to consumers’ supplies.
The properties involved included three 3 storey buildings. As part of NGN’s mains replacement programme, the feeder main to the properties was being renewed which required the risers to be transferred to the new PE main.
Using a combination of under pressure tees, under pressure drilling equipment and valves, SVI’s technique allows a new service to be pieced in and commissioned. In order to abandon the old section of riser, an angled under pressure tee is fitted below the new service and is drilled to allow a FOAMBAG™ to be installed.
A conventional flow-stopping operation is performed outside the building by the Gas Distribution Network to enable the redundant section to be purged and tested. The entire abandoned section of service may then be filled with foam to ensure safety in the future. The steel riser below the new supply is cut and capped and a permanent prop is installed to support the weight of vertical risers.
To comply with GIS/SER 6, the under pressure tees and live end caps are encapsulated with a fire retardant material.
Russ Oxley, Construction Services Area Manager at NGN said, “Using a traditional method of riser renewal would have generated the problems associated with gaining access to each flat for re-lighting. By using the SVI Live Riser Transfer technique we were able to avoid using external pipework and reduce disruption to customers. We were highly satisfied with the service and support provided by SVI and we were very pleased with how straightforward the Live Riser Transfer procedure was.”