Southern Gas Networks (part of Scotia Gas Networks) has recently renewed a 3” steel gas riser in a four storey block of 45 flats in Southwark, London, using the Live Riser Transfer technique. This enabled the company to replace the service without turning off the supply, thus avoiding inconvenience for the consumer and reducing costs at the same time.
When compared with using conventional replacement methods, Live Riser Transfer delivered a substantial saving.The technique was developed by Steve Vick International and has been in widespread use around the UK for over a decade. SGN has begun to use Live Riser Transfer again following a recent review when the company decided that the cost savings offered are highly significant as long as the remaining pipe work passes a thorough examination.
To throw the riser dead would have meant turning off the gas supply to the 45 flats whilst the renewal was carried out. At the end of the procedure, the occupant of each flat would have had to be available to allow the supply to be purged and tested. Moreover, to provide a new steel riser on the outside of the building would have incurred the high cost of scaffolding.
The procedure was carried out over three days. On day one, a Steve Vick technician fitted and tested an under pressure tee on the riser where the new supply would be pieced in. The riser was drilled, in no-gas conditions through the tee via a flanged valve. The UPT was then encapsulated with a fabric collar injected with fire retardant material to provide a 30 minute fire check in accordance with GIS/SER6.
The following day, SGN’s pipe fabricators pieced in and commissioned the new 3” steel service. On day three, Steve Vick team carried out a flowstopping operation to the riser using the patented FOAMBAG™ method combined with a special angled under-pressure tee to allow the bag to be inserted and the foam injected in no-gas conditions. In conjunction with this SGN was then able to carry out a conventional flow stopping operation externally to abandon the riser under the building.
SGN purged the redundant section before the Steve Vick team filled it with expanding resin foam to ensure safety in the future.
The steel riser below the new supply was then cut and capped and a permanent prop installed to support the weight of the steel pipe above. A second collar injected with fire retardant material was fitted over the cap end on the live side.
In-depth approved survey
Enhancements have been incorporated into the Live Riser Transfer technique over recent years, including the provision of an in-depth survey prior to the project which involves both Steve Vick and the customer agreeing on all aspects of the riser renewal such as the exact positioning of the new service. At this planning stage, it may also be decided to fit a flexible coupler within the new supply as the thermal expansion of the steel pipe needs to be considered.
Drew Corrigan the Southern Gas Networks operative managing the Southwark job said, “To carry out this riser renewal in the traditional way – by installing a new riser on the outside of the building – would have meant cutting the gas supply to all 45 flats. We’d then have been faced with the problems associated with getting access to each flat for re-lighting. What’s more, the cost of scaffolding for such a job would have been huge.”
“We were very pleased with how straightforward the Live Riser Transfer procedure was and how quickly it was completed”, said Drew.
This project in London follows an earlier successful Live Riser Transfer carried out by Scotland Gas Networks in two block of flats in Glasgow where a total of 14 Live Riser Transfers were carried out.
Steel services, particularly sections under buildings, are frequently the cause of leakage. The Live Riser technique developed by Steve Vick allows operators to renew only that part of the riser which is damaged and leave the remainder in commission. The technique is cost-saving on many fronts and avoids disrupting the gas supply to consumers.
Steve Vick offers Live Riser Transfer as part of its Special Contract Service providing experienced technicians and all the hardware required for the procedure.
Date published – 11th December 2011