As part of the on-going evaluation of the KOBUS Pipe Puller for implementation within their operations, AMEC Utilities invited KOBUS Services Ltd to undertake a pipe replacement to a private domestic property situated in a suburban area of Sheffield, Yorkshire. This work was part of the compilation of the data for the National Grid Field Trials documentation which would lead to National Grid Type Approval. Six pulls had previously been successfully completed as part of this process.
The pipe to be replaced was part of a larger project to replace some 14km of gas mains and service pipes in this part of Sheffield. The original town gas network was installed in the 1920’s with the construction of the Arbourthorne Estate and then upgraded in the 1970’s with the widespread introduction of North Sea gas into the UK market. These pipes are now life-expired with a record of significant small-scale leaks. Total network renewal is via a range of techniques, including insertion (for mains) and replacement, moling or open-cut for the smaller service pipes. (Note: in the gas sector service pipes are replaced to the customer property entry).
The section of pipe to be replaced was 3/4” galvanised steel, 14m in length. The pipe ran under the front garden and concrete to a side entry to the property. Thrust moling had been considered as a potential technical solution but the presence close to the gas main of significant quantities of services, including a HV power line and fibre optic cables, meant that the risks of services strikes were too great for a mole. The Pipe Puller was a suitable alternative technique as it would significantly reduce or eliminate the risk of any service damage or loss of the mole. Open-cut was not considered due to its greater cost and the presence of concrete.
The complete task of cable threading, Puller assembly and stabilisation, removal of the galvanised steel pipe and replacement with an MDPE pipe from the side of the house to the main took approx. 50 minutes. The actual pipe replacement itself took only 316 seconds. No further excavation was needed.
The work was undertaken under standard AMEC Utilities Pipelines health & safety procedures, which in this case also included the additional safety requirements for working close to underground HV power lines. There were no reported incidents in respect of either service strikes (HSG47) or operator activity.