Over 2000 metres of large diameter gas mains have been renewed using the new Steve Vick Pipe Handler in Attercliffe Road, a busy two way street in Sheffield. During the development stages with National Grid, they used the Live Mains Insertion technique to insert the pipe, ensuring customers and business owners experience minimal disruption during the operation.
The Pipe Handler
Steve Vick International recently launched The Pipe Handler as a safer alternative to winching or using an excavator bucket and sling to insert pipe. The device attaches to an excavator offering a new, efficient, safe way to pick up and manoeuvre PE pipe on site. At the same time, The Pipe Handler is capable of inserting long lengths of PE pipe into a host pipe making it a highly flexible and effective tool in pipe replacement operations. It is also safer, avoiding the need for operatives to work in the trench.
The Pipe Handler is attached to the quick hitch or bucket pins of the excavator. The operator is then able, from the safety of the cab, to grip the PE, position it in the excavation and insert the pipe in one straightforward, efficient operation.
A joint venture with National Grid Gas, the Pipe Handler has undergone extensive field trials across the network, and following successful results a total of 8 units have been allocated across the alliances and coalitions.
LMI job in Sheffield
In Sheffield a new 315mm PE pipe was inserted into an existing 18”/20” low pressure cast iron main, using the Pipe Handler to push 1000 metres on each side of the road at record pace. The existing 20” main had a unique characteristic on one side of the street – the main branched off into a fork of three 12” cast iron mains. This unusual arrangement was due to the gas main lying above a river where the 20” pipe would have caused a loss of depth in the road surface on the bridge arch. Two of the three 12” main pipes were abandoned once the 315mm PE had been inserted and connected to the remainder 12” pipe.
With over 100 businesses being supplied by the gas main it was crucial for the replacement operation to be carried out with minimal disruption in gas supply, as well as maintaining access into establishments. Only a single excavation was required for the Pipe Handler to insert the 315mm pipe. The major safety benefit of Live Mains Insertion is that fewer excavations in roads and footpaths need to be left open for long periods, minimising the hazards for road users and pedestrians.
Live Mains Insertion
Live Mains Insertion is similar to normal insertion of PE pipe into an old cast iron main with one beneficial difference: by using a special gland box, the old main is kept live throughout the insertion process and the new PE is gassed up to maintain gas supplies to customers. Once insertion is complete, the main is still kept live to supply customers via the annular space until it is operationally convenient to transfer the services to the new main.
The Lyontec Gland Box, developed by Steve Vick International, is a disposable gland unit that fits on to the end of a main which is designed to be left in place once insertion is complete. It comprises a gas tight membrane plus internal glanding rubbers which make the insertion entirely gas free. Normally, just one open excavation is required to insert the new PE. This excavation can then be backfilled and safely left for several days or even weeks. Further, small excavations are only required to transfer the services, two or three at a time, and this can be done progressively along the length of the main.
The single excavation was used to insert the new 315mm pipe in both directions of the street. Steve Vick Lyontec Gland Boxes were fitted on either side of the abandoned cast iron main in allowance for the entire process to be completed gas free.
Due to the extensive 2000 metres of PE to be inserted in Sheffield, the length of pushes were completed in stages using the Pipe Handler, the longest distance inserted without obstruction being 750 metres over a period of only 3 days.
National Grid Gas used 12 metre sticks of 315mm PE pipe permitting up to 48 metres of pre welded pipe to be inserted by the Pipe Handler before further sticks were fused together and ready to insert
Steve Bloomer, Network Officer of National Grid Gas, summarised the benefits of using the Pipe Handler “Being able to carry out the insertion without the need for operatives to enter the excavation ensured that the work could be carried out in safer and more efficient”
Steve Vick International Special Contracting Service
Once the 2000 metres of pipe had successfully been inserted, a member of the Steve Vick International Special Contracting department carried out a flow stopping operation.
The FOAMBAGTM technique has become a gas industry standard method of flow stopping sections of gas mains to be abandoned. The technique involves inserting a semi-porous bag into the main which is then injected with an expanding PU resin foam. The bag holds the foam in place while it expands; at full expansion some of the foam seeps through the semi-porous material adhering to the pipe wall blocking the entry of gas.
A circumferential cut on the 20” cast iron main was made before the End SealTM could be fitted to give a permanent seal.
The project started in April 2009; the main was inserted over a period of 2 weeks, leaving the services to be connected at a later stage without the pressure of customers being off gas. National Grid Gas aim to complete the project by 2010.
Steve Vick International supplied all hardware and equipment required to carry out Live Mains Insertion in Sheffield, including the new Pipe Handler.
Date published – 9th September 2010