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Services subcontractor Thompson
Utilities. This was designed by adapting
a dome head using a specialised mesh
gauze positioned inside the head to stop
rust, common in larger pipes, entering
the PE pipe.
Following air pressure testing, a
calculated number of holes were drilled
into the dome head to allow gas from
the network to flow into the 250mm PE
pipe. Concise calculations were then
made on the flow of the gas to ensure
there was enough gas in the annular
space to provide an uninterrupted
supply to Wickwar residents
throughout the insertion process.
Following successful trials, the
suggestion to use the LMI technique
for PE above 180mm, which comes
in lengths rather than coils, was
proposed to the Wales & West Utilities
innovation committee.
Project Leader at Wales & West
Utilities Paul Breakey then discussed
the feasibility with Steve Vick
International and it was agreed in
principle that LMI could be carried
out on larger pipes. After a number of
successful trials, and completion of
the G23 documentation and deviation
paperwork, Wales & West Utilities
approved the system in late 2018.

The LMI technique provides
a safe, fast and efficient
method of replacing old cast
iron mains with new PE
pipe, without interruption to
customer gas supplies

Live mains insertion
To all intents and purposes, live mains
insertion (LMI) mirrors the normal
insertion of PE into an old cast iron
main, with one important difference;
by using a special gland box and a live
head on the PE, the old main is kept live
ales & West Utilities (WWU) developed by Steve Vick International throughout the insertion process and
and long-term contracting (SVI), on larger diameter PE pipe. the new PE is ‘gassed up’ to maintain
partner Morrison Utility Using the live LMI process enabled supply to customers.
Services (MUS) have the replacement of approximately Once insertion is complete, the main
W completed a global first by 4,200m of ageing 12in cast iron pipe is kept live to supply customers with
using the ‘live’ live mains insertion with 250mm polyethylene (PE) pipe, gas via the annular space until it is
(LMI) process during gas mains including a record-breaking insertion operationally appropriate to transfer
replacement works in the village of for large diameter PE pipe of 1,014m, services to the new PE main.
Wickwar, Gloucestershire. without any interruption to gas supplies A further benefit of live mains
The LMI technique provides a safe, fast for WWU customers. insertion is that only one open
and efficient method of replacing old cast The Wickwar project involved pushing excavation is required throughout
iron mains with new PE pipe, without a 250mm PE pipe inside a 12in CI main, the insertion process, reducing traffic
interruption to customer gas supplies. leaving an annulus of 200mm. The PE management requirements – a major
However, the project in Wickwar broke pipe had a ‘live head’ attached, designed consideration with the cost implications
new ground by using the live LMI process, and manufactured by Morrison Utility of the new Traffic Management Act.

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