Gas and water distribution networks across the UK are in constant need of repair, maintenance and renewal. Trenchless methods allow network companies to do this work more efficiently and cost effectively, but the pace of change is increasing.
For example, the UK water regulator, Ofwat, has set stringent targets on UK water
companies to reduce leakage by 15% in the current AMP7 period. This is a step change
in the drive to minimise water loss, and the water companies are having to think
outside the box to achieve their targets. In the gas sector, replacement of ageing steel
pipelines, prone to corrosion, is critical. The search for new innovative technologies is
ever more important, and often rightly focus on preventative methods and increasing
use of robotics to identify faults in pipelines. But when it comes to the actual job of
physically renewing the small diameter service pipe network, the trenchless world is still
dependent on what are now considered ‘traditional’ methods – primarily insertion
and moling.
Water companies and gas distribution network companies are steadily and methodically
working hard to replace the ageing metal pipes with polyethylene pipes (PE) to minimise
the risks of leakage and ensure the network performance is maintained. This includes
the miles and miles of small diameter service pipes which connect each property to the
mains gas pipeline. It is a painstaking task with supplies to around 22 million customers
in the UK.
More recently in the gas sector, there is increasing attention on the transition from
natural gas to alternative, zero or low carbon energy sources such as green hydrogen
and heat pumps. Some of these alternatives can utilise existing infrastructure, but in the
case of hydrogen for example, this will require polyethylene pipes for transport putting
additional pressure on the need to replace the existing steel pipes. The lower density
and lower energy content of the fuel also means large swathes of the network will need
further upgrade to potentially larger diameter pipes to carry the larger volumes.
For service pipes to properties, this may mean not only upgrading from steel to
polyethylene pipes but also from smaller diameter (20 to 25 mm) to larger 32 mm
diameter service pipes. The Gas Distribution Network companies – Cadent Gas,
Northern Gas Networks (NGN), SGN, and Wales & West Utilities (WWU), already utilise
trenchless technology wherever feasible and practical. Moling has been successfully
used to install smaller diameter polyethylene pipes for decades and inserting a
polyethylene pipe through the existing steel service pipe is similarly widely used to
minimise the amount of expensive and disruptive open cut excavation. But both
have their limitations. Moling carries an inherent risk of damaging surrounding
utilities or veering offline in certain ground conditions, not to mention the negative
environmental impact of leaving the decommissioned pipe in the ground. Insertion
is limited in length to ensure sufficient volume of gas can keep all the gas appliances
working.
The UK gas network now has a viable alternative trenchless technology to replace
existing small diameter (up to 32 mm) service pipes with new PE pipes. Pipe Pulling
has been used extensively in the UK water industry and in the North American gas and
water sectors to replace steel, copper, lead and PE service pipes. The development
of the technology by Kobus Services, the originator of the technique from its original
concept used by the water industry, has required extensive testing over hundreds of
trial sites across the UK.
The process is simple, robust and user friendly. The technique involves feeding a
steel pulling cable through the existing pipe and attaching the cable to a powerful
hydraulic winch (Pipe Puller). Two small excavations are required at each end of the
existing pipe so keeping disruption to homeowners, pedestrians and road users to a
minimum. The new PE pipe is towed into place behind the old pipe as it is removed in
a single operation. For the gas networks in the UK, pipe pulling offers a safe, reliable
and cost-effective technology that compliments the other trenchless techniques. Pipe
pulling is installing a new pipe through the bore hole created by the old pipe and
therefore virtually eliminates the issue of utility strikes, making the system inherently
safer for operatives and members of the public. The Kobus Pipe Puller is available in
two formats. One, KPP300, is modular and the hydraulic winch is powered by its own
separate power pack. The other, the KPP400 is mounted on a compact excavator and
is driven from the auxiliary hydraulics of the excavator. This minimises the amount
of manual handling and operators can be at a safe distance from the machine during
operation, improving overall safety. The replacement of steel gas service pipes will
benefit from this technology in a variety of ways: (a) less disruption to homeowners,
local residents and traffic, (b) reduced risk of utility strikes, (c) ability of replace pipes <
1 in (25 mm) diameter trenchlessly, (d) replace steel pipes with larger diameter PE up
to 32 mm, (e) offering up to 80% cost reduction and less time consuming than open
cut method.
