Articles & Case Studies


Posted: Thursday 3rd January 2013

U Mole (a division of Vp plc within Groundforce) recently provided a Hammerhead PB30 cable-based pipe bursting system to Saxilby-based drain and sewer specialist contractor Drain Wise for the replacement of a number of deteriorated pitch fibre pipes on a project for the City of Lincoln Council.

The project arose after survey work was undertaken at a block of flats known as Fordham House in Lincoln which was designed to establish the existing condition of the drainage facilities serving the building which had recently suffered subsidence problems and to determine if the drainage was a causal factor for the subsidence.

During the inspection work Drain Wise uncovered a number of deteriorated pitch fibre pipes that were in need of replacement, so engineers at the City of Lincoln Council awarded the contract to undertake this replacement work to Drain Wise.

As might be expected, the ground around the work site carried numerous existing services so the replacement work had to be carried out with great care and attention to minimise, if not eliminate, potential service strikes which could have led to loss of the service to residents in the block.


After careful examination of the site, ground conditions and the pipe that needed replacing, Drain Wise decided that whilst shorter lengths of the pipes involved could be replaced with open cut techniques, often hand digging, several sections, all over 10 m in length, would be better replaced using a trenchless option.

There were several reasons as to why this was the case. Firstly, the existing utilities and services including gas electric, water and communications cabling could be better avoided using a trenchless option. Secondly, the ground, which comprised not only soil but also old bricks, concrete and other debris, would need to be removed from site and transported to landfill as it could not be re-used once excavated. This in turn meant new backfill would need to be sourced and transported to site in significant quantity. The site traffic would of course have also increased significantly because of this which would have had a knock-on effect to the local area in terms of vehicle traffic and environmental impact to both the flat’s residents and the local community. Thirdly, to excavate trenches to depths of around 2.4 m (7 ft) through mixed ground with many existing services would have required extensive trench support and site security around the open cut sections.

All of these aspects of course would have significant cost implications to project and pointed the decision making process towards the trenchless option for the longer replacement runs.

Having investigated the options, it was decided that the longer pitch fibre pipe lengths could be best replaced using a pipe bursting option. Given the site conditions and the relatively limited access to the pipe burst sites and the pipe sizes involved (100 mm {4 in} diameter) it was decided that a cable-based, small footprint bursting technique would be applicable. The system chosen for the work was the PB30 unit provided by U Mole.

In total about 180 m of bursting work was undertaken with the PB30 unit over nine individual bursting runs. Reconnection of lateral connections to the newly installed plastic pipe, where it was found the laterals were still in use, were made using small scale open cut techniques.

What was impressive about the pipe bursting section of the project is that all nine bursts were completed in just over 7 working days, despite the significant difficulties with excavation of the start and reception pits given that they all encountered the numerous existing services. Despite this, once prepared, each burst only took approximately 45 minutes to complete including set up and removal of the PB30 unit. All of the burst runs were completed without problems.

For The City of Lincoln Council, Graham Twell said: “The local Council was very impressed with the method used as it showed that the council’s choice of contractor was a good one as the company was one that used the latest technology to prevent unnecessary disruption to tenants whilst necessary works were carried out.”

For Drain Wise, Dean Watson, contracts manager said of the Lincoln project: “Our choice to use the pipe bursting technique was indeed a wise one. Not only did it offer a more environmentally aware approach to the project but also took into consideration the potential disruption an open cut site would have had on the tenants of the property. The PB30 was an ideal tool for this project and we will definitely be using it again in the future. I would like to thank U Mole for its support throughout the project.”


The PB30 compact pipe bursting system has been specifically designed for the replacement of small diameter sewer laterals with minimum surface disruption and disturbance to the client. Producing up to 28 tons of pull back on a special compact cable the PB30 can be broken into several easily manageable components to ease transport/assembly in difficult access locations and even man-holes.

The use of the compact cable together with the compact bursting heads with integral pipe towing head enable the PB30 to burst in-line bends up to and including 45o with no problem.

Hydraulic power can be provided by an independent power pack or even from the hydraulics on a mini excavator.

Key Features of the system include:

· Reduce pit size & surface disturbance

· Compact – fits through a 750 mm doorway

· Rope rather than rods – simple threading

· Up to 30 t pull pack

· Runs off power-pack or mini digger

· Breaks down in to light sections

· Bursts around 45o bends

· Size for size or up-size bursting

· Remote operator controls

· Patented combined burst head and pipe puller

· Stud end cable reduces cable wear around bends

· Small footprint = smaller pits

· No screws or hand tools – 100% pipe Engagement

The power pack available through U Mole is the PP13 Hydraulic Power Pack with a Honda 9.7 kw (@ 3,600 rpm) engine which produces a hydraulic Pump Flow of 23 l/min @ 3,000 rpm to a maximum Hydraulic Pressure of 207bar

Also available with the systems are a range of Quick Grip Burst Heads which are used for the installation of PE and PVC pipes for bursting 100 mm (4 in) and 150 mm (6 in) diameter clay and pitch fibre pipes and installing new 110, 125 and 160 mm diameter PE and 100 mm (4 in) and 150 mm (6 in) diameter PVC pipes.


U Mole, a division of Vp plc is the direct factory UK and Ireland distributor for Earth Tool equipment offering the company’s full range of products for trenchless installation and pipeline replacement. This range includes impact moles (earth piercing tools), pipe ramming hammers, twin capstan winches, static rod pipe bursting systems and the portable cable-based, hydraulic pipe burster range.

U Mole also supplies a full and extensive range of trenchless and limited dig equipment including: Suction/vacuum excavation systems (including MTS systems alongside Vac-Tron systems) and surface coring equipment for the ‘Keyhole’ excavation of utilities and services with minimum disruption to the local area and minimum damage to the buried service. Other trenchless related equipment available includes the market leading Robbins SBU equipment, Pipe to Site coiled pipe trailer range, pipe fusion systems, Reed Tools and a complete range of accessories such as Cobra flexible rodding, towing heads, cable socks, pipe pigs, swivels, breakaway connectors etc.

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