The pipe replacement work beneath Easterly Road, Leeds was undertaken by David Carr for main contactor Enterprise which had been engaged by client United Utilities project manager for Northern Gas Networks.
The pipe replacement project formed part of a larger scheme to replace the existing main gas pipeline, the work for which was originally all scheduled to be completed in open cut. However, the section beneath which pipe replacement was employed ran under the main A58 dual carriageway, a main artery route to and from Leeds. This meant that without using costly nightshift working and major traffic disruptions across an eight-way intersection with Weatherby Road, open cut was not a practical option.
This was when David Carr decided to look at pipe bursting the existing gas main and replacing it with size-for-size (400 mm diameter) PE pipe. Close examination of this part of the project showed that pipe bursting the 300 m long section could be completed with minimum disruption to traffic flows, more easily and quickly and at about 50% of the cost of the open cut option. The trenchless replacement option also meant that night shift working could be avoided, so eliminating any potential overnight disturbance to nearby local residents etc.
The pipe replacement works called for the 300 m length to be undertaken in three separate 100 m long sections. The ground through which the pipe burst needed to run was difficult to investigate due to the majority of it being beneath the busy road way. Start and reception pits were established off the roadside in ground conditions which indicated that good clay ground should prevail across all three sites.
Machine Choice
The choice of machine to use for the work was more or less dictated by the size of the pipe being replaced and the new pipe being installed, which at 400 mm diameter was substantial. After investigating machine availability in the hire market, Carr found that one of the few systems for hire with the power and pullback required for this level of pipe burst was the Hammerhead HydroBurst HB100 available through U Mole.
The latest Hammerhead™ Hydroburst HB100 pipe bursting system offers a design with a smaller (10% less) overall machine footprint than it predecessors for reduced pit sizes whilst offering around 25% more pulling force, which made it just the choice for the 400 mm diameter replacement in Leeds. The smaller footprint does however mean that it can also be utilised to replace pipe of as little as 75 mm diameter should the situation demand it, making it a very versatile unit.
The unit’s controls have been redesigned to set a new standard for ease of operation in higher tonnage static pipe bursting machines with only two levers required to control all pipe bursting functions. The machine also offers simple one man operation, with an on board rod basket, and just 16 second rod payout per 1 m rod.
In average soil conditions, a 120 m pull takes as little as two hours to complete including rod payout and pullback. Features like the ‘rod lock vise’ prevent production loss from rod rebound and 45 m of onboard rod storage reduces the onsite footprint of equipment and increases efficiency.
The HB100 also features a lightweight heat treated alloy rod with an API style joint. This proven design handles thrust loads encountered when pushing around sweeping bends, through encrusted and collapsed lines and long burst lengths. When coupled with the line of HammerHead Ductile Slitters, the HB100 bursts even the toughest host pipes including ductile iron and steel.
Optional equipment includes a rod spinner that quickly makes/breaks rod joints, increasing overall production. As conditions change during a burst, optional hydraulic leveling jacks can be adjusted to keep the machine on grade and aligned with the existing utility without having to stop the burst and re-shore or level the machine.
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