The Background

When a landslip caused a water main on the Brecon Beacons to split in two, engineering contractor O’Connor Utilities called upon Selwood’s pump rental specialists for support.

The team was asked to survey, supply and install a suitable temporary pump station while testing, swabbing and  commissioning to the main took place. The existing pipework also needed to be swabbed and re-chlorinated so that it could be safely be brought back into service for drinking water use.

The Challenge

The broken main’s position was in an area of natural beauty with limited access and space to work in. Achieving the required pressure to carry out the operation was a major challenge.The full run of pipework was almost 3km long and 600mm in diameter. Only 15 litres per second could be drawn from the gravity-led supply line, meaning the supply pressure to the pumps was extremely low at between 0.2 and 0.4 bar.

By contrast, at least 3 bars of pressure would be needed to push the swab through the main - and because it needed to go 95 metres uphill, the total head required would be near 12.5-13 bar. The solution needed to boost the pressure – but carefully, because the existing buried pipework was only rated to 16 bar and needed to be protected. Because drinking water was involved, only equipment approved under the WRAS (Water Regulations Advisory Scheme) could be used.

The Solution

The Selwood team’s solution was a 55kw electric-driven Lowara clean water WRAS approved pumps, which is capable of producing 12.5 bar of pressure with ease. The pump was coupled to a Power Electric towable 100kva Generator, towable fuel bowser and 55kw Variable speed drives, giving total control of pressure and flows. Once the pumping began , the system was running 12 hours a day and shut down overnight.

To ensure pressure didn’t exceed the pipework’s rating, a mechanical gauge was inserted into the pump inlet to monitor pressure, and a digital gauge on the outlet had switching capabilities which would automatically shut the pump down if pressure went over 16 bar. A Selwood electrician was on site each day to monitor the pump and make changes as and when they were needed. This meant that if anything went wrong, a team member was on site to fix problems and make changes immediately.

The electrician also monitored the pump and recorded pressures every 15 minutes, as well as keeping an eye on the temperature of the pump. To ensure continuity in the event of a breakdown, duplicates of all equipment used, including the generator, bowser and pump, were stored in the O’Connor Utilities laydown area just in case anything failed and needed to be swapped out at short notice.

The Result

Selwood’s solution ensured the water was successfully over pumped for the duration of the repair, and the job was completed without incident and on schedule.