CWPH Drilling Works

CWPH Formation of Pump Chamber

Woodenbale 2000 was awarded the works after successful tender to open an existing chamber at the CWPH (cooling water pump house) on the Pembroke Power Station for RWE. The existing chamber is situated adjacent to 10no: existing pumps currently pumping sea water around the system to cool the turbines at the power station. This chamber will be used to house the spare pump which stands approx. 5m high from the ground and drops below into the chamber approx. 10m.

The existing chamber was covered by pre-cast concrete lids with a 500mm+ concrete slab cast over the top which was heavily reinforced. Woodenbale Engineer took detailed surveys of the spare pump and existing insitu pumps to determine the exact setting out of 2no: service entry points (1 at 150mm and 1 at 350mm diameter), 12no: 42mm holding down bolts set out in 4 groups of 3, 16no: 20mm rebar stitch anchors which were designed to hold the pre-cast units to the concrete slab following the removal of the 1650mm section. A 1650mm opening was to be formed by stich drilling through the slab as there were no entry points to within the chamber. This section of concrete which would weigh in excess of 3.5tonnes would be retained by 3no: lifting eyes which were also resin anchored into position.

Pull tests were carried out to ensure the suitability of the specified 20mm diameter resin anchored lifting eyes with a single point holding the force of a little over 4.4tonne with no failure of the resin anchor, each anchor would only be required to support a load of approx. 1.2tonne during the lift. More force could have been applied but the test was to prove suitablity of the spec not to test the failure point of the lifting eye.

Following the test the 16no: stitch anchors and additional lifting eyes were resined into position and allowed to cure.

The 1650mm section of concrete was hooked up to the over head gantry crane during the stitch drilling and was lifted out whole following successful completion of the drilling by 'D-Drill Master Drillers'.

Following the removal of the concrete section the exposed reinforcement was treated with a sealant and primer with the concrete face being rendered with a specialist repair mortar. 12no: Duplex Stainless Steel holding down bolts were then supplied and installed using the Hilti Hit resin system. To this 4 no: steel plinths were fabricated to design spec and placed over the holding down bolts and grouted into place. The new spare pump holding chamber was then inspected and handed over to the client.

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ID: 21  Revised:05/05/2017 15:24:14