Propump Engineering Ltd has encapsulated 900 linear metres of pipework at the new £500 million combined heat and power (CHP) station on the Isle of the Grain, Kent. One of the world’s largest CHP power stations, some 2,500m3 of foamed concrete was used to fill underground shafts and protect pipes used to transport hot water from the power station to the nearby liquefied natural gas (LNG) terminal.
The 1,275MW gas-fired power station has three combined-cycle units that burn natural gas and supply waste heat of up to 340MW, in the form of hot water. The water is transported to the LNG terminal in two 1200mm diameter glass-reinforced plastic (GRP) pipes that were installed into twin 2200 mm diameter tunnels, running beneath roads and cryogenic crossings.
To provide a cost-effective, annulus fill solution to secure and protect the extensive underground pipework, Civil Engineering Contractor Clancy Docwra Ltd called on Propump Engineering Ltd. With a proven track record in providing quality service and accurate volumes of foamed concrete, Propump was appointed to complete the job to the highest standard possible.
Lightweight and self compacting, 800kg/m3 density foamed concrete was the perfect solution to encapsulate the pipework and fill the receiving shafts, with some of these shafts nearly 22 metres in depth. Proving more economical than traditional fill materials, the foamed concrete was produced on the 10 acre site, and then pumped into the various locations, with pours of up to 290m3 completed in a standard working day.
Requiring special attention to detail, the cryogenic tunnels rose at a steady incline over its length of 100 metres, from a 22 metre depth at one end to only 6 metres below ground level, at the other. To overcome the issues of infilling this profile, Propump designed a pour sequencing programme that utilised a series of sacrificial pump lines, allowing the twin pipes to be filled in stages of 1 metre lifts. Upon completion of the bore infill, the reception shafts were also infilled to just below ground level.« Foamed concrete fills the voids at Southern Water’s highest CCS rated scheme