Push-in Installation Method

THE ALTERNATIVE TO DRILLING

The heat exchanger installation consists of a series of 60mm diameter; 1m-length heavy-duty steel casings which are pushed into the ground using hydraulic rams mounted within a 31 tonne CPT unit (UK17). The casing is capped with a disposable tip to prevent it becoming plugged with soil as it is advanced.

HDPE pipe

Once at depth ( between 20 and 40m), a 40mm flexible HDPE pipe with an end cap is installed through the casing and connected to the disposable tip at the base of the casing.

The pipe is then filled with a heat transfer fluid (water) to make it rigid. The tip is de-latched and the casing pulled back very slowly over the first 2-3m, whilst maintaining downward pressure on the pipe to ensure tip depth is maintained. After this, the lateral stresses within the soil secure the installation tip and depth.

Optimal thermal contact

As the casing is rapidly withdrawn, the soil squeezes back around the HDPE pipe and so leaves it in direct contact with the soil over the depth of the installation.

This ensures that the installation has optimal thermal contact with the ground.

Backfilling with high conductivity bentonite grout is not required in order to ensure that an effective long-term thermal contact with the ground is achieved.

                          Flexible HDPE pipe connected into the
                          disposable tip at the base of the casing


Flow and return system

Once the casing is withdrawn, a continuous length of 25mm HDPE pipe is installed through the 40mm pipe to provide the co-axial or flow and return arrangement. The installation is then connected by a manifold at the 'headworks to provide the flow and return system.

The heat transfer fluid runs down through the 25mm pipe annulus and back up the 40mm pipe annulus to the heat pump.

The pipe is connected to a network of HDPEs laid within near-surface trenches, they are subsequently backfilled and the surface levelled. The near-surface network is then joined to the central heat exchanger manifold connection to the pump, and pressure tested and signed off by the Client, ready for commissioning.


Production

Up to 250 linear metres of installation can be achieved in a single working day using Lankelma Green Energy's 23 tonne CPT system.