Underpressure connections involve the fixing of a full bore valve onto the pipeline to be drilled via a clamp or underpressure tee.

The assembly, once fitted to the pipeline, is pressure tested to ensure a good seal onto the pipewall. The underpressure drilling equipment is fixed to the outside face of the valve and the cutter is positioned through the valve and onto the pipewall before commencing the cut.

When the cut has been completed the cutter, containing the removed pipewall section, is withdrawn back through the valve which is then closed. The machine is then depressurised and removed. This allows a connection to be made to the new valve, and when it is opened makes the lateral connection 'live'.

Underpressure drilling operations can be undertaken with a selection of our specialist equipment, on all diameters and types of pipeline material. We have recently developed a range of underpressure drilling machines to make clean and technically acceptable cuts into GRP (Glass Reinforced Plastic) pressurised pipelines.

We also supply a range of standard and special underpressure fittings which can be used on pipelines for probe entry points, pressure indicators and temperature sensors. These special fabricated fittings can be made to suit external diameters to allow lateral connections to be made up to size off size.

The underpressure connections can be made into water, gas, oil, or process pipelines. Special high temperate fittings and seals are also available.