National Grid introduces 'keyhole surgery' repair method

National Grid has introduced 'keyhole surgery' for gas pipe repairs that can cut on-site time from up to five days with open cut methods to as little as five hours.

During a two-month field in London the average excavation size was reduced from 1m x 1.5m using traditional methods to 45cm diameter using keyhole the technique with a 90% first time success rate in locating the escape and a 50% reduction in reinstatement costs.

Keyhole repairs involve core drilling a hole up to 60cm diameter, removing the soil around the broken pipe by vacuum excavation and fixing the leak using long handled tools before immediately backfilling.

The utility giant has now acquired its own specialist trucks, one carrying a core drill the other a vacuum unit, which are used back-to-back to provide protection for the crews. Developed with U-Mole and based on 7.5t Daf trucks chassis the drill carrier is also fitted with a Hiab crane to lift the core and the vacuum unit has an airflow rate of 42m³/min and a remote controlled hydraulic boom to position the hose.

Beyond gas leaks other operations suitable for keyhole technology include socket injections, drill and tap encapsulation (up to 30cm) and inserting a camera, a joint locator or an emergency flow stop.