Industry glossary
Terms you will meet in the documents, systems and scenarios.
Permit to work
A written authorisation that defines the scope, isolation, controls and restoration steps for work on a live gas asset.
Squeeze-off
A tool that flattens a polyethylene pipe to stop gas flow temporarily during repair or connection work.
Lower explosive limit (LEL)
The lowest concentration of gas in air that will ignite, used as the scale for portable detector readings.
District regulator
A station that reduces and controls pressure from a higher pressure main into a lower pressure distribution network.
City gate
The facility where gas enters the distribution network from the transmission pipeline, with metering, heating, regulation and odourisation.
Cathodic protection
An electrical method of preventing corrosion on buried steel pipe by making the pipe the cathode of a controlled circuit.
Odourisation
The addition of a strong smelling compound to natural gas so that escapes can be detected by smell.
Purge
The displacement of air with gas, or gas with air, from a pipeline section so that no explosive mixture remains inside it.
Unaccounted for gas
The difference between gas entering the network and gas measured at customer meters, including leakage, venting and metering error.
As laid drawing
A drawing prepared after construction that records the exact position, depth, size and material of a main or service.