Page 34 - igem-g-4 edition 2

IGEM/G/4 Edition 2
operator (of a gas pipeline)
Person who is to have or (once gas is conveyed) has, control over the conveyance of gas in
the pipeline.

outage
Unexpected unavailability of plant which was believed to be available.

outer lift (bottom lift)
Outside lift of a watersealed gasholder, having the greatest diameter, moving closest to the
walls of the tank.

outlet pressure
Pressure at the outlet of a component.

ovality
Difference between the maximum and the minimum diameter divided by the mean diameter at
any one cross-section of a pipe, generally expressed as a percentage.

over speed
Fault condition in which a machine does not respond correctly to the control of fuel flow,
leading to an uncontrolled excess speed.

overpressure cut-off device
Device which is designed to shut off the gas flow in the event of unacceptably high pressure
being detected within the system it protects.

overpressure protection device
Device designed to limit the maximum pressure to which the downstream system can be
subjected.

owner of a source of gas
Party that owns a pipeline, landfill site, container etc. from which gas is suspected to be
escaping.

oxygen enrichment
Technique that employs the enrichment of air supplied to a conventional air gas burner.

oxygen/gas burners
Oxygen and gas burners with no air present.

party wall
Wall between two adjoining dwellings or occupancies.

patch bolt
Special bolt which can be inserted into a hole in the metal of a low pressure gasholder to
secure an external patch.

peak 1 in “n” day demand
Daily demand level which would be exceeded only in 1 year in “n”.

peak instant demand
Highest instantaneous gas demand, normally measured at a rate per hour, which occurs over
a 60 second period.

peak instantaneous demand (PID)
Level of demand that represents the greatest possible demand given appliance mix, which
could be required to flow through the service.

peak level OP (peak level operating pressure)
Upper limit of variations in system pressure permitted under normal conditions.

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