two flanges in a pipeline, used to create a drop in pressure
which is proportional to flow and can be used to measure the
flow or to modulate control devices.
Occupational Safety and Health Act of 1970.
Pacific Air Force.
Pantograph. A series of pipes, joined by flexible joints,
used to connect fueling equipment to aircraft.
Parallel Pumps. Two or more pumps having common suction and
Particulate Matter. Solid particles such as dirt, grit, and
rust, which contaminate fuel.
Pressure dew point.
pH. A number assigned to indicate whether a substance is
acidic or alkaline (pH 7 is considered neutral, less than 7 is
acidic and more than 7 is alkaline).
Pigging. The use of cleaning devices, called pigs or go-
devils, to clean out the inside of pipelines.
Pig Trap. An arrangement of valves and closure devices to
trap cleaning pigs at the end of their run through a pipeline.
Pile Cluster. A group of pilings driven close together and
usually wrapped with wire rope to act as fender or mooring for
Programmable logic controller.
POL. A commonly used abbreviation which broadly refers to all
Pour Point. The lowest temperature at which an oil will pour
or flow without disturbance.
Pontoon Roof. A type of floating roof for a storage tank
having liquid-tight compartments for positive buoyancy.