definitive procedure for performing one or more specific operations or functions, that does not produce a test result. Compare test method. Note: Examples include procedures for conducting interlaboratory testing programs or other statistical procedures; for writing statements on sampling, or precision and accuracy; and for selection, preparation, application, inspection, necessary precautions for use, disposal, installation, maintenance, and operation of test equipment.

closeness of agreement among repeated measurements of the same characteristic by the same method under the same conditions. See accuracy; reliability; repeatability.

1. heating a food product prior to a subsequent treatment.

operating a burner blower prior to flame ignition to blow out possible leaked gas. See purge.

1. thermodynamically, the normal force exerted by a homogeneous liquid or gas, per unit of area, on the wall of the container.

2. force exerted per unit area. Note: The terms head and pressure often are used interchangeably; however, head is the height of a fluid column supported by fluid flow, while pressure is the normal force per unit area. For liquids, it is convenient to measure the head in terms of the flowing fluid. With a gas or air, however, it is customary to measure pressure on a column of liquid.

adj. varying flow rate through a flow control device in response to changes in pressure.

1. loss in pressure, as from one end of a refrigerant line to the other, from friction, static, heat, etc.

2. difference in pres-sure between two points in a flow system, usually caused by frictional resistance to fluid flow in a conduit, filter, or other flow system. Compare pressure loss.

allowing high- and low-side pressures to equalize or nearly equalize during idle periods by an unloading valve or by a vapor lock liquid control, or nearly equalizing inlet and discharge pressures on com-pressors to reduce start-ing torque load.