Ordliste

It is the arithmetic average of the absolute values of the profile deviations from the mean line of the roughness profile. Statistically very stable repeatable parameter good for random type surface such as grinding. Not a good measure of sealed surfaces.

The range over which a control valve can control. It is the ratio of the maximum to minimum controllable flow coefficients. This is also called Turndown although technically it is not the same thing.

A valve bore/port smaller than the line size or the valve end connection type.

See Venturi Valve.

A term usually applied to plug valves. The 'regular' port of such a valve is customarily about 40% of the line pipe area. Hence it corresponds to a venturi or reduced bore valve of like nominal pipe size. Venturi ball valves are often a logical alternative to plug valves with advantages in price torque and low maintenance.

A throttling or pressure-reducing valve which exercises automatic control over some variable (usually pressure). Not an on-off valve.

It is the ratio between the flow coefficient at a relative travel and the rated flow coefficient. It is usually expressed in percentage.

It is the ratio of the travel at a given opening to the rated travel and is usually expressed in percentage.

The probability that a device will operate correctly over a specified period or amount of usage.

The operation of a valve or other flow control devices from a point at a distance from the device being controlled. Can be accomplished by electrical pneumatic or hydraulic means.

The closeness of the band of measurements of repeated measurements of the same variable under the same operating conditions.

In hydraulic systems it is the storage tank for unpressurised fluid from which the pump draws its supply. It is also the vessel to which the return lines are connected.

A valve seat containing a soft seal such as an 0-Ring or a plastic insert to assure tight shut-off.

The time between an instruction to proceed with an action to the completion of the task.

See Hydraulic Seats.