- Industry: Industrial valves
- Number of terms: 3113
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The relationship between valve travel and the flow rate through the valve. It is described by means of a curve on a graph expressed as an installed or inherent characteristic.
Industry:Industrial valves
The relationship between valve capacity and valve travel. It is usually expressed graphically in the form of a curve. Control valves have two types of characteristics inherent and installed. The inherent characteristic is derived from testing the valve with water as the fluid and a constant pressure drop across the valve. When valves are installed into a system with pumps, pipes, and fittings, the pressure dropped across the valve will vary with the travel. When the actual flow in a system is plotted against valve opening, the curve is known as the installed flow characteristic. Valves can be characterized by shaping the plugs, orifices, or cages to produce a particular curve. Valves are characterized in order to try to alter the valve gain. Valve gain is the flow change divided by the control signal change. This is done in an effort to compensate for nonlinearities in the control loop.
Industry:Industrial valves
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. There are two types of rangeability – inherent and installed. Inherent rangeability is a property of the valve alone and may be defined as the range of flow coefficients between which the gain of the valve does not deviate from a specified gain by some stated tolerance limit. Installed rangeability is the range within which the deviation from a desired installed flow characteristic does not exceed some stated tolerance limit.
Industry:Industrial valves
The proper definition for bench set is the inherent diaphragm pressure range, which is the high and low values of pressure applied to the diaphragm to produce rated valve plug travel with atmospheric pressure in the valve body. This test is often performed on a work bench in the instrument shop prior to placing the valve into service and is thus known as Bench Set.
Industry:Industrial valves
The distance the plug or stem moves in order to go from a full-closed to a full-open position. Also called stroke.
Industry:Industrial valves
The output pressure from an automatic controller that is used to operate a control valve. It is the input signal to the valve.
Industry:Industrial valves
The pressure at the supply port of a device such as a controller, positioner, or transducer. Common values of control valve supply pressures are 20 psig. For a 3-15 psig. Output and 35 psig. For a 6-30 psig. Output.
Industry:Industrial valves
The pressure used to position a pneumatic actuator. It is the pressure that is actually applied to the actuator diaphragm or piston. It can be the INSTRUMENT PRESSURE if a valve positioner is not used or is bypassed.
Industry:Industrial valves
The net force produced on the valve stem by the fluid pressure acting on the closure member and stem within the pressure retaining boundary. The closure member is at a stated opening with a stated flow condition. This is one of the forces an actuator must overcome.
Industry:Industrial valves
The high and low values of pressure applied to the diaphragm to produce rated valve plug travel with atmospheric pressure in the valve body. This is more commonly referred to as bench set.
Industry:Industrial valves
