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Introduction to Control Valves
Introduction to Control Valves |
What is a Control Valve?
Modern processing plants utilize a vast network of control loops to produce an end product for market. These control loops are designed to keep a process variable (i.e. pressure, flow, level, temperature, etc.) within a required operating range to ensure a quality end product is produced. Each of these loops receives and internally creates disturbances that detrimentally affect the process variable (PV). Interaction from other loops in the network also provide disturbances that influence the process variable.
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Sliding-Stem Control Valve Terminology
Actuator Stem Force:
The net force from an actuator that is available for actual positioning of the valve plug, referred to as valve travel.
Angle Valve:
A valve design in which the inlet and outlet ports are perpendicular to each other. See also Globe Valve.
Actuator Spring:
A spring, or group of springs, enclosed in the yoke or actuator casing or piston cylinder that moves the actuator stem in a direction opposite to that created by loading pressure.
Actuator Stem:
The part that connects the actuator to the valve stem and transmits motion (force) from the actuator to the valve.
Actuator Stem Extension:
An extension of the piston actuator stem to provide a means of transmitting piston motion to the valve positioner.
Bellows Seal Bonnet:
A bonnet that uses a bellows for sealing against leakage around the closure member stem.
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Introduction to Control Valves
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