Email:alina@tkfm.cn Shenyang Taike Fluid Control Co.,Ltd

Shenyang Taike Fluid Control Co.,Ltd

Various Control Valve Functions And Terminology

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Spring setting range: Regulating valve (control valve) Actuator spring adjustment range to balance the actual process force.

Circulation capacity: the rated flow through the valve under the specified conditions.

Clearance flow: The flow below the minimum controllable flow rate when the shut-off element is not seated.

Diaphragm pressure range: diaphragm pressure range of high and low value of the difference. This can be considered as an inherent or installation feature.

Double-acting actuator: An actuator that can be powered in either direction.

Dynamic unbalance force: As the process of fluid pressure, at any prescribed opening, the net force generated in the spool.

Effective area: In the film actuator, the effective area is the area of the diaphragm that effectively produces the output force. The effective area of the diaphragm may change as it moves, usually at the beginning of the stroke and at the end of the stroke. Molded diaphragms have a smaller effective area change than flat diaphragms, so molded diaphragms are recommended.

Equal Percentage Flow Characteristics: (See "Process Control Terminology": "Equal Percent Flow Characteristics.")

Loss of gas - Off: A condition where the valve shutoff element is moved to the closed position when the drive energy is lost.

Loss of gas - Open: a state where the valve shutoff element is moved to the open position when the drive energy is lost.

Loss of gas - safety: a valve and its implementing agencies

Features: When the drive energy supply is interrupted, the valve shut-off element is moved fully closed, fully open, or left in the last position. Either position is considered necessary to protect the process. Fail-safe mode of operation may require the use of auxiliary controls connected to the actuator.

Flow characteristics: The relationship between the flow through the valve and the percentage of the rated stroke when the percentage of rated travel changes from 0 to 100%. This term should always be expressed as an inherent flow characteristic or an installation flow characteristic.

Flow Coefficient (CV): A constant (CV value) associated with the geometry of the valve that is used to measure flow capacity for a given stroke. It is the U.S. gallon of 60 ° F water flowing through the valve per minute at a pressure drop of 1 pound per square inch.

High Pressure Recovery Valve: A valve construction that disperses relatively little fluid energy due to the streamlined internal profile and minimal fluid turbulence. As a result, the pressure downstream of the valve's retracted section returns to a very high percentage of the inlet pressure. Direct-flow valves, such as rotary ball valves, are typical high pressure recovery valves.

Inherent Die Pressure Range: High and low pressure acting on the diaphragm to create a nominal spool stroke at atmospheric pressure. This range usually refers to the spring setpoint range, because when the valve is set in the working range, this range will be the valve range of motion.

Inherent flow characteristics: The relationship between the flow and the closure element stroke as the valve moves from the closed position to the rated stroke as the pressure drop across the valve is constant. Installation Diaphragm Pressure Range: High and low pressure applied to the diaphragm to produce a nominal spool stroke under the valve body's specified operating conditions. Due to the forces acting on the shut-off element, the inherent diaphragm pressure range may differ from the diaphragm pressure range.

Installation Flow Characteristics: The relationship between flow and shut-off element as the pressure drop across the valve is affected by changing process conditions as the valve moves from the closed position to the rated stroke.

Leakage: (See "Seat Leakage.") Linear Flow Characteristics: (See "Process Control Terminology": "Linear Characteristics.")

Low pressure recovery valve: A valve structure that disperses a large portion of the fluid energy due to turbulence created by the fluid channel profile. As a result, the pressure downstream of the systolic section of the valve returns to a lower inlet pressure percentage than the valve with more streamlined passages. Although each valve structure is not the same, ordinary straight-through valves often have low pressure recovery capabilities.

Modified parabolic flow characteristics: A flow characteristic that provides equal percentage characteristics at the lower stroke of the shutoff element and linearity at the upper stroke of the shutoff element.

Often shut the valve: (see "loss of gas - off.")

Often open the valve: ("see lost - open".)

Pushed down to close the structure: A through-type valve structure, the closure element is located between the actuator and the seat ring, so push rod actuator will move the closure element to the seat ring, and finally close the valve. The term can also be used for rotary valve construction. In rotary valve construction, the linear extension of the actuator stem moves the ball or disc toward the closed position. (Also known as positive.)

Push down to open the structure: a straight-through valve structure. Its seat ring is located between the actuator and the shut-off element so that the push of the actuator releases the shut-off element from the valve seat, thus opening the valve. The term can also be used for rotary valve construction. In rotary valve construction, the linear extension of the actuator stem moves the ball or valve plate to the open position. (Also known as reaction).

Fast-opening flow characteristics: (see "Process Control Terminology": "Quick-Opening Characteristics.")

Adjustable ratio: The ratio between the maximum flow coefficient (CV value) and the minimum flow coefficient (CV value) when the deviation from the specified flow characteristics does not exceed the specified limits. When the flow rate increases to 100 times the minimum controllable flow rate, a valve that is still well controlled has a 100: 1 adjustable ratio. Adjustable ratio can also be expressed as the ratio between the maximum and minimum controllable flow.

Rated flow coefficient (CV value): rated flow valve flow coefficient (CV value).

Rated stroke: the valve closing element moves from the closed position to the rated full open position. Rated full open position is the maximum opening recommended by the manufacturer.

Relative flow coefficient: The ratio between the flow coefficient (CV value) at the specified stroke and the flow coefficient (CV value) at the rated stroke.

Seat Leakage: The amount of fluid flowing through the valve when the valve is fully closed at the specified pressure differential and temperature.

Spring Coefficient: The change in spring force per unit change in spring length. In diaphragm actuators (control valves), the spring constant is usually expressed in pounds per inch of compression.

Stem Unbalanced Force: The net force generated on the stem at any position due to fluid pressure.

Reduced flow section: the part with the largest flow velocity, the lowest hydrostatic pressure, and the smallest cross-sectional area. In a control valve (control valve), the contraction section is usually located downstream of the actual physical limit.

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