Pneumatic and electric globe control valves

In the process sector we look in detail at the specific application in terms of sizing, selection and materials of construction for the end user to ensure the technical specification is met and the correct product is specified.

Electric and pneumatic linear control valves Self acting regulating valves with high limit Pressure regulating control valves High performance butterfly valves including double and triple offset Rotary valves including V notch and segmented ball valves Electric and pneumatic valve actuator packages

Control Valves in general regulate the flow of fluids in flow, pressure, level, and temperature control systems. They generally consist of three main parts: the control valve body, pneumatic or electric actuator, and a valve positioner. The positioner, through the actuator, drives the valve in proportion to a control signal such as a 4 – 20 mA control signal. There are numerous control valve types on the market, with various types of valve and actuator combinations to suit most process control applications, We give a brief overview below, but please contact Valveforce Ltd for full sizing, specifying and selection.

Linear globe control valves are the most rugged and reliable throughout the size range, Valveforce supplied DN 15 up to DN 300 in linear control style, The up and over globe control valve style, provides excellent energy conversion of the process fluid resulting in accurate, repeatable control. A full range of control valve actuators are available as well as control valve positioners to complete the package.

Rotary control valves consist of cammed plug and segmented "V" ball designs. They have similar control characteristics to reciprocating globe valves with the benefit of low friction from rotary motion. Rotary valves inherently have significantly more capacity and turndown (rangeability) than reciprocating globe valves. Their low cost and comparable installed accuracy performance make rotary globe valves preferred in general service applications.

Vee-Port Ball control valves consist of a Vee Ported ball design and are available with 30, 60, and 90 degree characteristics. V-Port Ball Valves are ideal in sizes up to 4" for general flow control applications where economy, simplicity, and the sealing features of a quarter-turn ball valve are of value. Pre packaged systems are available complete with pneumatic and electric modulating actuators and positioners.

High-Performance Butterfly Valves (HPBV) consist of Double and Triple Offset Discs which provide a modified parabolic characteristic. HPBV's are ideal in sizes greater than 3" for general flow control applications where economy, simplicity, and the sealing features of a quarter-turn butterfly valve are of value. Pre packaged systems are available complete with pneumatic and electric modulating actuators and positioners.

Pressure regulating control valves provide constantly controlled liquid, gas, and steam pressures in process piping systems. They are typically used to reduce inlet supply pressures to an efficient operating pressure and can also be used to maintain constant back pressures. Select regulator size based on flow requirement and operating pressure range. Typically, the lightest spring range will provide the best performance. However, a heavier spring can help dampen unstable systems.

Actuator Selection: Actuators are used to operate valves automatically and/or remotely. Actuators typically use pneumatic, electric and hydraulic power to actuate a valve shaft. The force output of the actuator must be sufficient to overcome valve static friction and dynamic torque. Static friction is developed in the metal-to-metal surfaces, seats, and seals. Dynamic torque is the unbalanced force of the process acting on the plug, disc, or ball. Valve torque requirements are supplied by the manufacturer and based on pressure drop across the valve.

The on/off actuator positions the valve in the open or closed position. Modulating actuators use controllers/positioners to maintain a valve position based on an input signal.

Full control valve packages are specified and supplied by Valveforce Ltd

Pneumatic double acting actuators use gas, typically air or nitrogen to pressurize a double acting cylinder. An unbalance in the opposing cylinder areas drive the connected shaft in the required direction. A 4-way solenoid valve is used to switch pressure between the cylinders.

Pneumatic spring return actuators are generally spring opposed pneumatic cylinders. A 3-way solenoid valve is used to operate a spring return actuator. The normal position is the position of the valve with the spring extended and the solenoid de-energized.

Electric valve actuators use a reversing electric motor and gear reduction to drive a valve shaft. A given motor size and gearbox are matched to provide the most effective force output. The output force is measured in inch or foot pounds of torque. Standard voltages are 220-480VAC/3-phase, although single phase and 110VAC and 24 V options are available. Torque switches are used to position the valve open and closed. The normal position is the position of the valve with the solenoid de-energized. Electric actuators inherently fail in the last position. Battery back up is needed to drive the actuator to a specific fail safe position.
A full range of isolating valve are available from Valveforce Ltd, contact us to discuss how we can be of help with your gate valve, globe valve, and check valve enquiries.