A brief look at different control valves and their applications

 

Control Valves - Fluid Control Services

Control Valves

In the processing industries, many valve types are used for process control. This article examines several different control valve types, their functions and positioners.

The quarter-turn control ball valve’s design is commonly used to control liquids in throttling systems in which the direct control of flow rates working with pressure, temperature and liquid levels are vital. The opening and closing of control valves is usually carried out by pneumatic, electric or hydraulic actuators.

For modulating applications, where any position from completely open to completely closed, valve positioners are employed to control the desired degree of opening. Smart positioners are normally used nowadays in concurrence with refined manufacturing control systems.

In conjunction with segmented balls, the performance of globe valve’s characteristics is merged with the efficiency of rotary type ball valves. The segmented ball consists of a V-notch design with great cutting power and a self-cleaning machine. It is particularly suitable for the control media that contains fibre and small solids.

Initially designed for pulp and paper applications, innovative research and development using segmented ball valves have protracted their use to petroleum, petro-chemical, power, chemical, fibre and several other flow control applications.

Defined contouring of the V-notch offers excellent control characteristics for a wide range of flow applications. An ideal control performance is designed into the geometry of the ball for critical management of flow. A locked ball-to-shaft connection ensures that motion is not lost during critical control periods.

A splined connection between the shaft and ball ensures accurate control of low hysteresis. A streamlined flow passage provides maximum efficiency and minimises erosion inside the valve’s body.

Also, the detachable seat retainer design offers ease of access for the slim parts of the valves through their inlets by simply taking away screws on the retainer allowing for easy maintenance. Repair kits are freely available for all valve designs.

Greatly engineered trunnion bearing technology provides for excellent abrasion resistance. Jagged, self-adjusting metal seat options make these valves suited for high temperature applications. Spring-loaded seats maintain constant contact with the ball, providing enhanced sealing performance. Shearing action between the ball and seat in these valves promotes smooth, non-clogging operation, which is ideal for fibrous or slurry applications.

Optional special materials can be impregnated directly into all the wetted surfaces of the valve that can help prevent the build-up of scale often found in green liquor and other severe applications.

Lastly, many trim designs are also available for low flow coefficient (Cv) and noise applications – for instance, when the flow rate in an application is too low, requiring valves with very low Cv for throttling, that the standard trim on ¾- or 1-inch segmented ball valves cannot manage to achieve. These are engineered to provide precise throttling performance that meets the control requirements of additives and coatings in the paper industry.

Considering all that is available, the use of control valves in a variety of new applications is becoming more commonplace in the process control industry. Fluid Control Services (FCS) is a leading supplier of quality automated valves and flow components for industrial process control applications.

Fluid Control Services has provided state of the art automation to a diverse clientele ranging from small equipment manufacturers to the Gold, Diamond, Coal, Platinum & Copper Mining Groups, Petrochemical and Chemical, Power Generation, Food & Beverage Plants, Pulp & Paper, Catalytic Converter Factory Water Purification, Steel Production, Glass Manufacturing and Pharmaceutical Companies.

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