Usually, non-mechanical, Flow Control valves typically rely on the conditions of the regulated substance to close or open the device. Monitoring devices such as temperature gauges and pressure gauges are sometimes used to regulate Flow Control valves.
Gate valves are general service valves that are mainly used for on/off, non-throttling service. The valves are commonly used in applications that require a straight-line flow of liquid where a minimum restriction is needed. Gate flow control valves operate when you rotate the stem in a clockwise to close (CTC) motion or a clockwise to open (CTO) motion. The gate moves up or down on the threaded step when a user moves the stem. This is why it is a multi-turn valve; the valve must turn several times for it to go from open to closed. The slow operation prevents water hammer effects. The two types of gate valves are parallel and wedge-shaped. The parallel gate valve features a flat gate between two parallel seats. While the wedge-shaped gate valves are made of two inclined seats and an inclined gate that is slightly mismatched.
Diaphragm valves are identified by a flexible disc that contacts a seat at the top of the valve body and forms a seal. The diaphragm is flexible and pressure-responsive. It also communicates force to open, close, or control a valve. The diaphragm valves are related to pinch valves since they both use an elastomeric diaphragm rather than an elastomeric liner in the valve body. The elastomeric diaphragm is connected to a compressor and splits the flow of the stream from the closure element. Diaphragm valves are perfect for managing corrosive, erosive, and dirty services.
The most cost-effective of the flow control valves are pinch valves. These valves are perfect for applications of slurries or liquids containing decent amounts of suspended solids. Pinch valves stop the flow from using one or more flexible elements like rubber tubes that become pinched to turn off the flow of liquid from running through. These rubber sleeves are the valve’s only wetted part. Air or hydraulic pressure is placed directly on the elastomer sleeve to actuate pinch valves. Their maximum flexibility permits for pinch valves to close firmly around trapped solids.
Needle valves are volume control valves that limit liquid flow in smaller lines. The liquid moving through the valve turns at a 90-degree angle and flows through an orifice that works as the seat for a cone-shape-tipped rod. The orifice size will change when the operator moves the cone in relation to the seat.
Globe valves are a linear motion valve that is used to stop, start, and regulate the flow of liquid. These valves create a closure by using a plug with a flat or convex bottom that is lowered onto a horizontal seat found in the center of the valve. When opening the globe valve, the plug will rise to allow the liquid to flow. These valves are used for on/off and throttling applications. The disk of the valve can be detached from the flow path completely or it can fully close the flow path.
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