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LINEAR MOTION VALVESChristian Paolo AsequiaClassifications of ValvesAccording to Methods of Control:

Rotary rotates a disc or ellipse about an angular or circular shaft extending across the diameter of an orifice

LINEAR MOTION uses a closure member that moves in a straight line to start, stop or throttle a flow.

Parts of a Valve

LINEAR MOTION VALVESAlso known as multi-turn valve

Well known for its simple design and ease of maintenance

Tends to be slower in operation but have higher level of accuracy and stability in the position of the closure member

Closure members moves in a straight line (oftentimes, perpendicular to the seat)

ExamplesGlobe Valve

Gate Valve

Globe Valve Most common type of valve for regulating flow. also ideal for situations in which operation is frequent or tight shutoff is desired. The plug can be raised or lowered a specific amount to allow fluid to flow at a given rate. The disk-to-seat-ring contact is very close to forming right angles, which allows the force of closing to tightly seat the disk. At this point the plug will just move further down, and there will still be a tight seal. When the valve is closed, there is no blocked-in volume. As a result, globe valves tend to have very little or no leakage around the seat.

Gate Valves are primarily used for on/off applications and not to regulate flow. Gate valves are very common due to their simple design and ease of operation. The gate is raised by a threaded stem to allow fluid flow. operate in either the fully open or fully closed position. By turning the handle on the top, the screw turns and moves the wedge up or down. The wedge is angled so that if wear does occur, the wedge will still be guided into position. When a gate valve is fully open, there is a very small pressure drop across the valve. Conversely, when the valve is fully closed, it is pressurized and very well sealed. With the appropriate mating of a disk to seal the ring, very little or no leakage occurs across the disk when the gate valve is closed. Gate valves open and close very slowly to prevent fluid hammers and consequent damage to the piping system. underground water or sewage disposal applications. They are also commonly found in irrigation and distribution service lines.

Gate valves are suited for high pressures and temperatures, and are also used for low-pressure steam, and non-corrosive gas or oil.

5ExamplesDiaphragm Valve

Diaphragm valves are excellent for regulating flow. Turning the wheel of a diaphragm valve will change the flow of the passing fluid. When the wheel of a diaphragm valve is turned, it turns a screw that forces the diaphragm to decrease the incoming fluid flow rate. The diaphragm is the only part of the valve that is exposed to the fluid, minimizing erosion effects. The flow passing through the diaphragm is unobstructed by moving parts and free of crevices. 6