7/30/2019 Valves Description

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Type Description Advantagee valves Linear motion valves used to start and stop flow. The valve is

completely opened when the disk is removed from the flowstream. Classification of gate valves is made by the type ofdisk used: solid wedge, flexible wedge, split wedge, orparallel disk.

Image Credit: Cameron

No resistance to flow when openLittle pressure dropGood sealing when closedLittle/no leakage

be valves Linear motion valves used to start, stop and regulate flow.The disk moves perpendicular to the seat to open or close theflow so the annular space between the disk and seat ringgradually changes. There are three body designs for globevalves: Z-body, Y-body, and angle and three designs for thedisk: ball disk, composition disk, and plug disk.Image Credit: Flowserve

Throttling and regulating flowLess seat leakage than Gate Valve

valves Rotational motion valves used to start, stop or throttle flow. Ituses a ball shaped disk with a hole in it. When the valve isopened the hole of disk is turned in-line with the direction of theflow. When the valve is shut, the ball is rotated so that the holeis perpendicular to flow direction.Image Credit: Cameron

Less expensiveLow maintenance costsLow torqueQuick action on/offCompactNo lubricationTight sealing

g valves Rotation motion valves used to stop and start fluid flow. Thedisk is a solid tapered or cylindrical plug with a bored passage atthe right angle to the longitudinal axis of the plug. When open,the plug lines up with the inlet and outlet port of the valve body.The plugs are either round or cylindrical with a taper. Plugvalves are easy to adaptImage Credit: Cameron

Rotational motionSuitable for multi-port designs

phragm valves Linear motion vales that are used to start, regulate, and stopfluid flow. The disk is flexible and seals with the seat in an openarea at the top of the valve body.

Image Credit: Dharmi engineers

Well-suited for difficult environments (corrchemicals, slurries, radioactive fluids)

Ability to throttle

ucing Valves Automatic valves that reduce supply pressure to a preselectedpressure. The supply pressure must remain at least as high asthe selected pressure.

Automatically reduces supply pressure topreselected pressure

ch valves The simplest of any valve design. Pinch valves consist of a Relatively inexpensive

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http://www.globalspec.com/learnmore/flow_control_flow_transfer/valves/industrial_valves

sleeve molded of rubber or other synthetic material and apinching mechanism. The pinching mechanism, a bar or gate, islowered onto the valve body to cut off the flow through thesystem.Image Credit: Flowrox

On/off as well as throttling/regulatingGood for slurries, solidsWell-suited for difficult environments

terfly valve Rotary motion valves that can be used in on-off and throttlingsystems. They are quick and easy to operate. The flow controlelement is on either a vertical or horizontal axis and is openedwhen the handle is rotated 90 degrees and closed when thevalve is turned an additional 90 degrees.

Image Credit: Cameron

On/off as well as throttle/regulateEasily/quickly operatedGood for large flow/low pressure applicatioto saving in weight/size/costGood for slurries/suspended solids.

dle valves Needle valves have a long, tapered, needle-like point that isused to make relatively fine adjustments in the amount of fluidflow. They are sometimes used as component parts for other

valves because the needle allows for a gradual change in thesize of the fluid flow opening.

Good for fine adjustment throttling

ck valves

e Credit: Cameron

Check valves are used in systems employing gate valvesbecause they prevent the reversal of flow in the piping systemand there is a low pressure drop across the valve. The pressureof the fluid through the system opens the system, while theweight of the check mechanism will close the valve if the flow isreversed.

Prevents reverse flow

ef and safetyves A relief valve opens slowly as the pressure increases about theset-point and only opens as necessary. A safety valve rapidly

opens as the pressure setting is reached and will stay open untilthe pressure is lower than the actuating pressure set-point. Bothvalves are used to prevent damage by relieving accidental over-pressurized fluid systems.Image Credit: Watts

Prevents over-pressurizationRelief valves are used for incompressible flsuch as water or oil

Safety valves are used for compressible flusuch as steam.

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