Valve 

A valve is a device which is use to regulate / control the flow of a fluid (fluid may be either gases, liquids, fluidized solids, or slurries) just by partially or fully opening the passage-opening. As we know, fluid flow always takes place from a point of higher mechanical energy to a point of lower mechanical energy ( According to Bernoulli’s Principle ).

There is a number of applications of using valve which includes not only to stop  or let the fluid flow but also by means of valve you also can regulate the fluid flow/ rate.
Now Lets talk about the types of valve !!

Fig : Valve Types

Valve Types 

• Gate Valve
• Globe Valve
• Check Valve
• Diaphragm Valve
• Ball Valve
• Butterfly Valve
• Needle Valve
• Foot Valve
• Solenoid Valve

Okay Let see Gate Valve first : 

1) GATE VALVE

• Gate valves (also termed as fully opened or fully closed valve ) are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off.
• Gate valves are designed in such a way so that the drop in pressure is very minimal, when the valve stem is  opened fully ( Reason : Direction of fluid flow doesn’t changes in this case).

Below Mentioned Picture depicts the parts of Gate Vale

The main parts of the all commonly used valves are its  body and  bonnet part. These two parts form the casing that holds the fluid going through the valve. Various other components including these two are as follow :

• Hand wheel
• Stem
• Packing Rings
• Bonnet
• Body
• Gate
• Gate Seats

Know more about Gate Valve from below mentioned slide

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Read Also :  Laminar Flow vs Turbulent Flow

• Globe valve,  are used for regulating  the fluid flow in a pipeline, which is mainly consists of a movable disk-type element and stationary ring seat in a generally spherical body.
• The globe valve is  mainly used for throttling flow control and due to this characteristic this valve is often termed as throttle valve.
• A globe valve is primarily designed to stop, start and regulate the fluid flow.
• The geometry of Globe valve is designed in such a way or you can say s-shaped flow pattern due to which it  creates resistances in fluid flow, results in pressure drop of fluid.

For more details Let see through below mentioned Slides

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3) DIAPHRAGM VALVE

• Diaphragm valves are used on shut-off and throttling service for liquids, slurries and vacuum/gas.
• For handling corrosive fluids diaphragm valve is frequently getting use since fluid stream are isolated from the working parts of the valve, which reduces the chances of corrosion / also the contamination of the fluid.
• In Food / Pharmaceuticals / Biotech industry this valve is commonly used.
• Diaphragm valves offer advantages in certain low-pressure applications not possible with other types of valves.
• Suitable for moderate throttling applications, exhibit excellent leak tight characteristics and offers very less pressure drop.

• Lets see the below mentioned picture : 

4) Quarter-turn valve

a) Ball Valve :

• It comes under the category of  quarter turn valves.
• It consist of  hollow body (perforated in shaped) embedded with pivoting ball use to control fluid flow .
• Ball valves shut off / stop  the  fluid flow by  using a small sphere, or ball, inside the valve body.
• The sphere has an opening inside. When in the “on” position, the opening is in line with the pipe, allowing fluid to flow freely. When in the “off” position, the opening is perpendicular to the flow of fluid, stopping the flow completely.
• In a ball valve, flow is controlled with a lever. Placing the lever perpendicular to the pipe allows fluid to flow. Moving it at 90-degree angle stops the flow.

b) Butter-fly valve :

• Similarly to ball valve it also falls under the category of quarter turn valve.
• Here too flow is controlled with a lever. similarly  by placing the lever perpendicular to the pipe allows fluid to flow. Moving it at 90-degree angle stops the flow.
• Instead of ball here the closing mechanism is controlled by a disc.
• Compare to ball valve , butterfly valve is preferred more due to its lighter weight and less supporting mechanism.
• Disc is made of metal often.  somewhere in industry  instead of metal rubber is getting used for making zero offset in pressure rating.

Lets know more about Ball valve and Butter fly valve by these below mentioned slides : 

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5) Check valve

• Check valves, it is also known as non-return or one-way valves.
• These are designed in such a way so that it  allows fluid – flow in  a single direction (in a pipeline).
• Constructed of a clapper which hangs from a hinge, the clapper shaft or pin, which is mounted to the underside of the bonnet, inside the valve body.
• The basic design of a check valve inhibits back-flow in a pipe-line.
• The degree of opening in a check valve is determined by the flow rate.
• The higher the flow rate, the more open the valve will be until it reaches its maximum, full open position.

Types of check valve :

1. Swing check valve / Disc check valves
2. Ball check valve
3. Diaphragm check valve
4. Stop check valve

Let’s know more about the check valve 

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6) NEEDLE VALVE

Pinch Valve

Pinch valves  is mainly consist of a plastic tube/sleeve. It is made up of reinforced elastomers. The sealing/ closing action is achieved by throttling or pinching this sleeve/tube.Pinch valves are suitable for many applications including liquids, slurries,  fluids having suspended solids, granules and pastes.

A pinch valve is normally opened and has no moving mechanical parts.

Pinch valves offer many benefits over the other types of valves.

• Full bore without moving mechanical parts.
• No risk of blockage and no pressure drop.
• Applications: liquids, gasses, granules, powders, clean liquids, slurries and viscous liquids.

They can be used for handling corrosive fluids as there is no contact between the fluid carried and the actual valve mechanism. Once suitable sleeve material is selected, this valve can work with a variety of fluids. As fluid being carried does not come in contact with the metal parts, these valves can be used for food grade applications also

……Will see about more about valve later.

Thanks !!

ImageCredits : Slide Share

ArticleSource : Wikipedia

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