What is a Valve? And Different Types of Valves Explained

What is a valve? What are the different types of Valves in the market?

A valve is a device that regulates, directs or controls fluid flow (gas, liquid, fluidized solids or slurry) by opening, closing, or partially blocking various aisles. Valves are technical fittings but are usually discussed as separate categories. In an open valve, the fluid flows in the direction from high pressure to low pressure.

The simplest, and very ancient, the valve is simply a freely hinged flap which drops to obstruct fluid (gas or liquid) flow in one direction but is pushed open by flow in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.

Valves have many uses, including controlling water for irrigation, industrial needs to control processes, use of housing such as on / off and pressure control for dishwashing and clothing and taps at home. Even aerosols have tiny valves. Valves are also used in the military and transportation sectors.

  

In HVAC airways and other air currents near the atmosphere, valves are instead called dampers. However, in compressed air systems, valves used with the most common type are ball valves.

FUNCTIONS OF VALVES ARE:
1. Stop and start flowing.

2. Reduce or increase flow.
3. Control the direction of flow.
4. Adjust process flow or pressure.

5. Lighten the pipe system from certain pressures.

Now, let’s look at how many types of valves are there in the market: -

      1. Gate Valve

Gate Valve is a type of sliding valve. In the gate valve, the closing member is a metal gate. The gate slides down to close the valve. In a fully open condition, the flow area is the same as the pipe area and hence, there is a negligible pressure drop in the valve.

The gate valve should ideally be used as an on-off valve. It is not recommended to use it as a throttling valve because, in partially open conditions, gate erosion may occur. In partially open compositions, due to vibration, the valve is subjected to rapid wear.

 Also, during closure and openings, there is a lot of friction and hence, opening and closing the valve quickly and often is impossible.

This valve is used in the petrochemical industry due to the fact that they can work with sealing metals.

2. Plug Valves

Similar to ball valves, the plug valve is also a quarter-turn type of valve. This valve consists of a plug that can be cylindrical or cone-shaped. The plug has a through the slit that remains parallel to the flow in open conditions.

 When the plug is rotated 90 degrees, this slit becomes perpendicular to flow and the valve is closed.

The valve plug is very suitable for handling liquids with suspended solids, slurry etc.

The Plug valve is mainly used for on-off applications. When used for deceleration purposes, the pressure drop through the valve is higher due to misalignment between the direction of flow and the direction of opening (gap).

3. Butterfly valve

The butterfly valve is the simplest but most versatile valve. They are quarter-operated valves that are commonly used in various industries for various applications. A quarter-turn operation ensures fast valve operation.
 In open conditions, there is a minimum barrier to fluid flow through the valve when the flow passes through the disk aerodynamically. This results in very little pressure drop through the valve.

Due to its unique mode of operation, the valve can be actuated easily without the need for high torque and wear & tear.
 Due to lack of friction, the use of large actuators can be avoided. Another advantage offered by a butterfly valve is its compact size. The valve is quite compact, resembling a metal disc. 
This makes their installation very easy. They can be used to deal with slurry and liquid with suspended solids because there is no cavity for the deposition of solid particles in the valve body.

4. Globe valve

Globe valve is a type of linear motion valve and is usually used in on-off and throttling applications. 
In the globe valve, fluid flow through the valve follows the S-path. Because of this, the direction of flow changes twice which results in a higher pressure drop. 
Because of the other advantages offered by them, they are widely used in applications where pressure drop through valves is not a controlling factor.

These valves are generally not used in excess of sizes greater than NPS 12 (DN 300) because large forces are applied to the rod to open or close the valve under fluid pressure. Globe valves require high pressure on the seat to remain closed when the fluid puts pressure from the bottom of the disc.

5. Pinch Valve

The pinch valve consists of a plastic tube/sleeve consisting of reinforced elastomers. Sealing/closing actions are achieved by strangling or clamping these casings/tubes.
 The pinch valve is best suited for handling slurries and liquids that have suspended solids. Pinch valves offer many benefits over other types of valves.
 They can be used to handle corrosive liquids because there is no contact between the fluid carried and the actual mechanism of the valve. After the suitable sleeve material is selected, this valve can work with various liquids. Because the liquid carried does not come into contact with metal parts, this valve can also be used for food-grade applications.

Generally, the pinch valve is suitable for low-pressure applications. When used with abrasive slurry, they must be used as an on-off valve; if used for throttling purposes, the sleeve will be worn out.

6. Disc Check Valve (non-return valves)

Disk check valves also referred to as non-return valves allow flow to pass through only in one direction and stop flow in the opposite direction.
Because of this unique directional nature, the disc check valve is basically used for several important applications in the steam system.

There are four main types of disc check valves as follows –

 1. Lift Check Valve

2. Swing Check Valve

3. Spring Check

4. Diaphragm Type Check 

Contact Us: Parth Valves And Hoses LLP

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