Types of valve

 

Types of valve 

There are many different types of valves, some types are discussed below.

Gate Valve

Gate valve resembles to a gate so their name is gate valve. Gate valve are used mostly for on off services. Gate valve is made up of a plate like a gate, that moves up and down on a saeat to allow the flow or stop the flow. 

Gate valve are sliding motion or linear motion valves. Stem of gate valve moves perpendicular to the direction of fluid flow.

Applications of Gate valve 

Gate valve can work well in high temperature and pressure applications.

 It is preferred to be used for clean fluid flow control.

Gate valves are fully sealed.

Gate valve have low pressure drop.

Gate valves are not considered good to be used for slurry or viscous fluids.

Gate valve seat disc wears in partiality open position.

Gate valve causes vibration.

Globe Valve

Globe valve is made up of a plug or disc that moves up and down on a sear to allow or stop the flow. Travel path in globe valve is short.

Globe valve causes high pressure drop.

Applications of Globe valve 

Globe valve are mostly used as throttling valve.

Globe valve is suitable in high temperature environment.

Globe valve is a fast valve. 

Its responses is good.

Globe valve disadvantages is same as gate valve that seat disc wears in partial open condition.

Ball Valve

Ball valve seat resembles to a ball because its round sphere so its called ball valve. Ball valve are mostly used as shut off services.

Ball valve can be used for liquids and gases. Ball valve applications are for slurries viscous fluids and for clean fluids, its a multi purpose valve. Ball valves are useful in the hugh temperature and pressure environment applications.

Ball valve are low pressure drop valve.

Ball valve operation is quarter turn.

Ball valve maintenance is easy.

Torque of the ball valve is low.

Ball valve are smallmostly and less weight.

If we consider the disadvantages of ball valve, Ball valve uses PTFE seats that wear with time specially when used as throttling valve. Ball valve may stuck due to corrosion on ball and sear.

Butterfly Valve

Butterfly valve are made up of a disc which rotate 90-degree in a section of pipe to open or close the flow of fluid. A stem is used to support the disc from both sides. Butterfly valves are classified as rotary movement valves.

Butterfly valves are used in applications where large flow. These avlces are used for low pressure applications.There are chances of leakage if sealing around disc is wear.

Butterfly valves are simple in construction.

Butterfly valves are compact valve.

These are quick opening valves.

Butterfly valve are less costly.

These are less weighted.

Only disadvantage of butterfly valves is leakage because these are not tight shutoff.

Plug Valve

It consist of body,plug and cover. The plug shape is tapered or cylinder shapeed. bore in plug is connected between inlet and outlet,when valve is in open position. So fluid can flow easily in straight line.

Applications of plug valve

  The plug valves are  used in petrochemical industry, chemical industry and refineries.

plug valve are used for applications where on off services are required.

 

Advantages of plug valve 

Plug valves are small in size so need small headroom. These are available in many types of materials. These types of valve are quick open.

Low pressure drop is another benifit of plug valve. These valve are sealed so shuoff position is tightly sealed.

Disadvantages of plug valve

 Plug valves have only one disadvantage that is  galling.

Diaphragm Valve

The flexible diaphragm is connected to a support member known as compressor,which represents the closure member.When the valve is opened the diaphragm is lifted out of the flow path and the fluid has a smooth streamlined flow.When the valve is closed the diaphragm is tightly seated against the seat in the body known as the wier. The diaphragm is of NEOPRENE.

Application - Used for corrosive liquids at low temp and pressure.

Diaphragm Valves Advantages - The diaphragm completely keeps the working parts in isolation from the process fluids.Simple in construction,easier to operate and maintain.

Disadvantages of Diaphragm valves- Not for high temp and pressure.

Check Valve

A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid to flow through it in only one direction.

Check valves are generally installed in pipelines to prevent backflow. A check valve is basically a one-way valve, in which the flow can run freely one way, but if the flow turns the valve will close to protect the piping, other valves, pumps etc.

A check valve relies on a pressure differential to work. They require a higher pressure on the input side of the valve than the output side to open the valve. When the pressure is higher on the outlet side (or the input side pressure is not high enough), the valve will close.

The check valve prevents stored energy from making its way back into the pump, an especially important task when there is stored energy in the accumulator and the pump is not even running. Energy stored in an accumulator can be dangerous or damaging and must be controlled for hydraulic systems to be safe and reliable.

For example, failing check valves will start to vibrate and even lose some internal parts when problems begin to arise. Other symptoms of check valve failure include reverse flow and excessive component wear and damage. Check valves will also emit noises as they start to break down.

Stop check Valve

A stop check valve is a combination of a lift check valve and a globe valve. It has a stem which, when closed, prevents the disk from coming off the seat and provides a tight seal (similar to a globe valve). Figure : Stop Check Valve. When the stem is operated to the open position, the valve operates as a lift check.

 stop-check valve is essentially, two valves built into one. It can act as a globe valve to isolate or control the flow rate

Safety relief Valve

A relief valve or pressure relief valve is a type of safety valve used to control or limit the pressure in a system; pressure might otherwise build up and create a process upset, instrument or equipment failure, or fire. 

Pressure relief valves (safety relief valves) are designed to open at a preset pressure and discharge fluid until pressure drops to acceptable levels. ... When the force of the steam pressure acting on the valve exceeded the force of the weight acting through the lever arm the valve opened.

The primary function of Safety Relief Valves is the protection of life, property and environment. A Safety Relief Valve is a (safety) device designed to protect a pressurised vessel or system against over-pressure should all other safety systems fail.

Here are six factors that must be considered when selecting and sizing safety or pressure relief valves.

1. Connection size and type. The valve size must correspond to the size of the inlet and discharge piping. ...
2. Set pressure (PSIG) ...
3. Temperature. ...
4. Back pressure. ...
5. Service. ...
6. Required capacity.