Definition of Valve, Types and Functions

A valve or commonly called a valve is a device that regulates, directs, or controls the flow of a liquid (gas, liquid, fluidized solids) by opening, closing, or partially closing the flow path.

Valve in everyday life, the most obvious is in water pipes, such as faucets for water. Other familiar examples include gas control valves on stoves, small valves installed in bathrooms, and much more.

Valves play an important role in industrial applications ranging from the transportation of drinking water to controlling ignition in rocket engines.

The valve can be operated manually, either by the handle, pedal lever, and others. Besides being able to be operated manually, the valve can also be operated automatically by using the principle of changing the flow of pressure, temperature, etc. These changes can affect the diaphragm, spring, or piston which in turn activates the valve automatically.

Types of Valves that are often used:

1. Gate valve

A gate valve is a type of valve that is used to open the flow by lifting the closing gate which is round or rectangular.

Gate Valve is the type of valve that is most often used in piping systems. Its function is to open and close the flow.

The gate valve is not to adjust the rate of a fluid flow by opening half or a quarter of its position, so the position of the gate on this valve must be completely open (fully open) or completely closed (fully closed). If the position of the gate is half-open the flow will be turbulent and this turbulence will cause:

  • a. There will be the erosion of the corners of the gate.
  • This turbulent fluid flow rate can erode the corners of the gate which can cause erosion and ultimately the valve cannot work perfectly.
  • b. There has been a change in the position of the closing gate holder.

The closing gate will swing towards the seat position so that over time its position will change to the seat so that when the valve closes the closing gate will not be in the right position, so it can cause passing.

There are 3 types of gate valves:

  • Rising Stem Gate Valve, if the handwheel is operated it goes up and the stem also goes up.
  • Non-Rising Stem Gate Valve, if it is operated the handwheel is fixed and the stem is also fixed.
  • Outside Screw & Yoke Gate Valve, if the handwheel is operated it stays but the stem goes up.
  • Rising Stem & Non-Rising Stem are used for not too high pressure, and not suitable for vibration. Outside Screw & Yoke Gate Valve is very suitable for high pressure. Usually, OS & Y is widely used in oil fields, high fields, high temperatures. Because on OS & Y stems up or down can be used as a marker. For example, if the stem is high it indicates the position of the valve is fully open. The body & bonnet on the gate is made of the same material.

Advantages of using Gate Valve :

  • Low-pressure drop full opening time
  • Very tight and quite good full closing time
  • Free of contamination
  • As the Gate is full closing, so there is no more pressure. Suitable when going to do service/repairs on pipes

Disadvantages of using Gate Valve:

  • Not suitable for use for half-open, because it will cause turbulence so that it can cause erosion and change the position of the gate on the seat
  • To open and close the valve takes a long time and requires high torque/torque
  • For sizes 10 “and above it is not suitable used for steam.

2. Globe valve

Global Valve is used to adjust the size of the fluid flow rate in the pipe (throttling). The basic principle of operation of the Globe Valve is the perpendicular movement of the disc from its seat. This ensures that the ring-shaped space between the disc and seat ring is incremented as close as the valve is closed.

By simply turning the valve handle, the amount of substance flowing through the valve can be adjusted.

The valve seat is parallel to the flow, making the globe valve efficient when adjusting the size of the flow with minimum disc and seat erosion. However, the resistance inside the valve is quite large.

The design of the Globe Valve is such that it forces a change in the direction of the flow of substances in the valve so that the pressure drops drastically and causes turbulence within the valve itself. Therefore, it is not recommended to install Globe Valve in systems that avoid

pressure drop, and systems that avoid resistance to flow.

There are three main types of Globe Valve body design, namely: Z-body, Y-body, and Angle-body:

  • Z-Body design is the most common type that is often used, with a Z-shaped diaphragm. Horizontal disc mount position and disc rod movement perpendicular to the axis of the pipe or disk mount. The symmetrical shape makes it easy to manufacture, install and repair.
  • The Y-Body design is an alternative to high-pressure drop. The position of the disk holder and stem is at an angle of 45˚ from the direction of the fluid flow. This type is very suitable for high pressure
  • Angle-Body design is a basic modification of the Z-Valve. This type is used to transfer flow from vertical to horizontal.

Various forms of Disc/plug from Globe Valve:

  • Plug Type Disk
  • Regulating disk
  • type Flat disk
  • type Soft seat disk
  • type Guide disk type
  • The advantages of using a Globe valve are:
  • The ability to close well.
  • Throttling ability (adjusting the flow rate) Fairly good.

The main disadvantages of using Globe Valves are:

  • Higher pressure drop compared to
  • large size Gate Valve Valves require sufficient power or larger actuators to operate

3. Angle Valve

Like the globe valve, the angle valve is also used in situations where throttling is required. However, the angle valve is made with a 90° angle, this is to reduce the use of a 90° elbow and additional fittings. used to change the flow by 90 degrees. This valve can also be used instead of elbow

4. Ball Valve

A Ball Valve, or also knowing as van bi điều khiển khí nén is a valve or valve with a flow controller in the form of a spherical disc (like a ball/slice). The ball has a hole, which is in the middle so that when the hole is in a straight line or line with both ends of the Valve, the flow will occur.

But when the valve is closed, the position of the hole is perpendicular to the end of the valve, then the flow will be blocked or closed.

Ball valves are widely used because of their ease of repair and ability to withstand high pressures and temperatures. Depending on what material they are made of, Bal Valves can withstand pressures of up to 10,000 Psi and temperatures of around 200 degrees Celsius.

Ball Valves are used extensively in industrial applications because they are so versatile, they can withstand pressures up to 1000 bar and temperatures up to 482°F (250°C). They usually range in size from 0.2-11.81 inches (0.5 cm to 30 cm).

Ball valves can be made of metal, plastic, or ceramic. The ball is often chrome plated to make it more durable.

There are 2 types of ball valves, namely:

  • a. Full bore ball valve

The full bore ball valve is a type of ball valve with the diameter of the ball bore equal to the diameter of the pipe. Types of full bore ball valves are usually used in blowdown, piggable line, production manifold, pipeline, etc.

  • b. Reduced bore ball valves

Reduced bore ball valves are a type of ball valve whose ball bore diameter is not the same as the pipe size. The minimum diameter of the reduced ball valve is one size lower than the actual pipe diameter. For example, the diameter of the pipe is 4 inches and the diameter of the ball valve is 3 inches.

And there are 2 types of paths on the ball valve, full bore, and reduced bore.

Usage (Function) Ball Valve:

  • Flow control / Flow
  • control Pressure control/pressure control
  • Shut off
  • Suitable for high pressure and temperatures / high pressure and temperature

Advantages/advantages of ball valve:

  • A very low-pressure drop
  • Low leakage/rarely leaking
  • Small in size and the ball valve is not so heavy when compared to other similar valves
  • Easy to open and not easily contaminated.

Disadvantages/disadvantages of the ball valve:

  • Seats can be damaged due to friction between the ball and the seat. 
  • Quick opening of the handle can cause a water hammer/water hammer in the system resulting in a large pressure that can damage the system/connection and pipe walls

The function of the “Ball Valve” is to control the flow. For this type of valve, the method of opening and closing the path uses a ball (disk on a butterfly valve) with a hole in the middle. If the position of the ball is in the lane, the valve is in a closed condition, and vice versa, if the position of the hole in the middle of the ball is in the lane, the valve is in the open position.

Often used in hydrocarbon processes, ball valves can regulate the flow of gas and steam,

especially for low pressures. This valve can be quickly closed and is tight enough to hold

fluids. The ball valve does not use a handwheel but uses the ankle to open or close the valve at an angle of 90°. Its simple design minimizes pressure drop when the valve is fully opened.

5. Plug/cock Valve

The purpose of the plug valve is to fully open and fully close (isolation or on/off control).

To control (open and close) the flow in the plug valve, the plug has a gap or hole through which the flow passes. When the handle is turned to the open position, the plug will rotate rotationally about the seat and the gap will pass the flow. However, when the handle is turned in the close position, the plug will rotate rotationally to the seat and the part that does not gape will block the flow so that the flow will stop.

Same as a ball valve, but the inside is not a ball, but a cylinder. Because there is no space in the valve body, it is suitable for fluids that are heavy or contain solid elements such as mud.

Other types of valves that are still included as plug valves are:

Three-way plug valve: a type of plug valve that has 3 ports (connections), 1 for the inlet and 2 for the outlet. By using this valve, we can easily direct the outlet to the desired flow/pipe.

Four-way plug valve: Usually used in cooling water fluid that passes through a heat exchanger, where the cooling water flow can be easily reversed to clean the heat exchanger from impurities (fouling, sediment, solids).

6. Check Valve

A check valve is a tool used to make fluid flow only in one direction or to prevent reversed flow/backflow. to allow fluid to flow in only one direction and prevent flow in the opposite direction. does not use handles to regulate flow, but

uses gravity and pressure from the fluid flow itself. Because of its function that can

prevent backflow (backflow), Check Valve is often used as safety of 

equipment in a piping system

Applications of this type of valve can be found at the outlet/discharge of the centrifugal pump.

When the fluid flow rate matches its direction, the flow rate will cause the plug or disk to open. If there is pressure coming from the opposite direction, the plug or disk will close.

Check Valve has a significant difference from Gate Valve and Globe Valve. This valve is designed to prevent backflow.

There are several types of check valves, but the two most common are Swing Check and Lift Check. Swing Check Valves are usually paired with Gate Valves, while Lift Check Valves by some manufacturers are used to replace the Ball Valve function as Ball Check Valves. Check Valve does not use a handle to regulate flow but uses gravity and pressure from the fluid flow itself. Because of its function that can prevent backflow, Check Valves are often used as a safeguard for equipment in piping systems.

There are 3 (three) types of check valves

  • a. Swing Check Valve 

The swing check valve consists of a disk the size of the pipe used and is designed to hang on a hinge pin at the top. If there is a forward flow, the disk will be pushed by the pressure so that it opens and the fluid can flow into the outlet channel. Meanwhile, if there is a reverse flow, the fluid pressure will push the disc to close tightly so that no fluid flows. The higher the backpressure, the more tightly the disc fits into the cradle.

Usage: One-way flow

Advantages: When you open it lightly, the low-pressure drop/pressure loss is very low, the cost is cheap

Disadvantages: Leakage is very high and flow is low because it is disturbed by the presence of

obstacles

  • b. Lift Check Valve

Use for steam, gas, or liquid fluids that have high flow.

In its configuration, it is similar to a globe valve, except that the disk or valve rotation can be manipulated while the lift check valve cannot (because the globe valve is a type of rotary valve and control valve).

The inlet and outlet ports are separated by a conical plug that sits on the amount, usually made of metal. When there is forward flow, the plug will be pushed by the fluid pressure so that it is released from the holder and the fluid will flow into the outlet channel. Meanwhile, if there is a reverse flow, the fluid pressure will place the plug on the holder, the greater the pressure, the tighter the position of the plug on the holder, so that the fluid cannot flow.

the material of the plug seat is metal, this takes into account the very little leakage rate of the check valve. Generally, lift check valves are used for gas fluid applications because of the small leakage rate. The use of this lift type check valve in the industry is to prevent condensate backflow into the steam trap which can cause corrosion in the steam turbine. The advantage of using a lift check valve is that it is simple in design and requires little maintenance. The disadvantage is that the installation of a lift-type check valve is only suitable for large diameter horizontal pipes.

  • c. Backwater check valve

Backwater valves, widely used in underground water drainage systems that prevent backflow from the sewer during a flood. When flooded the sewer will be full and high pressure so that it allows backflow, by using a backwater valve, this can be handled properly.

  • d. Swing Type Disk Check Valve

The use of swing check valves and lift check valves are limited to large pipes (diameter DN80 or more). so as a solution is to use a disk check valve. By using a disk check valve, tubing with a size that is conical on one side can be used so that it can be applied to smaller pipes.

  • e. Check valve disc

Disk Check valve consists of body, spring, spring retainer, and disc. The working principle is that when there is forward flow, the disk will be pushed by fluid pressure and push the spring so that there is a gap that causes fluid flow from the inlet to the outlet. Conversely, if there is a reverse flow, the fluid pressure will push the disk so that it closes the fluid flow

The difference in pressure required to open and close this type of valve is determined by the type of spring used.

In addition to standard springs, several spring options are available:

No spring – Used where the pressure difference across the valve is small.

Nimonic spring – Used in high-temperature applications.

Heavy-duty spring – This increases the required opening pressure. When installed on a water feed boiler line, it can be used to prevent boiler steam from flooding when they are unpressurized.

  • f. Split disc check valve

The split Disk check valve consists of a disk whose center is a shaft that allows the disk to move as if it split in two when pushed from the right direction (forward flow) and closes tightly when pressed from the wrong direction (reverse flow).

7. Screwed Down Return Globe Check Valve

The model is almost the same as a globe valve, the difference is that there is an additional housing/casing that supports automatically if media are flowing on the valve.

8. Butterfly Valve

Butterfly Valve has a unique shape when compared to other valves.

The Butterfly uses a circular plate or disk operated with the ankle to

fully open or close at an angle of 90°. This disk remains in the middle of the flow and is

connected to the ankle via a shaft. When the valve is closed, the disc is perpendicular

to the flow direction, so the flow is blocked, and when the valve is open the water is parallel to the flow, so that substances can flow through the valve.

The battery valve has minimal turbulence and pressure drop.

These valves are great for on-off or throttling operations and are great for controlling the flow of large quantities of liquid or gas. However, these valves are usually not very tight and must be used in low-pressure situations/systems.

9. Diaphragm Valve

A diaphragm valve can be used to regulate flow (throttling) and can also be used as an on/off valve. Diaphragm valves are reliable in handling rough materials such as fluids containing sand, cement, or mud, as well as fluids that have corrosive properties.

10. Solenoid Valve

In this type, the valve opening and closing is an electro-magnetic circuit generated by a coil through which an electric current passes.

11. Motor operated Valve

This type of valve, the stem (stem) valve is connected (joint/couple) with an actuator in the form of an electric motor. In practice, some use AC electricity (alternating current = alternating current electricity) and some use DC electricity (direct current = direct current electricity).

12. Pinch valve

Pinch valves are used to handle muddy fluids, deposits, and those that have a lot of solid particles and fluids that tend to leak.

13. Safety/Relief valve

Safety/Relief valves have a very different function from other valves. This valve is specially designed to release excess pressure in piping equipment and systems. To prevent damage to equipment, and more importantly injury to workers, the relief valve can release the pressure build-up before it gets too extreme.

The relief valve uses a steel spring (see picture below), which will automatically open if the pressure reaches an unsafe level. The pressure level on this valve can be adjusted, so it can be determined at what pressure level this valve will open. When the pressure returns to normal, the relief valve will automatically close again.

The safety valve is a type of valve whose mechanism automatically releases substances from a boiler, pressure vessel, or a system when the pressure or temperature exceeds a predetermined limit.