This article describes a complete detail about shut-off valve and different types of valves. So, a shut-off valve is a mechanical tool used to regulate, control, or direct the different fluids flow, such as slurries, fluidized solids, liquids, or gases, by closing or opening, or partially blocking the flow of fluid. In simple words, it is a device that can control the pressure and flow of different fluids in a process or system. Principally, valves regulate the pressure and flow.
Technically, a valve is like fitting, but it is generally described as a different category. As the valve opens, the liquid or gas runs from high pressure to the low-pressure side.
The oldest and simplest valve is a hinged flap that turns down to prevent fluids (liquid or gas) from flowing in one way. However, when the fluid moves in the reverse direction, the liquid fluid pushes it up. This is known as a check valve because it can block or “stop” the flow of the fluid in one direction. Modern control valves standardize the downstream flow or pressure and work in a complex automated system.
The valves have different industrial applications, irrigation water control, process control, washing machines, dishwashers, and residential applications for pressure control of household faucets. The aerosol also has a built-in microvalve. They also use in different transport and military sectors. In HVAC plumbing systems and other atmospheric air flows, the valves are called dampers. However, the most common types of valve used in compressed air organizations are the ball valve.
Types of Valve:
There are many types of gas valve, but most major types are
1) Gate
2) Diaphragm
3) Check
4) Butterfly
5) Ball
6) Sluice
7) Plug
8) Piston
9) Pinch
10) Parallel Slide
11) Knife Gate
12) Globe.
These types of valves are using in many industrial as well as residential applications. Below has been given an explanation of these.
1) Ball Valve
These types of shut-off valve have a ball plug. This plug acts as a control element. Mostly, ball valves use in different chemical industries. It uses when a combination of closing and throttling requires. Thus, it has excellent liquidity. So, it makes of a two-way globe, and the ball alternates among the elastic valve seats. These valves have a compact structure, low maintenance costs, and no need for lubrication. Ball Valves are existing in full port, reduced, and venture patterns. These types of valves do not use a handwheel to control the flow of liquid but use a wrench to control it.
When this shut-off valve needs to be opened then the handle makes a flat position according to the direction of flow. This generates an angle of 90 degrees with the flow direction when it needs to be closed so you can easily see the status of the valve. These valves can be opened and closed by turning the ball a quarter turn. They have not good throttling. Its size ranges from 6 mm to 900 mm. These are useable for temperatures up to 300° C and pressure up to 500 kg/cm. They widely use in different mechanical industries.
Advantages:
i) It acts quickly.
ii) Ball valves are easy to use.
ii) These have straight flow in any direction,
iii) They have a low-pressure loss.
iv) They require low maintenance costs.
v) These valves design for long service.
vi) It has a reliable seal.
vii) These valves have simple designs.
viii) These have low weight than gate valves.
ix) It has an easy and quick operation.
x) These valves are easy to disassemble.
Disadvantages:
i) Temperature limitation of the sheet material.
ii) Longer “opposite” dimensions between the surfaces.
2) Globe Valves
It works according to the reciprocating movement of the plug or disc. A plug or plug moves in and out inside the valve to stop or allow the flow of the liquid. One disc locates on the seat of the globe valve. This seat may be removed. These valves have a high-pressure drop. Due to the seat arrangement, the globe valve is ideal for the throttle flow, but the throttle should not close if the repeatable pressure drop exceeds 20%. In this shut-off valve, the disc attaches to the stem. These types of valves generally use smooth stems instead of threads. So, these close and open through the assembly of the actuator.
It can operate automatically, electrically, or manually. They use to regulate, start or stop the flow of fluid. So, these types of shut-off valve use in operations that require tightness and flow control. Compared to gate valves, the globe valves can provide better closing performance. It has a high cost as compared to the gate valve. The seats of these shut-off valves have more leakage as compared to the glove valve seat. The disk creates 90 degrees angle with a ring of the valve seat. This angle generates a strong seal between the seat and disc.
Advantages:
i) They have good regularity.
ii) They provide good closing performance than gate valves.
iii) This shut-off valve is very easy to repair.
iv) The maintenance of these valve types is very easy.
v) Globe valve has a shorter stroke as compared to gate valve.
Disadvantages:
i) It has high cost than the gate valve.
ii) These have high weight than gate valves.
iii) These require high power for opening.
iv) It has a high-pressure drop.
3) Gate Valve
Gate valves can only be used for the straight flow of the liquids of gases. They can install in all positions. Gate shut-off valve just uses for closing or opening of the fluids flow. So, it can’t use for the regulation of gases or liquids. These are a type of multi-turn valves that have a rising stem. These types of valve work by moving the disc back and forth on the valve body. You can use one or two discs. So, double-disc valves have good shut-off than a single disc.
It has a stem that may be non-rising or rising. According to the requirements, they have various sizes. This is commonly used in industrial pipelines to stop or isolate a flow rather than adjusting it. So, it can meet the needs of temperature conditions and different pressure, and all connections are available. The structural materials of the gate valve are nickel alloy, bronze, cast iron, ductile cast iron, stainless steel, carbon steel, etc. Duct gate valves are very popular in the chemical industry because they allow precise flow control. These are available in both rising or non-rising stem types.
Advantages:
i) These valve types have a slow operation.
ii) These have low pressure drop during working.
iii) They have a light size.
iv) These have a low-pressure drop.
v) These are inexpensive.
Disadvantages:
i) They are bulky.
ii) These acts slowly than globe or gate valves.
4) Butterfly Valves
The disc acts as a controlling component called a flapper, vane, or blade that rotates horizontally or vertically to allow the liquid to flow on a butterfly valve. These use for the opening, closing, or regulating the flow of the fluids. These valve types use for drainage of buildings, hydropower plants, municipal engineering, and many other applications. They are appropriate for switching or throttling processes with low-pressure loss.
These butterfly valves may have a disc or spiral type. It has automatic, power, and manual operation. Its main advantage is that the seating of the blade is not important. Developed for flow separation. The disc meets an elastic bushing, which ensures tightness at low operational torque. These have a compact as well as a simple structure. These are preferable due to their low price and lighter weight than other shut-off valve types. The disk locates in the middle of the pipeline. A rod passes by the valve disk and reaches to the actuator on the valve outer. The rotary actuator enables the valve disk to move at 90 degrees or parallel to the fluid flow.
Advantages:
i)It acts quickly.
ii) It has lightweight.
iii) These are easy to install.
iv) It requires very low maintenance.
vi) These have a low cost.
vii) It has a quick operation than other types of the shut-off valve.
viii) These are simple as well as reliable.
ix) It does not generate solids.
x) It has a low-pressure loss.
5) Diaphragm Valves
The diaphragm valve has a flexible diaphragm, bonnet, and body. Opening the valve lifts the diaphragm, and closing the valve, presses the diaphragm firmly against its bottom. This shut-off valve has two types.
- Straight type.
- Wire type.
Wire diaphragm valves require a relatively small push and shear stroke. This can extend the life of the diaphragm. These are most common in industries.
Straight diaphragm valves are appropriate for the fibrous suspension, viscous fluids, and handling slurries. The diaphragm cannot completely lift off the weir with some diaphragm valves, allowing small flow rates to be precisely controlled. The diaphragm makes of buna, neoprene, or rubber. The sizes range from 3 mm to 600 mm. These can use at pressures of up to 20 kg / cm2 and temperatures of 2200 ° C. These types of valves are made of corrosion-resistant alloy, stainless steel, or cast iron.
6) Plug Valve
These valves have a conical or cylindrical “plug” that can rotate within the valve body and control the flow of the fluid. The plug of a plug valve has one or more hollow channels that run through the sides of the plug so that when the valve can open, the liquid can flow through the plug.
These are the oldest types of shut-off valve. These use for opening or closing the flow of fluid. Its major components are the cover, cone, and body. It has a cylindrical or conical shape. The plug has a notch to allow the liquid to flow. It provides a straight-line flow. It opens or closes with just a quarter turn. Thus, it has at least one port to divert the flow. It can be lubricated or not.
Advantages:
i) These have a Simple design.
ii) These have a low cost.
iii) They have high capacity.
iv) They take quick action.
v) Easy to operate.
Plug valve has the following major types.
- Multi-Port.
- Non-lubricated.
- Lubricated.
- Diamond Port.
- Round Port.
- Rectangular Port.
7) Needle Valve
It has a plug. This plug has a conical shape, and it can place very precisely on the seat. The flow of the fluid regulates by the annulus between the seat and the conical plug body. These types of shut-off valve use for accurate and small flow rates. It has a similar design to that of the globe valves. The needle valve design enables very precise flow control of small diameter piping arrangements. They got their name from the machining seats and their conical disc.
These valves use to control hydraulic fluids or air to reduce pressure fluctuations. They have structural materials like stainless steel, brass, or bronzes, etc.
8) Angle Valve
These types of valves have the same design as globe valves. In the case of these, the outlet and inlet end is at an angle of 900. The steam axis is aligned with one end.
Advantages:
i) These types of valves have a low-pressure drop.
ii) They can also use for corrosive fluids.
iii) It may have a split or a single body.
9) Pinch Valve
These are also known as clamp valves. It has a replaceable sleeve. It has linear movement. These types of valves used to stop, adjust or start the flow of fluids. It has a tube that knows as a pinch tube. This Rubber tubing and a pinch mechanism are used to control the liquid.
These are suitable for handling slurry, liquid, and particulate systems with large amounts of solid materials. Thus, it has a working mechanism that is completely exceptional from the liquid. The sleeve makes of plastic or rubber. These are not appropriate for vacuum operation.
10) Slide Valves
It uses to control the low-pressure flow of different fluidized solids, suspensions, liquids, and gases. There are two parallel main seats. So, the disc slides between these slides. This disc behaves as a gate, and the pressure difference provided by the slide valves is very small. It has a size ranges from 50 mm to 1500 mm.
11) Flush Bottom Valve
These valves are special types of shut-off valve for draining viscous materials, sludge, abrasives, or semi-solid media from containers, reactors, and pipes.
Widely used in the manufacturing industry to drain material from tanks. They have a size range from 25 mm to 150 mm. These can also use to drain dry solids from the bottle.
12) Solenoid Valves
It works as a control valve. These are suitable for slide stems and on-off globe valve.
These use for service requests for emergency shutdowns. They have a size range from 1 mm to 100 mm. It can use for ultra-high pressure 650 kg / cm2 and temperature from -250 ° C to 800 ° C. These types of shut-off valve are made of materials such as plastic brass, aluminum, stainless steel, cast iron, etc. Solenoid valves are often used in low-temperature processes.
13) Check Valve
These types of valve are sometimes indicated as non-return valves. It prevents backflow in the pipeline by maintaining a one-way flow of liquid at all times. It works automatically. Some disc check valves are spring-loaded for a high-speed process (minimum opening pressure must be specified). So, spring-loaded check valves require for vertical flow.
For more reading about check valves and its types, click the below-given diagram and read more.
Check Valve has the following types.
Swinging Check: Wafer and Swing stop the backflow utilizing disks that can rotate into the seat. It should only be used for vertical or horizontal forward flow.
Piston Check: Spring and Piston checks use a spring plunger or piston to prevent backflow.
Ball Check: This check valve has a ball. When the forward flow slows down, the ball will slide through the hole. Suppose a sphericity test for semi-solids (like sewage and pulp).
Tilting Disc Check: It is similar to swing check valves, but in most installations, the backflow minimizes slamming and reduces vibration and noise.
14) Flow Regulation Valves
These types of shut-off valve keep the flow constant regardless of changes in pipeline pressure. When the pressure varies on any side of the flow, the diaphragm drives the poppet valve. It closes and opens to keep the flow constant.
15) Back Pressure Regulation Valves
It comes with a piston or spring-loaded disk. Whenever the system pressure overdoes the pressure utilized by the spring, the piston rises, and the valve opens. The diaphragm transfers pressure to the piston or disc. These have the same design as pressure relief valves.
16) Pressure Regulation Valve
It uses for the regulation of steam pressure. These types of valves are too common in different industries.
Applications of Valves:
- It uses in the different chemical and fertilizer industries for controlling the flow of fluid.
- It also uses in the food industries.
- Water Valve uses for residential purposes such as to control water from different tanks.
- These are widely used in the agricultural field such as spray cans have a valve for controlling spray.
- They also use in hydroelectric power plants.
- They use with different types of pumps.