Types-of-valves

Valves are essential for the regulation of fluid flow and to open and close the fluid flow path. Various valves are used in different applications, and they all have their pros and cons.

A few valves have been discussed in this article, along with their advantages and disadvantages. The working principles and components have also been discussed.

1. Butterfly Valves

A butterfly valve is a quarter-turn valve used to regulate the passage of fluids through a pipe. Some level of control is also provided to the fluid.  The design is such that complete flow is provided but with a set amount of efficiency. You cannot get positive shut-off from butterfly valves. But now it’s possible to build butterfly valves with tight closure thanks to high-temperature ratings and the latest polymers.

Several components of a butterfly valve include a metallic disc or butterfly disc, an outer body/casing, an actuator, and a positioning plate. A strong seal is made due to the packing. This seal surrounds the stem and protects the stem. The disc is mounted on a rod and stops fluid passing when the valve is closed.

The disc moves depending on the opening or closing of the valve. When the disc rotates perpendicular, the valve is entirely open, and a large amount of fluid can pass through the pipe. A seat is also fixed on the body. This seat gives a proper seal to the body. Most manufacturers provide an additional seal in case the seat gets damaged.

Butterfly Valves Advantages

Butterfly valves are widely used for several reasons. Some advantages of check valves are as follows:

  • Butterfly valves are lightweight with a wafer-form body. The low weight and compact size make them favourable for use in many applications.
  • Butterfly valves are relatively cheaper than other valves. This may be because of the low weight and that a small number of components are used in their construction.
  • The installation costs are low.
  • The design is not complicated. A small number of parts are used in the construction of butterfly valves.
  • It is reasonably convenient and easy to repair butterfly valves. So we can say they are maintenance-friendly.
  • Butterfly valves can transfer mud with a little fluid deposit in the outlet of the pipe.

Butterfly Valves Disadvantages

There are a few disadvantages of using butterfly valves. They are discussed below:

  • A part of the butterfly disc is always facing the flow even if it’s completely open. So there’s still a pressure switch over the valve no matter what the setting is.
  • The sealing is not as good as other valves.
  • When butterfly valves are used, throttling is limited to low-pressure drop systems.
  • Sometimes, the choked flow may occur when using a butterfly valve.

2. Ball Valves

Ball valves originated in the 1950s, and since then they have gained popularity. Ball valves consist of a ball with a hole in it. Whenever the pipe and hole are aligned, water or other fluids can pass through the pipe. However, when the ball rotates or turns, and the hole is not in line with the pipe, there is no more fluid passage through the pipe.

There are some types of ball valves like flanged, hydraulic, standard, vented ball valves etc. Ball valves consist of a valve stem, a valve seat, O-rings, and a valve housing. The valve seat can either be automatically operated or manually operated.

Ball Valves Advantages

Ball valves have some significant advantages that make them a part of a variety of applications. Some benefits to using ball valves are as follows:

  • Ball valves are reliable for applications in corrosive media and liquids with low boiling points because they don’t get stuck on the go.
  • The sealing system is excellent on both sides.
  • Ball valves have the lowest flow resistance.
  • Ball valves open and fast reasonably fast. Some of them open and close in 0.05- 0.1 seconds.
  • The ball valves can be sealed entirely even if pressure and temperature are both high.
  • Ball valves are compact and don’t weigh a lot. This is a favourable feature for valves. Some may even say that valves have the most reasonable or ideal structure among all valves.
  • They work well even without the use of a lubricant.
  • The welded body of ball valves can be buried directly into the ground, so the valve’s internals doesn’t erode.
  • Ball valves are long-lasting and will last you a minimum of 10 years!

Ball Valves Disadvantages

While ball valves are very beneficial, they also have certain advantages:

  • The valve seat in a ball valve is usually made up of Teflon. Teflon has a very high coefficient of expansion and is sensitive to cold flow. It also has low thermal conductivity. If the ball valve’s design isn’t made keeping in mind the limitations of Teflon, you might be faced with problems. When the seat material hardens, the seal may not be as effective.
  • The Teflon used in the construction of ball valves does not work well with temperatures above 180 degrees. The sealing material ages when the temperature is high.
  • The adjustment performance isn’t good as compared to other valves.

3. Globe Valves

A globe valve is a type of valve that is linear motion and used to regulate, stop, and start liquid or fluid flow. You can detach/remove the disc entirely from the fluid’s path or place it in the path of fluid to stop the flow. The disc moves at 90 degrees angle to the seat when the valve is opening or closing.

There is annular space between the disc and the seat ring. This space is produced by movement, and space is removed as soon as the valve shuts off. So throttling is possible when globe valves are used. In other words, flow can be controlled using globe valves.

Fluid can either be above or below the disc. This depends entirely upon the area or application of use. You can arrange the globe valves in a way so that the disc closes against the flow of liquid. When the disc is closed against the fluid flow path, the kinetic energy resists closing and allows the valve to open.

Globe Valve Advantages

  • Globe valves are wear-resistant as there is very low friction between the valve flap and sealing surface.
  • The low friction makes the opening and closing process effortless.
  • Globe valves are very easy to maintain because there is only one sealing surface.
  • Asbestos and graphite have been used as fillers here. So they can resistant high temperature.
  • Globe valves have a better shut off than gate valves.
  • Wear and tear are relatively less in these valves as compared to others.
  • An automatic actuator usually operates the globe valves.

Globe Valves Disadvantages

  • The minimum flow resistance of globe valves is generally higher than other types of valves.
  • The speed at which the valve opens is also low.
  • Globe valves can be expensive as compared to gate valves.
  • They weigh more than other valves with the same pressure value.
  • You may face a high head loss if the valve is obstructed.

4. Gate Valves

Gate valves shut the inflow and outflow of fluids by the insertion of a rectangular gate to the liquid’s path. A wedge type structure can also block flow. They require very little space in the pipe. When the gate is opened fully, all the fluid can freely pass without the slightest resistance and low-pressure drop. You’ll find that these valves are mainly used with large pipe diameters, and they are simple in design with not so complex construction.

Gate valves have three components called the bonnet, the body, and the trim. The bonnet contains all the moving parts and is attached to the body. The body is usually attached to the body with the help of flanges, screws, or connections. The bonnet is connected to the body with bolts, so it allows effortless cleaning. The trim includes a stem, gate, disc, seat rings, and the wedge.

The three components work in unison to give you the best of results. The working principle is relatively simple. The stem is rotated whenever the handwheel is turned. This results in vertical movement of the gate by the threads. It takes a full 360 degrees turn to close and open the valve. To put in simple words: when the gate is put in the path of fluid, the flow stops. But when the gate is shut back and put in the fluid flow path, the valve closes completely.

Gate valves Advantages

Gate valves are simple to understand and have a multitude of advantages. Some of these advantages are stated below:

  • Gate valves require very low torque to open and close the valve.
  • Gate valves have very low fluid resistance.
  • The design is simple, and the structure of the valve body is simple.
  • Gate valves can be used on the flow path in both directions. This means that the gate valves are bi-directional and give shut-off in both directions.
  • The working medium does not affect the sealing surface much.
  • Gate valves provide better shut-off features than other valves.
  • There is a very low-pressure drop during operations.
  • Gate valves are affordable compared to other valves like ball valves, even if the quality and size are the same.
  • Gate valves work under both high pressure and high temperature.
  • They are easy to maintain.

Gate valves disadvantages

Gate valves may be advantageous in several areas, but they also have some disadvantages, which may need to be considered. They are as follows:

  • You cannot use gate valves to regulate flow or even throttle it.
  • Some repairs, like grinding and lapping, are hard to do when gate valves are used.
  • Gate valves make noise and vibrate sometimes.
  • These valves are more subject to wear and tear of the seat and disc.
  • The operation is slow. This means that they take longer to open and close as compared to other valves.
  • Large envelope space is needed to install, maintain, and operate gate valves.

5. Check Valves

A unidirectional valve is a check valve. This implies that it only permits the passage of fluids in one direction through it. Check valves should be used in pipelines as they can keep fluids from flowing backward.

The body of a check valve features two openings. One opening is for fluids to join. The second opening is so that you can leave the body with the fluids. They are called two-port valves for this purpose.

The speciality of check valves is that they are self-automated and one of the few valves that do not need to be cycled by a human being. They are receptive to flow and take the media’s aid to open their seat and close it.

It is straightforward to have the working theory of the check valves. The valve allows the fluids to flow in one direction, thus preventing their flow in the opposite direction at the same time. The disk’s interior allows the fluids to flow in the forward direction to cause the valve to open. The valve closes when the flow reverses.

Check Valves Advantages

Check valves are very beneficial. That is why they are used widely and find room in several applications. Some advantages of using check valves are as follows:

  • Control valves prevent the water hammer impact.
  • A low-pressure drop triggered by control valves helps to save electricity.
  • These valves stop chattering.
  • Check valves cause a decrease in downtime.
  • Check valves
  • prevent low output due to valve failure.
  • The risk of valve failure by check valves is significantly reduced.
  • Equipment such as pumps and compressors are secured from damage due to backward flow by control valves.
  • Since they have smaller mobile modules, control valves have low maintenance costs.
  • The footprints are smaller in more recent models of check valves than traditional control valves.
  • Without many modifications and mod mods, check valves can be used interchangeably with swing check valves.

Check Valves Disadvantages

While check valves are very beneficial and have applications in several industries, they also have certain limitations due to which they cannot be used everywhere. These disadvantages are as follows:

Sometimes it becomes difficult to determine whether the valve is closed or open because the moving parts are closed.

  • The internal parts of a check valve cannot be assessed.
  • Check valves have certain limitations on installation configurations.
  • A valve disc can sometimes stay stuck in an open position, and this can cause problems.

 

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