Industrial valves have various types, and they are used in many industries for multiple purposes. Industrial valves used in the power industry are designed to increase power generation efficiency and maximize power performance. However, valves in power plants may seem like just a tiny and simple fraction of the vast power station; in reality, they have a pivotal role in power plants. Even a single power plant has many types of valves, and each of them has different roles.
The basic principle of design behind most valves is almost the same; the only difference is in their manufacturing techniques and materials. Nowadays, manufacturing techniques have significantly improved, resulting in valves’ more sophisticated and efficient operation. In this article, we will look at the common types of valves used in the power industry and their significance.
Classification of Valves used in Power Industry
Each type of valve has its own significance and use in the power industry. They are used according to the requirements of flow control. Depending upon the type of process happening in each pipeline, the industrial valve in each pipeline also varies. For example, in the case of high integrity slurries, valves should have tight shut-off. The slurries are usually corrosive and abrasive, so the disc in the valve should be easily replaceable. For the body, the ideal material is iron. Below we have classified valves used in the power industry.
Valves for Isolation Purposes
Valves for isolation services are the ones that stop the flow of media when needed. Following valves fall in this category:
- Bonnet Gate Valve
The Bonnet gate valve should be made of cast iron, and its seat rings should be welded to avoid leakage.
- Pressure Seal Gate Valve
Pressure seal gate valves have two designs, wedge and parallel. Both of them should be hard-faced and have self-cleaning abilities.
- Pressure Seal Globe Valve
In pressure seal globe valves, the disc, seat rings, and the backseat should be hard-faced to stand high pressure for a long time.
- Bolted Bonnet Globe Valve
These globe valves are designed to provide throttling services. Thus it should be thicker to withstand more stress. In addition, its seat ring must be welded to prevent leakage.
Valves for Flow Reversal Protection
Valves in the flow reversal protection category should be able to protect the counter flow. The valves of this category have hard seated surfaces and anti-corrosive nature. They also have large diameter hinge pins to absorb the movement of the media. Following valves fall in this category:
- Bolted bonnet swing check valve
- Pressure seal check valve
- Nozzle check valve
- Dual plate check valve
Valves for Special Applications
There are some valves for special applications. The application depends upon the type of energy resource and needs of the power plant. Here is the list of valves for special applications:
- Triple offset butterfly valve
- High-performance butterfly valve
- Double eccentric butterfly valve
- Metal-seated ball valve
- Resilient-seated concentric butterfly valve
Most Commonly used Industrial Valves in Power Industry
Here is the list of industrial valves used in the power industry:
1. Bolted Bonnet and Pressure Seal Gate Valves
As the name suggests, gate valves have a disc or wedge that acts as a gate to block or allow the flow path of media. Gate valves are not made for throttling. Instead, their main role is the isolation of media without much restriction. If you want to take the best from gate valves, only utilize them as fully opened or fully closed.
There are two kinds of valves in the isolation valves category: gate valves and globe valves. They are designed to stop the flow of media in an emergency or when there is a need for pipeline maintenance. These valves can also be used to connect the media to external process equipment. They can also direct the media to a certain path.
The bolted bonnet valves are designed; it has a straight-through port design to minimize erosion, friction, and pressure drop. In the case of pressure seal gate valves, there are two available designs for high pressure and high-temperature applications: the parallel disc and flexible wedge.
Bolted bonnet valves are sturdy and usable in high temperatures, but these valves can leak when the pressure becomes high. So for high-pressure applications higher than 500 psi, you should use pressure seal valves because their seal increase as the pressure increase. Applications that are below ANSI Class 600 can use bolted bonnet gate valves.
2. Bolted Bonnet and Pressure Seal Globe Valves
Globe valves have almost similar designs as gate valves; the only difference is the disc. Globe valve has globe-like disc while gate valve has wedge-shaped disc. Globe valves can be used for shut-off, turn-on, and throttling purposes. These valves are considered ideal for the throttling of media. The drawback of globe valves is that they cannot be used in media with high flow rates.
In the power industry, globe valves can effectively control flow. Moreover, the plus point of globe valves is that they have a simple design, so it’s easier to maintain and clean them as compared to other valves. Its simple design also creates less friction that enhances the service life of the valve.
Some things you should save in mind while choosing the globe valve for the power industry is the type of medium, the flow rate of media, and the amount of control needed. You should also look for the seat, disc, and the number of turns to open or close the valve.
Just like the bolted bonnet gate valve, bolted bonnet globe valve can also be used in high temperatures, but it is not suitable for pressure higher than 500 psi. Use pressure seal valves if the media has high internal pressure.
3. Bolted Bonnet Swing Check or Pressure Seal Tilt Disc Check Valves
Check valves are used when the unidirectional flow of media is needed. They are anti-backflow valves. Check valves have 45 degrees angled disc design to reduce water hammering. It can also adapt to high-velocity media. The disc design also allows low-pressure drop. In the power industry, check valves protect the pipeline and various equipment from the damage caused by reversal flow. Check valves take the most damage out of all the valves because they are often exposed to media and various operational challenges. The downside of the check valve is water hammering, jamming, and wedging. So you should carefully choose the check valve design. If you are looking for a cost-effective check valve, then opt for the bolted bonnet and pressure seal tilt disc valve. The tilt disc design also seals more tightly than the other check valve designs. Maintenance of tilt disc valve is also easy because of its simple design.
4. Dual Check Valves
Dual check valves are also the type of check valves. They are considered more reliable, durable, efficient, and lightweight than swing check valves. The dual check valve has various springs in order to increase the valve response time. In the power industry, dual check valves are used where sudden changes in media flow are expected. They adapt well to the sudden changes in media flow. Due to this characteristic, the risk of water hammer is also lesser in this design.
5. Nozzle Check Valves
Nozzle check valves, also known as silent check valves, is a special kind of check valve. It is designed to provide a quick response against media backflow. So if in the power plant, there is a high risk of backflow, use this valve. The design of the nozzle check valve also minimizes the water hammering and vibrations caused by the media. Nozzle check valves can also provide a quick response to shutoffs.
Always consider the velocity of flow media while choosing the nozzle check valve. Because, although high velocity is not needed to close the valve, the valve will be immediately closed if there is an excellent reduction in the velocity of media flow. This action is essential to reduce water hammering. The major advantage of the nozzle check valve is that they are customizable according to the requirements of the power plant. You can customize it to fit the application irrespective of the size of the pipeline.
Ball valve belongs to the quarter-turn family. Ball valves, as the name suggests, have a ball-like structure that turns 90 degrees to open or close the valve. They act as a stopper in the power industry. Metal seated ball valves are more commonly used in the power industry because they can withstand high temperatures and pressure. The metal seated ball valve can withstand a temperature of over 10000F. These valves are also more resilient and less prone to wear. Metal seated ball valves also provide better shutoff capabilities because of the bi-directional metal to metal sealing. These valves are cost-effective, can withstand high temperatures, and they are also fire resistant.
7. High-Performance Butterfly Valve
Butterfly valves have a thin disc and wafer-like body. The disc rotates bi-directionally. These valves are lightweight, easy to install, repair and maintain. High-performance butterfly valves (also known as HBPV) has two offsets instead of one. The reason for the two offsets is to create better-sealing capability and produce less friction. Due to less friction, these valves have a longer service life.
HBPV are used in water intake appliances, cooling water systems, and industrial wastewater applications. If the seat is made up of metal, this valve can withstand high pressure and temperature.
8. Resilient-Seated Concentric Butterfly Valves
Resilient seated concentric butterfly valves have a seat made up of high-grade rubber. They are used in low pressure, low temperature, and less severe power plant applications. It can effectively close the valve in low-pressure appliances because of the rubber seat. The resilient seated butterfly valve is cost-effective, and its maintenance and installation are also easy.
9. Triple Offset Butterfly Valves
The triple offset butterfly valves have three offsets, an additional offset not commonly found in other butterfly valves, placed in the seat. The third offset is placed to reduce friction during the opening and closing of the valve. Triple offset butterfly valve also allows gas tightness and bi-directional flow. This valve is considered best when top considerations are high pressure and temperature. Moreover, the triple offset butterfly valve offers the best sealing and longer service life among all the types of butterfly valves available in the market.
Industrial valves used in the power industry have to undergo intense pressure and extreme temperature. So picking the right valve is essential to running the power plant smoothly. Read our above guide to know which valve is suitable under given circumstances.