Check Valves: Types, selection, and uses

• Check valves are an essential component in fluid and gas systems, ensuring that the flow moves in only one direction and preventing backflow.

Types Of Check Valves:

There are several types of check valves, each with its own unique design and operating principle. Some of the most common check valve types include:

• Swing Check Valve
• Wafer Check Valves
• Tilting Disc Check Valves
• Lift Check Valves
• Foot Check Valves
• Pneumatic Check Valves

1). Swing Check Valves:

• Swing check valves are among the most commonly used types of check valves. They feature a simple design comprising a disc that swings open in one direction to allow fluid or gas flow and closes in the opposite direction to prevent backflow.

• Swing check valves are popular due to their reliability and low maintenance requirements. They are also highly versatile and can be used in a variety of applications, including water treatment plants, industrial piping systems, and even fire protection systems.

• One of the key benefits of swing check valves is their ability to handle high flow rates. They can also be used in horizontal or vertical piping systems, making them ideal for a broad range of applications.

• When it comes to choosing a swing check valve, it's important to consider factors such as the flow rate and pressure of the system, as well as the materials of construction. For instance, swing check valves made from PVC may be suitable for water treatment plants, while those made from cast iron may be more appropriate for industrial applications.

2). Wafer Check Valves:

• Wafer check valves are a popular type of check valve used in various applications, especially those that involve liquids. These compact and lightweight valves are designed to prevent backflow and keep the flow going in one direction.

• One of the key advantages of wafer check valves is their simple design, which makes them easy to install and maintain. They are also much more affordable compared to other types of check valves, making them a popular choice for budget-conscious buyers.

• Wafer check valves work by using a thin disc or plate that opens and closes with the flow of fluid. When the fluid flows in the forward direction, the valve remains open, allowing the liquid to pass through. When the flow reverses, the disc is forced to close, preventing the fluid from flowing backward.

3). Tilting Disc Check Valves:

• Tilting disc check valves are a popular type of check valve that is commonly used in high-pressure systems where reliability and safety are paramount. These valves are designed to prevent backflow and ensure that fluid or gas flows in only one direction.

• The valve is made up of a disc that tilts or pivots to allow the fluid or gas to flow in one direction. When the flow reverses, the disc closes and seals the valve, preventing backflow. This design makes tilting disc check valves ideal for high-pressure applications, as they are less likely to open due to pressure changes.

• There are several advantages to using tilting disc check valves, including their ability to operate in high-pressure and high-temperature environments. They also offer low head loss and are less likely to trap debris compared to other types of check valves.

• However, there are some limitations to consider. Tilting disc check valves can be more expensive than other types of check valves, and they are not suitable for low-pressure applications. Additionally, the valve may experience wear and tear over time due to the constant pivoting motion of the disc.

4). Lift Check Valves:

How do Lift Check Valves Work?

• Lift check valves use a guided disc that moves up and down to control the flow of fluids or gases. When the fluid or gas flows in the correct direction, the valve's disc lifts, allowing the flow to continue. If the flow reverses, the disc drops back onto the seat, closing the valve and preventing backflow.

• The disc's weight or a spring typically holds the valve's disc in the closed position. When the flow reverses, the pressure difference causes the disc to lift, allowing flow in the opposite direction. Lift check valves are suitable for a wide range of applications and offer several advantages over other check valve types.

5). Foot Check Valves:

• Foot check valves, also known as bottom valves, are commonly used in vertical pipe installations and submerged applications. These valves are designed to prevent backflow in a pipeline by using gravity to maintain a seal.

• Foot check valves are typically made of stainless steel, brass, or bronze and are available in various sizes and pressure ratings. The valve body houses a check valve mechanism that allows flow in one direction and prevents flow in the opposite direction.

• The primary advantage of foot check valves is their ability to operate automatically without external power or control. They are suitable for applications where continuous flow is required and where the discharge pipe is submerged in liquid.

• The valve's name is derived from its position at the bottom of the discharge pipe, where it rests on the bottom of the tank or sump and is designed to maintain a seal against the pressure of the liquid above it. Foot check valves are commonly used in water wells, irrigation systems, and sewage pumping stations.

• Foot check valves may require periodic maintenance to ensure that they are functioning correctly. This may involve cleaning the valve and its components or replacing any worn or damaged parts. Proper maintenance helps to ensure a long service life for the valve while preventing leaks or other issues that may result in downtime or loss of productivity.

6). Pneumatic Check Valves:

Pneumatic check valves are specialized valves that allow fluid to flow in one direction only and prevent backflow. These valves come in several different types, each with their own unique advantages and disadvantages.

A). Ball Check Valves:

• One type of pneumatic check valve is the ball check valve. Ball check valves use a ball or sphere to stop the flow of fluid in the opposite direction. When the pressure in front of the ball is greater than the pressure behind it, the ball is pushed against the seat and seals the valve. When the pressure behind the ball is greater than the pressure in front of it, the ball moves away from the seat and allows the fluid to flow through the valve in the opposite direction.

B). Diaphragm Check Valves:

• Another type of pneumatic check valve is the diaphragm check valve. Diaphragm check valves use a flexible rubber diaphragm to stop the flow of fluid in the opposite direction. The diaphragm is held in place by a spring, which keeps the valve closed until the pressure on the inlet side of the valve exceeds the pressure on the outlet side of the valve. When this happens, the diaphragm is pushed aside and the fluid is allowed to flow through the valve in the opposite direction.

Selecting the Appropriate Check Valve for Your Use:

• When it comes to selecting the appropriate check valve for your specific needs, there are several factors to consider. These factors include the type of fluid or gas being transported, operating conditions such as flow rates and pressure ratings, and the material of construction.

• First and foremost, it's crucial to choose a check valve that is compatible with the fluid or gas being transported. Different check valve types are designed to handle various fluids and gases, so it's essential to choose the correct check valve for your application.

• Next, consider the operating conditions. Factors such as flow rates, pressure ratings, and temperature range can all impact the performance of a check valve. Be sure to select a check valve that is suitable for the specific flow conditions in your system, as well as the maximum and minimum pressure requirements.

• The material of construction is another critical factor to consider when selecting a check valve. Different materials offer varying levels of chemical and corrosion resistance, and some materials may be better suited for specific applications. For example, stainless steel check valves are commonly used in the food and beverage industry, while PVC check valves may be suitable for certain water treatment applications.

Where Are Check Valves Used?

Check valves find applications in various industries and scenarios, including:

Industry/Sector	Application/Use
Plumbing	Preventing backflow in water and sewage systems
Oil and Gas	Maintaining the directional flow of fluids in pipelines and drilling operations
Chemical Processing	Preventing contamination in chemical transfer lines and processing systems
Water Treatment	Preventing contaminated water from reversing flow into clean water systems

Advantages and Disadvantages of Check Valves:

A). Advantages of Check Valves:

Check valves offer various advantages, such as:

• Preventing fluid contamination: Check valves help maintain a clean and uncontaminated flow of fluids by preventing backflow.
• Reducing pressure surges: Check valves reduce pressure surges that could occur if fluids or gases are forced to flow in the opposite direction.
• Improving system efficiency: Check valves help maintain the efficiency of a system by ensuring a steady flow of fluids or gases in one direction.
• Saving space: Check valves come in various compact designs that allow for easy installation in tight spaces.
• Reducing maintenance: Check valves are relatively low maintenance and can last for a long time if the right type is selected for the application.

Disadvantages of Check Valves:

Check valves also have some limitations, such as:

Disadvantages	Explanation
Pressure drop:	Check valves can cause a significant pressure drop, which can impact system efficiency.
Restrictions on flow rate:	Some types of check valves may restrict the flow rate of fluids or gases, which can impact system performance.
Incompatible with certain fluids:	Check valves may not be compatible with certain fluids, such as highly viscous or corrosive liquids, which can affect their lifespan and performance.
Noisy operation:	Some types of check valves can be noisy during operation due to the flow of fluids or gases being disrupted and redirected.