Non return valves, also known as check valves or NRVs, are essential components in various industries and systems. Their primary function is to enable fluid flow in one direction only, preventing backflow and ensuring the smooth operation of equipment. While all NRVs serve the same purpose, there are different types available, each designed to suit specific applications and operating conditions. In this comprehensive guide, we will explore six of the most popular types of non return valves, their features, and their uses.
What is Non Return Valve or NRV Check Valve?
Non return valves, or NRVs, are like traffic directors for liquids. They make sure the flow goes in one direction only, a bit like one-way streets. They have two openings: one for things to come in and the other for things to go out. These valves do their job without needing someone to turn them on or off manually. They’re pretty smart and work all by themselves, no handles are needed!
The Main Types of Non Return Valve or NRV Check Valve
1. Lift Check Valve
The lift check valve is commonly used in high-pressure systems and situations where the flow velocity is significant. It features a piston disc guided by long contact points, ensuring precise movement and alignment. To prevent sticking and ensure smooth operation, lift check valves are equipped with steam jackets that regulate temperature and expansion. This type of NRV resembles a globe valve in seat design, with the disk positioned inside a ball or piston. Ball-lift checks are often employed in high-velocity fluid services, offering superior leak-tightness compared to other types of check valves.
Key Features: Works well with high pressure, keeps things moving fast, and has a sturdy build.
- Pros: Good for high pressure and fast flows. Strong and sticks less.
- Cons: Might need more space and can be a bit heavy.
2. Swing Check Valve
The swing check valve is an unguided disc-type valve that operates based on the movement of the disc. It is widely used in various industries and applications, offering versatility and reliability. Swing check valves can be equipped with different disc and seat designs to suit specific requirements. Soft-seated swing check valves provide excellent leak-tightness, especially when combined with a metal seat ring and resilient insert. The seating angle, which determines the disc movement, can range from 0 to 45 degrees. Larger seat angles limit disc movement, resulting in quicker closure and reduced noise levels.
Key Features: Swings fully open or closed, can be quieter with softer seats, but might stick sometimes.
- Pros: Opens and closes fully, less noisy with soft seats.
- Cons: Can get stuck, might not seal perfectly.
3. Folding Disc Check Valve
Folding disc check valves, also known as double-disc or split disc check valves, are designed with a wafer-body pattern, making them compact and lightweight. These valves are commonly used in low-pressure liquid and gas field services. The folding disc design provides convenient installation and maintenance, making them a popular choice where space constraints are a concern. They are known for their reliable operation and excellent sealing capabilities, ensuring efficient flow control and preventing backflow.
Key Features: Small and light, fits nicely in tight spaces, but not the best for really high pressure.
- Pros: Lightweight and compact, great for small spaces.
- Cons: Not ideal for high-pressure situations.
4. Tilting Disc Check Valve
The tilting disc check valve addresses some of the limitations of the swing check valve by offering improved performance and functionality. This type of NRV is specifically designed to allow complete opening and stable operation, even at low flow velocities. The disc of a tilting disc check valve floats within the flow, with fluid passing over its top and bottom surfaces. The dome-shaped disc minimizes the impact on the dashpot, allowing for prolonged lift and reduced flow-induced dynamic stresses. Tilting disc check valves are ideal for turbulent, pulsating, and high-speed flows, offering enhanced reliability and durability.
Key Features: Opens all the way, and handles different flow speeds, but might not be as stable with slow flows.
- Pros: Opens fully, and works well with different flows.
- Cons: Might not be as stable with slow flows.
5. Stop Check Valve
Stop check valves serve a dual purpose, acting both as a check valve and as an isolation (stop) valve. They can be used to regulate flow in one direction and completely shut off flow in both directions, regardless of pressure differentials. Stop check valves are commonly employed in applications where precise control and isolation are required. They come in various designs, including Wye-pattern, angle-pattern, tee-pattern, and inclined pattern, catering to different system configurations. Swing-and-piston lift-disc style check valves are typically used in stop check valve applications, ensuring reliable and efficient operation.
Key Features: Does double duty as a regular check valve or can completely stop flow, versatile but may need more understanding to use.
- Pros: Versatile, can work as a regular check valve or completely stop flow.
- Cons: Might be more complex to use.
6. Vertical or In-Line Check Valve
Vertical or in-line check valves are versatile valves used in both horizontal and vertical piping systems. In horizontal lines, in-line ball check valves are commonly employed, ensuring efficient flow control and preventing backflow. These valves often feature a spring-assisted closure mechanism, providing faster closure and minimizing flow reversal. In vertical lines, spring-assist closure may or may not be present, depending on the specific requirements of the system. Vertical or in-line check valves are compact in size, making them suitable for applications with limited space.
Key Features: Compact, good for small spaces, closes quickly using a spring but might need extra help in some positions.
- Pros: Compact, good for small areas, use a spring for quicker closure.
- Cons: Might need extra help for certain positions, like in horizontal lines.
Pros and Cons of Non Return Valve | Check Valve, NRV Valve, Nrv Check Valve
|Advantages of Non-Return Valves
|Prevents the reverse flow of fluids, maintaining directional flow
|Prevents reverse flow of fluids, maintaining directional flow
|Potential for clogging due to debris or contaminants
|Reduces water hammer effects in piping systems
|Higher pressure drop compared to straight-through valves
|Helps maintain system efficiency by preventing backflow
|Limited suitability for handling slurries or viscous fluids
|Offers protection to pumps and other equipment from damage
|Possible issues with sealing and leakage over time
|Available in various designs suitable for different applications
|Higher initial cost compared to some simpler valve types
Why Use Different Types of Non Return Valves?
The use of different types of non return valves is crucial for ensuring optimal performance and efficiency in various systems and applications. Each type of NRV is designed to address specific challenges and requirements, providing unique benefits and features. By selecting the appropriate type of NRV, system designers and operators can prevent backflow, protect equipment from damage, and minimize downtime. Additionally, the use of NRVs can save energy, reduce valve failure rates, and lower maintenance costs.
Summary Of The types of non return valve and NRV check valve
non return valves play a vital role in maintaining the integrity and efficiency of fluid systems. Understanding the different types of NRVs available and their respective applications is essential for selecting the right valve for a given system. Whether it’s a lift check valve, swing check valve, folding disc check valve, tilting disc check valve, stop check valve or vertical or in-line check valve, each type offers unique advantages and characteristics. By utilizing the appropriate type of non return valve, system operators can ensure reliable and efficient fluid flow in their applications.