Non-slam check valves are check valves used to prevent reverse fluid flow. Also, these valves are meant to eliminate or reduce water hammer and their associated effects. A water hammer is a high-pressure shock wave that happens when the fluid flow stops abruptly because of a pump or valve closing quickly in a piping system. When water hammer happens, the fluid flow reversal causes high stress on the piping system which endangers its structural integrity and may cause damage or rupture. Non-slam check valves are used to prevent water hammers and ensure fluid flows in one direction only. Non slam check valve manufacturer produce this valve without handle or actuator but it works mechanically to stop the fluid flow from reversing.
This type of valve uses pressure difference to close and open fluid flow. When the pressure is low, the valve disc closes automatically. When the inlet pressure is high, the disc opens fluid flow. This type of valve is very important in not only preventing water hammers but also preventing damage to the piping system such as pumps and boilers due to reverse flow. In addition, this valve prevents fluid contamination such as in fresh water applications.
How does a non-slam check valve work?
A non slam check valve works based on differential pressure. When the upstream pressure is high, it provides enough pressure energy that is used to open the valve disc. The disc is supported by the use of a spring. As such, the pressure energy compresses the disc to open. When the disc opens, fluid flows through the valve from the inlet to the outlet port and finally to the piping system. The valve closes when fluid pressure reduces.
The fluid pressure reduces for example, when the pump is closed. As such, fluid attempts to reverse flow direction because upstream pressure is lower than the downstream pressure. In the instance the fluid attempts to reverse, the valve disc closes immediately due to the low-pressure drop.
Types of non-slam check valve
1. Metallic seated non-slam check valve
This is a non-slam check valve that is meant for use in high-pressure and high-temperature applications. This type of check valve has its seat made of metallic materials such as carbon steel, stainless steel, ductile iron, brass, and bronze among other materials. These materials are used to make which makes it suitable for high temperature applications. In addition, metallic seats have high strength which helps to enhance high strength against high pressure. Such valves are resistant to corrosive products.
2. Soft-seated non-slam check valve
This is a check valve in which the seat is made of soft materials such as rubber or plastic. However, the valve body is made of strong metallic materials to ensure the valve is strong against high pressure and impact damage. These materials have low melting temperatures and thus are recommended for use in temperatures below 60oC. These materials have low strength and thus they can work well in medium and low-pressure applications. Also, soft seated non-slam check valves are used in corrosive applications because they are highly resistant to corrosion relative to their metallic seated counterparts.
Applications of non-slam check valves
- Non-slam check valves are used in chemical industries.
- These valves are used in the foods and beverages industries.
- They are used in pharmaceutical applications.
- These valves are used to prevent the backflow of water or steam in boiler applications.
- They are used to prevent water contamination in the freshwater supply.
- These valves are used in the oil and gas industries.
- They are used in wastewater treatment.
Advantages of non-slam check valves
- Non-slam check valves prevent water hammers from occurring.
- These valves have a low-pressure drop.
- These valves can maintain the required fluid pressure.
- They do not allow reverse fluid flow.
- These valves can be installed in vertical or horizontal orientation.
- They are automatic valves.
- These valves are cheaper relative to other valves.
- They are versatile and durable.
Disadvantages of non-slam check valves
- Non-slam check valves allow fluid flow in one direction only.
- These valves cannot be inspected while in operation.