Spring Check Valves

SPRING CHECK VALVES

Spring check valves are also known as one-way valves or non-return valves. The spring check valves are a check valve that allows the flow of fluids in a single direction only. Spring check valves are designed as two-port valves, that is, two openings in a single valve. One of the openings is for the inflow of fluids while the other is an outlet for fluids.

Spring check valves help avoid reverse flow through a spring that closes the valve when the need arises. Spring check valves are made of stainless steel SS316 materials and have a maximum working pressure of 1000 PSI. The available sizes of the valve range from 1/4” to 2”.

Material Specification	Stainless steel SS316
Connection Type	NPT and BSPP
Size	1/4” to 2”
Working Pressure	1000 PSI

1. What are Spring Check Valves?

Check valves are valve types that allow the flow of fluids in one direction. Check valves are used to prevent the backflow of fluids in pipelines installation. The flow of fluid in check valves moves from a high level to a low level. When the high pressure in the inlet end is more than the cracking pressure, fluid flow begins through the check valve by overwhelming the spring strength. Check valves have high reliability and durability. More so, they can be installed and operated easily.

Check valves are designed with two sealing types with soft seats and metal seats.

Soft seats: soft seats in valves are commonly made from Viton or PTFE which are thermoplastic materials. They are suitable to be applied in installations involving chemicals to ensure tight sealing. The sealing it gives is very reliable, however, for dirty fluids or strong abrasives, soft seats are not recommended for use.
Metal Seats: a metal seat is stronger than soft seats as it can endure strong abrasive fluids, high temperature, working pressure, and hydraulic shock. The temperature level of metal seats can withstand is 537⁰C (1000⁰F). It can also withstand exposure to high corrosion and erosion, however, the sealing it gives is not 100% for metal to metal connection.

Spring Check Valve BSPP SS316

Spring check valves are a type of check valves that performs the major function of check valves. Spring check valves are installed in systems to help prevent the backflow of fluids. They are applied in a variety of industries and have a high durability level. Spring check valves are available in sizes ranging from 1/4 inches to 2 inches and can withstand a working pressure of 1000 PSI.

2. What materials are the Spring Check Valves made of?

The materials of Spring check valves are stainless steel SS316 material. The stainless steel material contains other carbon, chromium, nitrogen, aluminum, copper, selenium, molybdenum, nickel, titanium, etc. Stainless steel contains a minimum of 11% chromium, giving it a high resistance for corrosion and strength. Stainless steel valves are preferred due to this benefit.

The table below shows the material for the components of the spring check valves:

No.	Part Name	Material
1	Cap	CF8M & SS316
2	Body	CF8M & SS316
3	Seat Ring (O-Ring)	VITON
4	Seal Gasket	PTFE
5	Disc	CF8M & SS316
6	Spring	SS316

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3. How does a Spring Check Valve work?

Cracking pressure is defined as the minimum upstream inlet pressure that a closed valve needs to open up and start fluid flow. The inlet pressure must attain the cracking pressure, and this opens the inner spring of the valve to allow fluid flow in one direction while blocking the other channel to prevent backflow. The standard cracking pressure for valves is 0.5, 1.0, or 2.0 bars. This value varies and depends on the manufacturer’s preference during production. Also, the specification for cracking pressure can be requested for, it will be available.

Spring Check Valve 2 Pieces Body

Some technical specifications for spring check valves production are as follows:

Specified materials to enable chemical compatibility
End connection types
Pressure drop level for the valve when it is opening and operating
Amount of time taken for the valve closure
Minimum cracking pressure to allow full opening of the valve.

When the inlet pressure drops beyond the cracking pressure value, the spring pushes the disc with force to close the orifice. One main drawback of the spring check valve is the maintenance method. During maintenance, the valve must be completely detached from the system before it can be worked on.

4. Can a Spring Check Valve be installed horizontally?

Spring check valves are designed to allow vertical or horizontal installation, however, a condition has to be met before installation. Whichever way the valve has to be installed, the flow needs to run in an upward direction. The spring check valve body has a stamp showing the flow direction to enable easy installation in the right position.

The vertical installation of the spring check valve requires some expert knowledge. Here are some of the major selection criteria for spring check valves:

Material: The material used in the spring check valve has to be compatible with the system process fluids and strong enough to withstand the fluid's characteristics.
Design type: The design used is based on the type of application intended. Therefore, you have to select the best suitable for the application.
Connection: The connection type is also critical as it determines the sealing tightness to avoid leakages.
Size: The size of the valve will determine the pressure level and flow rate of fluids. The right size must be selected to increase efficiency and avoid disruption of flow.

Spring Check Valve BSPP SS316

5. What is the difference between a Spring Check Valve and a Swing Check Valve?

Swing check valves are mostly applied in the industry. Both spring check valves and swing check valves perform the same direct flow function in one direction and prevent reverse flow. However, there are some differences between them, these are discussed below:

The first difference is in the device for operation. In spring check valves, spring is the operator, while a swing check valve uses a disc. The swing check valve has a disc connected to a hinge that swings from the seat to enable the fluid flow in a forward direction. Unlike the spring check valve that remains closed when there is current flow in the direction and when the valve is closed, a spring takes up the action.
Another difference is the installation methods. Swing check valves are limited in the installation method as they can only function when installed for horizontal flow applications. However, spring check valves can be installed in horizontal or vertical directions. Therefore, spring check valves are more flexible and versatile in application, plus, they can be used with special direction pipes.
Also, spring check valves have a reduced slam and water hammer effect than the swing check valves. Spring check valves have a spring that accommodates the weight and helps the poppet reduce the slam and water hammering when closing. Due to this, spring check valves are referred to as silent check valves. This feature is not available for the swing check valve, and it can exacerbate the rate of slamming in the system. In other words, swing check valves are closed when there’s a backflow while the spring check valve closes by default.