There are different kinds of check valves. These are some of the valves that the non return valve manufacturers manufacture:
- The swing check valve has a disc which is pivoted on the hinges or trunnion. The mechanism is simple, and the forward pressure pushes the hinge upwards which means there is flow and the valve shuts down due to the self weight or when the cracking pressure is not sufficient.
- The loft check valve is one which has a disc which is seated on an exit. When the pressure from the fluid is present the valve remains shut. When the disc is released by mechanically lifting it off the exit hole, then the fluid escapes and the valve once again shuts down.
- A ball check valve has a ball often inside a conical section with a spring to keep it in place. When the ball is in place there is no flow and when the ball is lifted the flow occurs. The spring is kept to maintain the pressure and to keep the ball in position.
The diaphragm non return check valve has a rubber diaphragm which responds to the flow of the fluid. When there is sufficient pressure the diaphragm depresses and the valve is open. When the pressure lets off, the diaphragm shuts up again and the valve is closed.
A stop check valve is one which overrides the entire flow criterion and shuts down the system. This is done when there is a need for manual over ride of the system.
If one is interested in finding the best manufacturers of valves one needs to have an idea about them. Let us take a look at some of the manufacturers.
The western countries non return valve manufacturers are:
- Proflow Instrumentation Systems Inc Toronto makes all types of valves. Foot valves, flap valves, Plastic check valves, Brass check valves, high pressure check valves, diverter valves, cartridge check valves, stainless steel check valves, swing check valves and much more.
- Maxpro Technologies Inc, Fairview manufacture high quality check valves used for direction control and for complete shut off. Ball check valves which are used as a reverse flow check valve are recommended when the tight shut off is necessary. The designs of these kinds of check valves has a floating poppet design which ensures that there is full flow about the ball and this minimizes pressure drop.
- DaPro Rubber Inc based in Tulsa is on e of the leading manufacturers of molded plastic and rubber custom non-metallic valves. One could order the number of valves one wants and once they are given eh specifications the order is executed.
- Dwyer Instruments Inc in Michigan City is another leader in this sector. They are in to all kinds of instrumentation make controls for various kinds of purposes. They serve the oil and gas, chemical and other major markets.
Some the eastern countries non return valve manufacturers are mostly located in China :
- Wenzhou Zhengyu Light Industry Machinery Co Ltd
- Zhejiang Donjoy Valve Pipe Fitting Co Ltd makes sanitary non return check valves
- Laizhou Dongsheng Valve Co Ltd make stainless steel non return valve
- Beijing Sihai Xiangyun Plastic Parts Co Ltd makes plastic non return valves.