How to make a check valve - Non return valve working principle

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JAES in its catalog offers a wide choice of non-return valve types of the major manufacturers such as:
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RÖTELMANN - Ball valves: https://www.jaescompany.com/catalogo_...
FIP - Diaphragm valve: https://www.jaescompany.com/catalogo_...
KEYSTONE - Butterfly valves: https://www.jaescompany.com/catalogo_...
HAWE – Filling valves: https://www.jaescompany.com/catalogo_...
SCHROEDER VALVES – Relief valves: https://www.jaescompany.com/catalogo_...

The non-return valves or check valves devices are installed on the systems that need to control the fluid’s flow, specifically, to allow fluids to flow only in one direction, avoiding backflow,
which is an unwanted flow of water, in the reverse direction inside the tube.

So, this kind of valve prevents any contamination or dispersion of harmful fluids, in case of reverse fluid circulation.

In this video we will show how easy it is to build a check valve using very simple materials, such as:

14 mm diameter rubber tube
20 mm diameter rubber tube
14 mm diameter rubber seal
A metal sphere of 10 millimeters in diameter
Steel nails
Rubber glue
Abrasive paper

Let's start by saying that there are different types of non-return valves depending on the purpose of their use.

Usually check valves are formed by a shutter, a spring and a gasket.

The operating principle is very simple: as soon as the fluid pumped into the pipe reaches a pressure value that overcomes the force of the spring, the shutter will open, and it will let the fluid to flow through. As higher is the fluid pressure, as bigger the shutter opening will be.

When the pressure value falls below the value that counteracts the force of the spring, the shutter closes, preventing any backflow.

An interesting feature of these valves, is the possibility to set the valve opening with a specific pressure value, to ensure that the fluid reaches users, with a certain pressure value.

The valve we are going to create is a non-return ball valve.

Well. We notice that the 14 mm diameter rubber tube can be inserted inside the 20 mm diameter rubber tube.
Furthermore, the sphere, which represents the shutter of our non-return valve, has a diameter of 10 millimeters, which allows it to slide into the 20 millimeters tube, but not into the 14 millimeters tube.

First, we cut two sections of 6 cm from our 14 mm diameter tube.

Using the abrasive paper we make the ends of the two sections rough.

Now we cut a section from 6 cm in length from our 20 mm diameter tube.

With a piece of rolled abrasive paper we roughen the inner surface of the newly created section.

We get these three sections of pipe.

We take the gasket and we glue it on the end of one of the two 14 mm diameter sections.

While the glue dries, we glue the other 14mm section into the 20mm section, in this way.

Then we put a nail inside the 20 mm section, more or less at this height.

Now we can place the sphere inside the 20 mm tube and we can glue the piece of pipe with the gasket.

This is the result we need to achieve. Our non-return valve is completed and is ready to be tested.

For the test, we inserted our valve into the end of the remaining 20 mm rubber tube
and we inserted a funnel into the other end, created by cutting the neck of a plastic bottle.

By inserting the valve in this way and by letting the water flows inside the tube, we notice that the water, flowing through our check valve, has a high pressure outlet.

This is because the water flowing inside the tube at a certain pressure, entering the valve, pushes the sphere against the nail. Due to this obstacle, represented by the sphere, the water flows outside our valve at higher pressure.

If we try to insert the valve in the opposite direction, we notice instead that only a small amount of water is coming out the pipe. In fact, most of it, remains inside the pipe.

This is because the water falling into the pipe, entering the valve pushes the sphere against the outlet tube. The sphere and the gasket of the tube create a sort of shutter that prevents the water from flowing out the valve.