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How does a ball valve work?

Valves are shut-off or regulating equipment placed along the path of fluid streams.

In this video we will show you how a ball valve works. Moreover, if you watch the other videos on our playlist you will find out all the other types of valves existing.

JAES, for over a decade has been providing its customer with the best solutions for their supply chain and in their catalogue you can find any kind of valve from the leading manufacturers.

The ball valve is one of the most common valves, mostly used in domestic faucets, or in pipes for water distribution, and takes its name from the shape of the shutter and by how it moves. It is indeed shaped like a ball: to obstruct the flowing, the floating ball makes a 90° rotation on the normal axis to that of the piping run.
Let’s now see together how a ball valve is made of:
1. Firstly we find the valve body, and we can clearly identify two housings at both ends which will be coupled to the pipes.
2. On the inside we can find the floating ball, a drilled sphere which enables the fluid to flow through. It is made of brass for valves that have to work with low pressures, while in carbon steel for high pressures. Some models, instead, may be made of synthetic material such as PVC for working with non-corrosive or colder fluids.
3. The seal, directly connected to the shutter, allows the correct tightening of the valve, so that there aren’t any leaks of fluid. It consists of two rings in plastic material like Teflon.
4. Above the shutter we find the stem, which connects the floating ball to the lever used to operate the valve.
5. The lever handle is usually made of cast or molded aluminum for smaller valves, while in durable anti-corrosive steel for bigger valves.

The operation of the ball valve is very simple, let’s now see it in detail.

The valve is installed in the middle of 2 pipes, keep in mind that this is not a control valve but rather a shut-off valve, that is, it interrupts the fluid that flows inside it. To open or close the valve, the lever handle at the top must be operated, and just a ¼ turn is enough to operate it, since the floating ball has to rotate by only 90 °.

One possible disadvantage of the globe valve includes the water hammer: it is a shockwave created by the inertia of a liquid column in motion that crashes against a wall. When we close a globe valve, the liquid flow stops so quickly that the shockwave can cause damages to the nearby pipes.
Let’s now move onto the different globe valves available on the market. We can find 2 main types:
1. Full-bore valve, in which the hole of the shutter has the same dimeter of the pipe.
2. Reduced-bore valve, in which the hole of the shutter is smaller compared to the pipe’s diameter. This type of valve reduces the speed of the fluid flowing internally.

We also find a third type of ball valve called Venturi valve, used to increase fluid pressure.
It is named after the physicist Giovanni Battista Venturi, who discovered the relationship between pressure and speed in the physics of fluids.
The valve with the Venturi tube looks like a normal ball valve, the only difference is found in the central diameter: the smaller diameter causes the liquid to increase its speed and once it reaches the larger section, the fluid will increase its pressure while losing speed. This type of valve is used in filling stations or in steam plants, where high pressure is required.

The Venturi effect is called “hydrodynamic paradox” because it is believed that pressure will increase in more constricted areas of the pipeline while thanks to the flow rate law, we observe the exact opposite is taking place.
Ball valves have several advantages:
• they allow the full flow port, minimizing load dispersions and pressure drops.
• they are cheaper compared to many other types of valves
• they close quickly with a simple operation
• they do not require any type of maintenance and lubrication
They also have some disadvantages:
• The water hammer, already mentioned above, is present in all types of fast closing valves
• When used to regulate the flow of the fluid it can create turbulence; this would lead to a reduction in flow rate, more noise and vibrations that could damage the valve itself and the pipes connected to it.

Do you know how many types of valves we use every day? Don’t miss the videos of our playlist, you will find out all kinds of valves that surround us.
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