How does a Ball Valve work? Hydraulic valves - Water Hammer - Venturi

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Valves are shut-off or regulating equipment placed alongthe path offluid streams.In this video we will showyouhow a ballvalve works. Moreover, if you watchthe other videos on our playlist you will find out all the other types of valvesexisting.JAES, for over a decade has been providing its customer with the best solutions for their supply chain and in theircatalogue you can find anykind of valve from the leadingmanufacturers.The ballvalve is one of the most common valves, mostly used in domestic faucets, or in pipesfor water distribution, and takes its name from the shape of the shutterand by how it moves. It is indeed shaped like a ball:to obstruct the flowing, the floating ballmakesa 90° rotation on the normal axis to that of the piping run.Let’s now see together how a ballvalve is made of:1.Firstly we find the valve body, and we can clearly identifytwohousings at both ends which will becoupledto the pipes.2.On the inside we can find the floating ball,a drilled spherewhich enables the fluid to flow through. It is made ofbrassforvalves that have to workwithlow pressures,whilein carbon steel forhigh pressures. Some models,instead,may be madeofsynthetic material such as PVC for working with non-corrosiveor colderfluids.3.The seal, directly connectedtothe shutter, allows the correct tighteningof the valve, so that there aren’t any leaks of fluid. It consists of two rings in plastic material likeTeflon.4.Above the shutter we find the stem, which connects the floating ball tothe lever used to operate the valve.5.The leverhandleis usually made of cast or molded aluminum forsmaller valves, while in durable anti-corrosive steel forbiggervalves. The operation of the ball valve is very simple, let's now see it in detail.Thevalve is installedin the middle of 2 pipes, keep in mind thatthisis not a controlvalve but rather a shut-offvalve, that is, it interrupts the fluid that flows inside it. To open or close the valve, the leverhandleat the topmust 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 valveincludes the water hammer: it is a shockwavecreatedbythe inertia of a liquid column in motion that crashes against a wall. When we closea globe valve, the liquid flow stops so quickly that the shockwavecan 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 holeof the shutterhas the same dimeter of the pipe.2.Reduced-bore valve, in which the holeof the shutteris smaller compared to the pipe’sdiameter. This type of valvereduces the speed of the fluid flowing internally.
We also find a third type of ball valvecalled Venturivalve, used to increase fluid pressure.It is named afterthe physicist Giovanni Battista Venturi,who discovered the relationshipbetween pressure and speedin the physics of fluids.The valve with the Venturi tubelooks like a normal ball valve, the onlydifferenceisfound inthe central diameter:the smallerdiameter causesthe liquid to increase its speed and once it reaches the larger section, the fluid will increase its pressurewhilelosing speed.Thistype of valve is used in filling stationsor in steamplants, where high pressure is required.The Venturi effect is called“hydrodynamic paradox”because it is believedthatpressure will increase in more constricted areasof the pipelinewhile 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 lubricationThey also have some disadvantages:•The water hammer, already mentioned above, is present in all types of fast closing valves•Whenused 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 coulddamage thevalve itself and the pipes connected to it.Do you know how many types of valves we use every day?