What is a Spool Valve?

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Spool valves are found in almost every industry you can imagine performing a wide range of tasks.

Spool valves can be used in both hydraulics (where oil is the energy source) or Pneumatics (where the air is the energy source) and their job is to control the flow direction of the energy source by combining or switching the paths through which the oil or air can travel.

Essentially a spool valve is a cylinder inside a sealed outer case.

There are several chambers drilled through the case from one side to the other; these are commonly known as ports.

A spool valve can be operated in a number of ways, we could use a button, a lever or by way of a solenoid.

Whatever the method is chosen to control the valve, all that we are doing is simply pushing the spool to move within the housing, and by doing this we are allowing or blocking the path between the ports.

In some cases, there may be a solenoid at each end of the valve, whereas in others there is a spring return so when the solenoid is no longer pushing the actuator the spring will return the spool to its “normal” or rest position.

Imagine the example of extending a pneumatic cylinder using a spool valve.

The Pneumatic air supply is connected to the inlet port 1.

Port 2 is connected to the pneumatic cylinder extend connection.

Port 3 is unconnected as it is the exhaust port.

In the normal state without the actuator being operated nothing will happen as the spool is physically blocking the airflow at port 1 and the cylinder is retraced because ports 2 and 3 are connected due to the spool position.

So any air already within the system would escape to the atmosphere through the exhaust port. Let’s consider this the “normal” or rest position.

Now imagine we operate the actuator. We would see the spool position changes and the cylinder extends.

This is because the spool has moved position unblocking port 1 and simultaneously blocking port 3 resulting in allowing airflow from port 1 to port 2 while blocking the exhaust.

This is known as our working position.

The cylinder will remain extended until the spool is moved back to the normal position, either by way of another actuator at the opposite end of the valve or by an internal spring return.

In our example, this type of valve would be known as a 3/2 valve because we have 3 ports and 2 spool positions.

Spool valves are usually referred to by the nomenclature 3/2 or 5/3 etc., where the first number relates to the number of ports and the second to the number of different spool positions.

The blocking parts of the spool are known as “lands”, which are raised above the spool core; if these are made different in configurations they can change the way the port pathways interconnect.

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#RealPars #automation #SpoolValve

[hangumanga]

After watching so many YouTubes about 3/2 DCV, this is the most easy-to-understand video which really made me apprehend the concept of the spool operation. I am sure the upcoming engineers, technicians and students would find your explanation so interesting and understable. Thank you very much for the videos!

[carefreestudios]

As someone who repairs industrial controls and instrumentation it is the little mini spool valve inside the positioner that is usually the problem when valve positioners fail to work and cleaning the spool valve which sometimes get "gummy" with some isopropyl alcohol so it can freely move you can save often save yourself the cost of repair or replacement

[amitanaudiophile]

Thanks a tons. This is one of the best way to educate next generation instrumentation people, young engineers. Hat's off to you for such valuable uploads. Many thanks and all the best for you.

[bsir]

Thanks for this brief introduction of spool valve. I am from Hong Kong but now studying in Canada, studying automotive services. Alex

[miguelherrerajr.]

Hi everyone !!! 😃
It's the first time I have tried to understand how the spool valves work. I just can say was very easy to understand and comprehend.
Thank you very much. 👍👍

[ziborgbe]

Many thanks for this video. I straggled to understand and remember the theory behind spool valves. In this condensed version i have grasped the idea and technical terms linked to it.

[ОлександрПідгородецький-кй]

Great channel! Some period of time ago I started to work on the plant. I suggest that 95% of your videos are connected with real situations and very useful. Good luck!

[randhirpatil]

kindly add content that explains, how to control the speed of hydraulic cylinder using spool valves. Also please explain selection guidance for solenoid spool valves in the hydraulic application.

[nathansmith]

Thanks for the info. I was wondering what the spool looked like!

[oktaytekin]

As everytime this lesson is been wonderful.Thank you very much.(ln İstanbul)

[Redline]

Thank you. Wanted to learn more about characteristics in general and understand differences of spool vs poppet wrt internal leakage. This helps.

[rafaelcastro]

Thank you for the very clear explanation in the videos

[jury]

Thanks for Great It will be helpful for my work and I will recommend this video to my colleagues!!

[prkreddy]

I am always get confused about now it's clear.... TQ

[tusharsontakke]

Make a video on detail about the hydraulic and pneumatic system. Most informative channel on youtube.

[yehtutnaung]

Another awesome video, thanks RealPars

[alanzube]

This is excellent stuff. Keep the coming!

[derina.maleek]

Spool valves I never hear this device
Thank realpars

[MrBooojangles]

Thanks. I never knew how they worked before and now I do. I do have a problem with one lever, or one spool on a two spool auxiliary block I have on my tractor. One of my levers has recently become stiffer to move. The whole block operates my front loader hydraulic rams. The other day it actually stuck in a working position and the ram carried on further then I wanted and had to quick put the lever back to the rest position by hand. Since then, it's moved a little easier, but the lever still doesn't go fully in to the rest position. I also notice that ram is working a bit slower in one direction then the other. Its a double acting ram. Do you think it's the levers pivot pin at fault, or the return spring of the spool gone weak, or are there any rubber seals inside that may have got worn. The other one on the block still moves freely as it should.

[chemistryinstruments]

Just what I was looking for, working on some of them