2 Position vs 3 Position Pneumatic Valves

Posted by OCPneunmatics on Jul 6th 2020

Are you using the right kind of pneumatic valve on each compressed air-driven system you have installed in your workshop? You might be surprised to learn that there are countless options regarding each type of pneumatic valve you’re likely to find.

Two-position and three-position pneumatic valves are among those you’re most likely considering for use with your system. Take a few moments to read a bit more about these different technologies. We’ve made sure to stock them both at SMC Pneumatics, so you shouldn’t have any difficulty with finding precisely the components that you need.

2 Position Valves for On/Off Controls

As the name suggests, traditional two-position valves are best for situations where you want a physical on-off control much as you might find on an electrical circuit. With a simple valve like this, you’ll find that these can be either open or closed. That being said, two-position valves could theoretically have more than two ports attached.

You might find a two-position valve with a virtually unlimited number of ports. Assume you had a valve with five different ports, one of which is an input area that allows air into your circuit. The two output ports are, by definition, constantly in opposite modes from one another. Whenever one receives air to the inlet, the other is connected in turn to the exhaust port.

Creative engineers might want to take advantage of this kind of system so that they can design complex two-state systems that take multiple actions depending on a specific setting. That’s a good idea for anyone who has to manage a large number of different tracks traveling along the same downstream line. You could switch different machines on or off based on what’s going on with a certain workflow in this way. A few people have even taken the time to design extremely complex systems using nothing more than 2 position pneumatic valves.

The fact that so many pieces make use of standardized fittings makes this kind of a construction project all the easier. More than likely, you’ll be able to identify a number of different situations where you can reorient a series of airflow gates simply by installing one of these modules.

A two-position directional valve could be looked at as a state machine if you’re familiar with this abstraction that’s been a favorite of engineers for many years. Finite state machines are always going to be in one of a certain number of states. In this case, the state is either on allowing air in or simply closed off. This makes it relatively easy to chart out the way that air is going to flow through one even if it has a number of ports attached to it.

In a way, three-position pneumatic valves are also finite state machines. That being said, they have an additional state to deal with.

Sophisticated 3 Position Valve Switches

Every three-position valve has an on and off position much like two-position valves do, which means you could theoretically use them in many of the same situations. What makes them different, however, is the presence of a center neutral position that blocks all ports. You might also find designs that offer a connection to both output ports directly to a center exhaust when the valve is not being actuated.

Some engineers prefer the so-called pressure held center closed three-position valves, which are perfect for inching operations. Technicians will sometimes need a cylinder rod to move to an intermediate position along a specific workflow and then slowly hold. Cylinder switches are also useful in these cases if you need to periodically sense the current position of a rod during the stroke.

Eventually, you might even come across five-ported four-way valves. These valves offer users the same basic level of flow path control along with the ability to control the motion of doubling-acting cylinders. With five ports, you might find that these units are able to provide dual-pressure control. One set level of pressure could be supplied to a cylinder while its in the process of extending then a different pressure will be applied during the retraction of the cycle. Users of these kinds of valves often rely on a common inlet pressure source and two separate exhaust ports.

An installation like this allows you to control the exhaust flow from each of the valve’s outlet ports. As a result, it’s a great idea for those who want to control the velocity of certain pneumatic cylinders by way of restriction.

At one point, engineers would have had to specify custom designs for each individual valve on their pneumatic layouts. That not only increased the cost of the equipment that they were working with, it also made things needlessly complicated. People had to wait through long lead times just to make sure that they were going to get the parts they were looking for.

Fortunately, because of high-quality manufacturing processes and an increased focus on the consumer, you won’t have to worry about these sorts of problems if you place an order. Chances are, SMC has the kinds of valves your looking for in stock even if they’re something that you might have been told you had to special order in the past.

Choosing Between 2 & 3 Position Pneumatic Valves

Those who do have to place special orders shouldn’t have any difficulty doing so, either. That being said, it’s always a good idea to take a second look at your design and see if you can build something around more standard pneumatic components.

In most cases, you’ll probably just need to use a two-position valve. If you’re trying to do something sophisticated, then you might want to consider using a two-position valve with additional ports or a traditional three-position valve.

Purchase Valve Types At SMC Pneumatics

SMC Pneumatics has special valves and more parts for your pneumatic system. In fact, you might even want to look at this as a potential opportunity to stock up so you won’t be left hanging the next time you have to install a healthy amount of pneumatic equipment and end up needing a large number of valves all for a single job.

Once you’ve picked out the kind of parts you need, make sure to contact us online to tell us more about your specific requirements. We’ll be sure to help you get a hold of all the valves that you’re looking for so you won’t have to worry about planning your next installation.

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