Cylinder Accessories

Even when a cylinder is sized properly, it may stroke too fast and require use of a flow control, typically by controlling flow of air leaving the cylinder. This also reduces noise problems caused by cylinders banging and reduces rapid exhaust racket. These flow controls are typically mounted directly to the cylinder, but can also be mounted inline near the cylinder, or at the valve if the hose between the valve and cylinder is less than about 3 feet.

Specifying cylinders with built-in cushions can help provide long-term performance in high-speed pneumatic motion applications. The cushions allow a cylinder to stroke at high speed and only slow down near the end of stroke for a quiet, low-impact stop. Adjustable pneumatic cushions are often the best solution, comprised of specially designed end caps with built-in flow controls. Mufflers can also be used to quiet cylinder or valve exhaust noise, and they are often a simple and low cost solution.

Cylinder position switches are extremely helpful in sequencing operations and prevent starting the stroke of one cylinder before the previous cylinder’s stroke is complete. Using timers to control a sequence instead of position sensors should be avoided in this and most cases. One stuck or slow cylinder during an automated sequence can cause a machine crash, costing much more than the cost of buying, installing and programming end-of-stroke sensors.

These are just a few of the many items to consider when designing a successful pneumatic system. Other factors, such as energy efficiency, can affect overall system design as well. But regardless of the design, watch out for the common issues and always be sure to supply, prep and distribute the air properly. When properly applied, your pneumatic devices and actuators will have a long life with limited operational issues along the way, and with minimal required maintenance.

These are just a few of the many items to consider when designing a successful pneumatic system. Other factors, such as energy efficiency, can affect overall system design as well. But regardless of the design, watch out for the common issues and always be sure to supply, prep and distribute the air properly. When properly applied, your pneumatic devices and actuators will have a long life with limited operational issues along the way, and with minimal required maintenance.

Control Valves

Once the cylinders are selected, you should now have a good idea of the flow rate and pressure of compressed air needed. With this information, you can select control valves. Items to consider in valve selection are size (flow capacity), type and actuation method.

Choosing the right type of valve for the job required is not as difficult as it may seem. For cylinder control, the simplest method is to use a 3-way valve for a single-acting cylinder and a 4-way valve for a double-acting cylinder. Systems can be much more complex if needed, but let’s focus on a basic system for now. The form factor of the valve can vary a great deal and many people have a variety of preferences. It’s usually best to make sure the valve has the needed performance characteristics before locking into a particular form factor.

Valve Sizing

Once the function of the valve has been determined, look at the required flow capacity. The usual first step is to use the air cylinder bore, stroke and cycle rate to determine a flow rate in standard cubic feet per minute (SCFM). Many valve suppliers will list a flow rate at a particular inlet pressure and pressure drop. Others will list this value as a factor Cv, which has no units. For a more thorough explanation, check out our Interactive Cv Calculator here. A simple thing to remember is that a larger Cv value will allow a higher flow rate of air through the valve. Key points to remember in valve sizing are that undersized valves may restrict flow and not allow a system to work properly. Oversized valves often cost more and will use more air. Keep in mind that air consumption is a major portion of the expense for a pneumatic system. If air consumption is a major concern for your factory, check out our Interactive Air Consumption Calculator here.

Valve Actuation

How will the valves be operated? Manual valves could be push button, lever or foot pedal activated. The more common method is to use electric solenoids to operate the valve. Solenoids are available in a variety of both AC and DC voltage ratings to fit just about any need. Match the solenoids up with your electrical control system. In less common situations, an air piloted valve may be required. When air pressure is applied to a pilot port, the valve switches. This is a good way to switch very large valves while using very little electrical power – use a small solenoid valve to send air to the pilot port of the large valve.

(FROM INTERNET)