How to avoid mistakes when choosing pneumatic cylinders

Selecting the right pneumatic cylinder for your chosen application can be complex. Pneumatic cylinders come in thousands of variations, are used in a variety of applications and industries, and feature an even wider range of components. Each pneumatic cylinder type has unique specifications to suit different working environments. With all this in mind, PIF spoke to API Pneumatic UK about how to choose the right pneumatic cylinder to meet your requirements.

Pneumatic cylinder buying guidelines for first-time customers

API Pneumatic UK has years’ of industry knowledge and expertise, and can therefore provide a wealth of information around choosing a pneumatic cylinder to suit your process. According to API, here are some of the common mistakes you should avoid when choosing pneumatic cylinders for your application.

Improving the pneumatic cylinder selection

There is no single industry-recognised criteria to look out for when selecting a pneumatic cylinder. Instead, there are several individual factors that frequently appear within multiple purchasing guidelines among manufacturers, engineers and industry experts alike.

These include:

• The mass of the item to be actuated
• Available air pressure
• The distance the object has to move (stroke length)
• The envelope within which the cylinder is to operate
• Any possible side loading and look at mounting options to avoid it
• The speed of actuation must be established
• If the cylinder travel will be stopped by external, mechanical stops, or if it will rely on the cylinder end caps for end positioning
• The environment where the cylinder will operate (corrosive and/or extreme temperatures)

Ensuring the right pneumatic cylinder design

There are thousands of pneumatic cylinder variations on the market, so knowing your exact requirement is extremely important. First – choose the right pneumatic cylinder design and work from there. The most standard pneumatic cylinder design is a rod-style cylinder. These come in two distinct variants; single-acting and double-acting pneumatic cylinders.

Single-acting pneumatic cylinders are used to deliver motion in one direction only, whereas double-acting pneumatic cylinders are capable of providing both forward and backwards motions. When choosing the right model, you should first assess which of these two options would be most beneficial to your application.

Once you’ve decided between a single or double-acting pneumatic cylinder, you can begin to narrow down the type of rod-style cylinder design best suited to your process. For example, repairable pneumatic cylinders can generally be used in heavy-duty applications, due to the ability to replace seals and internal components – thereby prolonging cylinder lifespan. By comparison, lighter-duty applications tend to use disposable cylinders, as they cost less to manufacture. However, they do tend to be replaced more often due to their permanently sealed design.

Compact pneumatic cylinders might be preferred for smaller spaces, where short strokes are preferable. Guided cylinders are recommended for applications with either sizeable offset loads or for loads that require precise direction. Finally, rack and pinion style (or rotary) pneumatic cylinders are used to operate quarter-turn valves, often a requirement for applications found within the process industry. Rod-style pneumatic cylinders might be the most common design on the market, but rodless cylinders are also available for applications with either long stroke or high moment load requirements.

Understanding how your chosen pneumatic cylinder performs

The three things to measure when assessing the performance of pneumatic cylinders are:

1. Force output
2. Speed
3. Air consumption

Force output can be determined from the air pressure and bore size of a pneumatic cylinder. The general rule of when examining force output is that the generated force should be twice as much as the load. Stroking speed of a cylinder can be determined by dividing the airflow in standard cubic feet per minute by the piston area. For a simpler analysis, look at things like port sizes, inlet, tubing sizes and exhaust flow through control valves.

Pneumatic cylinder consumption has two factors: the volume of air displaced by the piston during operation and the volume of contaminated air that passes through valves, ports, tubing and cavities. If your chosen pneumatic cylinder can supply air even in a worst-case scenario, then optimal performance should be a guarantee for your chosen application.

Environments that typically require pneumatic cylinder applications

• Any application where the movement of a load is required
• Food machinery, for positioning product
• Conveying equipment, divert chutes, reject pushers, stop cylinders
• Opening and closing sliding doors on process machinery
• Safety interlocks on access doors
• Clamping of workpieces
• Pneumatic presses
• Assembly fixtures
• Robotic manipulation
• Opening and closing of process valves
• Safety shut off circuits in hazardous environments
• Pneumatic lifting equipment

What else you need to consider

API Pneumatic UK also advises looking at the mounting configurations of your chosen pneumatic cylinder. Standard mountings traditionally ensure cylinders can execute specific movements that your application requires. Position feedback and cushioning are also factors that you might want to consider, as both can influence what type of performance a cylinder might be able to deliver. For example, magnetic cylinders are capable of different types of position feedback when compared to non-magnetic cylinders. Cylinders with cushioning can prevent damaging metal-to-metal contact with end covers, which would normally result in potential mechanical damage.

Adding his thoughts on how customers should choose a pneumatic cylinder, Tim Swift of API UK had this to say: “With all the above taken into consideration, if the load to be moved relies upon the full cylinder stroke and end caps for positioning, cylinders with internal pneumatic cushioning will be required. In this instance, standard ISO 15552 cylinders would be suitable.”

Where to find pneumatic cylinders from API UK

API UK has one of the most extensive portfolios of pneumatic cylinders, accessories and components available anywhere on the market. They can match the right pneumatic cylinder type with your desired application or process. For more information, take a look at their pneumatic cylinder selection, or speak to the team directly on 01782 206 995.