When selecting a pneumatic cylinder, it’s important to consider all aspects of the operating environment to ensure you make the correct choice. Environmental factors can sometimes be overlooked when selecting a pneumatic cylinder, but they are important if design engineers want to optimize operation, maximize working life and ensure reliability.
The factors to consider include ambient temperature, operating media/chemicals and other fluids or materials present.
For a standard cylinder, fundamental performance characteristics are often specified for an operating temperature range of -20°C to 80°C. However, if your application operates beyond this limit then it’s important to optimize for a variant designed to scope with more challenging applications.
There are some pneumatic cylinder product variants that, with the help of specific higher performance lubricants and special sealing materials, can operate effectively in either extreme low temperature environments (down to -40°C) or in higher temperature environments (up to 150°C).
Our P1F, an ISO 15552 profile cylinder for high and low temperature applications with corrosion resistant body for harsh conditions, is one such cylinder.
When operating in a potentially corrosive environment, you need to consider a final product selection specially designed for the challenge. In a dry and ‘non-aggressive’ environment, a cylinder with a chromium steel piston rod will normally suffice.
However, in humid operating environments such as those with risk of salt spray, all external cylinder surfaces will need to be coated, and the piston rod should be made of stainless steel.
In other applications, deposits on the piston rod can cause issues, e.g., sugar sediment in food equipment or resins, asphalts and even cement in other applications. To alleviate this problem, options exist to install metal scraper rings as opposed to plastic or rubber versions with the piston rod seal to remove the residue before it can cause damage to the cylinder assembly.
In food and beverage production, where specific technology of the pneumatic cylinder may be required, you need to choose a variant with special ‘clean’ design features that reduce the amount of entrapment points for bacteria.
A further challenge in food production environments is the frequent washing of the work area, which can lead to damage to static and dynamic gaskets and seals. As a result, engineers may need to select a cylinder with a self-lubricating piston and therefore designed for dry rod operation, such as our P1F with dry runner scraper, an ISO 15552 profile cylinder suitable for non food area EN1672-2. The P1S Series of stainless steel pneumatic cylinders provide better corrosion resistance and are safe to be used in close proximity to the food process.
An atmosphere with the potential to become explosive during operating conditions (or under the influence of those surroundings) requires a pneumatic cylinder that is ATEX-rated. These environments usually include chemical plants, mines and flour mills. Products covered by directive 94/9/EC are defined as intended for use in potentially explosive atmospheres.
The challenges for pneumatic cylinders are as numerous as the sectors in which they are needed to operate. Downtime costs money and lost production must be avoided for anything other than routine maintenance. Hence careful selection based on operating requirements and prevailing environmental factors must be given proper attention from the outset.
Article contributed by Rebecca Hammes, Business Unit Manager for Actuators, Pneumatic Division Europe, Parker Hannifin Corporation.