Long Live Pneumatic Cylinders

Environmental factors should be part of your pneumatic air cylinder specifications. Doing so will allow you to realize maximum life from the devices.

By Sarah Manuel, IMI Norgren

Pneumatic air cylinders are often taken for granted, until they fail. With some planning and forethought, cylinder life can be long, and performance kept at a high level. Before specifying/purchasing a cylinder, go beyond the application and give careful consideration to the environment in which the cylinder will operate. While we often are concerned about protecting the environment, in this case it’s important to protect your cylinders from the environment. Following are three environmental factors that affect air-cylinder life and performance and how to address them.

Temperature

While a typical plant may have an overall ambient temperature in the 70 F range, consider the exact placement of the cylinder and to what specific environmental factors it will be subjected. Does it operate in or near an area that experiences rising/high temperatures? A packaging application, for example, with a heat-sealing mechanism, would significantly elevate the ambient temperature. On the other hand, outdoor applications may dip well below the freezing mark in winter. Extreme temperatures translate to shorter cylinder life.

Certain metals, such as aluminum, tend to overstress when the temperature rises above 300 F. Applications such as this require stainless steel or other appropriate metals. When lubricants are subjected to high temperatures you may see a viscosity breakdown, leading to poor coating and increased internal friction.

Seals also suffer in extreme temperatures. The temperature at which your cylinders will operate dictates which of these three seal materials should be specified:

• Nitrile (buna N)—most commonly used seal material
• Fluoro-elastomer—400 F tolerance for intermittent exposure and 200 F for sustained operation
• Low-temp buna—designed to maintain elasticity at lower temperatures.

Chemicals

From caustic washdown solutions to common tap water, chemicals in your environment can adversely affect cylinder life. Anodized aluminum provides varying degrees of protection based on the level of anodization. Anodized clear coats provide some protection, while thicker hard coats are a more robust solution. Stainless steel represents one of the best, but costliest, solutions for combatting harsh chemical environments. Plastic heads, bearings, and endcaps can be used as metal substitutes in lower-weight, lower-friction applications.

Air quality

Elements in the atmosphere, compressor, and piping can adversely affect air quality. Water leads to corrosion, while particles can collect on cylinder seals. Proper filtration removes water and traps particles.

This is typically accomplished with filters that use centrifugal force toswirl incoming air in a bowl. The swirling action pulls 95% to 99% of the water out of the air. A second process forces the air through a filter to remove any particles

There is a wide range of filters available, ranging from very fine to coarse:

• 1 micron (very fine), for very sensitive application and/or process air
• 5 to 10 microns (fine), for sensitive applications
• 40+ microns (coarse), for general industrial applications. EP

Sarah Manuel is the Pneumatic Actuator Product Manager at IMI Norgren Precision Engineering, Littleton, CO. Learn more at imi-precision.com.