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Safety

Three tips for designing a trouble-free pneumatics system

Speed, force, and size are vital to the compressed air system, but so are external, internal, and safety considerations.

By Darren O’Driscoll September 10, 2020
Courtesy: Festo

 

Learning Objectives

  • Pneumatic design has external and internal design considerations the user must consider.
  • External considerations can’t be controlled, but internal ones can. In both cases, the user and designer must adjust to their surroundings.
  • Perform a risk assessment and design for safety.

If designing pneumatic systems were about incorporating size and flow to control an actuator’s speed and force, then every new or retrofitted pneumatic system would be perfect every time. Controlling pneumatic systems, however, is more complex because there are external, internal, and safety factors affecting performance. The three tips highlighted can help guide the pneumatic system design process for users.

The Festo MPA-C valve terminals are rated IP69K and can be mounted directly on a machine in a washdown environment. Courtesy: Festo

The Festo MPA-C valve terminals are rated IP69K and can be mounted directly on a machine in a washdown environment. Courtesy: Festo

Tip #1: Understand the external considerations – factors one has no control over

Control engineers always should consider two external focus areas during the design process. The first external area of design consideration involves the industry in which the machine will be used.

Most industries have standards the designer must adhere to. The food industry, for example, requires conformance to various food safety guidelines. The automobile industry has any number of performance standards. The mining, battery, medical, and lab automation markets all differ. Research the standards and the norms for the industry where the machine will operate and design accordingly.

The Festo CRDSNU cylinder has FDA compliant NSH-H1 lubricating grease and dry run wiper seals for food safe production. Courtesy: Festo

The Festo CRDSNU cylinder has FDA compliant NSH-H1 lubricating grease and dry run wiper seals for food safe production. Courtesy: Festo

The second external area the control engineer has no control over, but must account for, is the physical environment. Heat, cold, humidity, dryness, dustiness, corrosive atmosphere, harsh chemical washdown, inside versus outside location and food contact are among the environmental factors that may impact performance. Understand the factors that contribute to the physical environment of the new or retrofit pneumatic system and do so recognizing these conditions may vary depending on the time of year.

Microscopic cracks in tubing point to the importance of proper component selection for the environment. Courtesy: Festo

Microscopic cracks in tubing point to the importance of proper component selection for the environment. Courtesy: Festo

Tip #2: Factor into the design those internal considerations under the control of the designer

Many considerations of the pneumatic system are under the engineer’s control. These include air quality, tubing material, routing, size, component accessibility and availability.

Compressed air contains moisture, dirt particles, and oil. Any one or combination of these contaminants can degrade pneumatic system performance. Building in air filtration – referred to as air preparation systems – that meets the performance specifications of the components in the system. Refer to ISO 8573-1 Compressed Air –Part 1: Contaminants and Purity Classes as an important design standard. Once the desired air purity for the components is determined in terms of concentration of dirt, water, and oil in the air. There are software programs that can identify the specific air preparation filters required to reach those levels.

Tubing is just as important in design consideration. For example, harsh chemicals or corrosive compounds in the environment can cause tubing to crack and leak. Specify the best material for the environment. Long runs of tubing reduces air flow. The goal is to create the shortest, straightest runs from air preparation unit to valve. If it is impossible to shorten a run, increase tube diameter to compensate. Kinks and bends reduces the internal cross-sectional dimension and reduces flow. Increase diameter as appropriate to achieve desired flow.

End users depend on the control engineer to think about the future where components will have to be serviced or replaced. Adhere to these three design principles:

  • Ensure components are easy to access and replace.
  • Specify standard off-the-shelf components, components that can be quickly delivered from the supplier. This will ensure minimized downtime.
  • Consider the application of the new class of smart sensors that can warn of future failure and reduce the risk of unplanned shutdown.
Air preparation units, like this MS6 assembly with quick exhaust safety valve, are vital to extended, trouble-free performance. Courtesy: Festo

Air preparation units, like this MS6 assembly with quick exhaust safety valve, are vital to extended, trouble-free performance. Courtesy: Festo

Tip #3: Perform a risk assessment and design for safety

In terms of external considerations, a controls engineer should research the standards for the industry and the machine’s environment and plan accordingly. Perform a thorough risk analysis to determine the required performance level and specify components that meet the requirements.

This step is where the designer has control. Enlist the aid of safety specialists working for the components’ supplier to assist in safety component specification. The next time the new machine or retrofit process begins, remember to consider the external, internal and safety factors that must be included when designing a trouble-free pneumatic system.

Darren O’Driscoll is a product market manager at Festo. Edited by Chris Vavra, associate editor, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com.

MORE ANSWERS 

Keywords: machine pneumatics, machine safety

Pneumatic design has external and internal design considerations the user must consider.

External considerations can’t be controlled, but internal ones can. In both cases, the user and designer must adjust to their surroundings.

Perform a risk assessment and design for safety.

CONSIDER THIS 

What methods do you use for ensuring pneumatic systems work properly?


Darren O’Driscoll
Author Bio: Darren O’Driscoll is a product market manager at Festo, focusing on pneumatic actuators for the North American Cluster and supporting air supply products for the Canadian market. O’Driscoll has 25-plus years experience in product management in the fluid power industry, most recently specializing in pneumatic factory automation.