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Functional Pneumatic Safety in Machine Automation

Safety is a hot topic and ISO 13849-1 / 13849-2 has become the primary standard driving pneumatic functional safety within the machine automation space.  Functional safety provides machine builders and users the freedom to satisfy the requirements of safety standards in various ways.  The traditional way to render machinery safe is to release energy.  This may not always be the best or most efficient solution, as it does not always prevent unwanted motion during the “energy releasing” phase or allow a predefined safety position to be achieved.

The move to functional safety in pneumatic circuits has great potential to improve machine efficiency.  Historically, the go-to solution for safety in pneumatic equipment was to employ a dump valve that releases all pressure.  This solution often negatively affects machine efficiency, especially in situations with frequent operator intervention such as load/unload stations.  Releasing pneumatic energy exhausts compressed air which must be recharged upon start-up.  This process costs money and decreases machine cycle time.

There are three basic safety functions in pneumatic circuits – release of energy, return home, and stop/inhibit motion.  Depending on a machine’s pneumatic content, any of these safety functions could be the most efficient and safest method.

The traditional dump valve / release energy solution is the best solution for some applications.  In many instances, however, it would be more efficient to stop/inhibit motion, return home or use some combination of the safety functions tailored to the specific safety requirements of the equipment.  It is sometimes also more efficient to inhibit specific portions of a machine while the rest of the machine operates normally.

ASCO’s Zoned Safety manifold allows users to define and setup multiple, independent safety functions in up to 3 discrete safety zones all within one valve manifold.  This solution can achieve up to Category 3, PLd, as defined by the ISO 13849 Functional Safety specification.  This basically means that each zone in the manifold can provide a custom redundant functional safety solution with appropriate diagnostic coverage (DC).  This is a suitable solution for most manual load/unload stations and a wide variety of other industrial applications.

Using ASCO’s Zoned Safety concept, it is possible to customize a solution that is both safe AND efficient:

  • Streamline plumbing by working safety into an existing pneumatic manifold
  • Incorporate up to 3 safety zones into one valve manifold and setup non-safety zone valves on the same manifold for those functions that must not shut-off (e.g. vacuum holding force)
  • Provide multiple and independent safety functions as needed
  • Reduce compressed air usage
  • Minimize restart times to increase throughput
  • Is compatible with various fieldbus protocols

You can connect directly with an ASCO application specialist or join the Fluid Control & Pneumatics group in the Emerson Exchange 365 community for more information.