Electrohydraulics has always been known for moving heavy loads with a combination of high speed and precision. But now function safety has been thrown into the mix. And although you can find different valves from different manufacturers that that carry Safety Integrity Level (SIL) and Performance Level (PL) certification, officials at Atos SpA, Sesto Calende, Italy, say theirs is the only worldwide manufacturer offering a full range of directional and proportional valves designed for functional safety and certified by a notified body.
Machine Directive 2006/42/EC, along with relevant harmonized standards IEC 61508 SIL and ISO 13849 (PL), define the general principles concerning machine safety, which manufacturers should consider in limiting risk related to machine operation. Atos certified proportional valves meet these standards by performing the safety function in addition to axis-motion control. Because on-board diagnostics remain active even with no solenoid power, the valves confirm when a safe spool position has been reached. The valves are also certified by TÜV in compliance with ISO 13849 up to category 4, PL e and IEC 61508 up to SIL 2/SIL 3. These safety valves help in limiting potential risks to equipment or operators by preventing dangerous movements of electrohydraulic axes during production cycles or emergency conditions.
Certified safety valves eliminate the need for machine manufacturers to validate individual components to comply with the applicable safety standards. This saves considerable amounts of time during the machine design phase and the system certification process.
Of course, actual system SIL and PL levels do not depend only on the characteristics of single components, but also on the hydraulic system architecture and diagnostic coverage.