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Machinery safety: we've come a long way since 1979

03 September 2009

Steve Farrow charts the rise in sophistication of machinery safety systems over the past 30 years, and illustrates his article with the landmark advances in safety technology achieved by his own company during this period

Machinery safety has, thankfully, progressed a very long way in the last 30 years. In 1979 it was not uncommon to see machines with no guards, let alone an emergency stop button. Those machines that did benefit from such safety measures often had little more than an emergency stop button and a guard interlock connected as simple switches in the power circuit, rather than what we refer to today as a safety circuit. Of course some machines did have 'proper' safety circuits, with an arrangement of relays so that the circuit fulfilled the fail-safe function. And some benefited from the Pilz two-hand control relay, which was the first such product on the market when it was introduced in 1970.

In 1987 Pilz launched PNOZ, the world's first emergency stop relay. This was the first product designed specifically to monitor emergency stop switches and to perform safely in the event of a component failure. It had features such as positively guided contacts that enable the safety circuit to check the status of the relay. This product simplified circuit design, saved time, reduced costs and gave machine builders and their customers increased confidence in machinery safety. PNOZ rapidly became the most widely used safety relay, and the names 'Pilz' and 'PNOZ' became synonymous for safety relays.

In the wake of this development, an entire industry flourished, focused on fail-safe monitoring devices and input and output devices for machinery and processes. Pilz built on its initial PNOZ success with a number of product innovations, including the X range of safety relays, the PNOZelog solid-state safety relays (2002) and the PNOZsigma family of slimline, solid-state, multi-functional relays (2006).

Pilz also claims to be the first in the world to have launched a programmable safety-related control system - the PSS3000, which was introduced in 1995, followed by the SafetyBUS p open safety fieldbus in 1999. The PNOZmulti was the first software-configurable modular safety system when it was launched in 2002, and the SafetyEYE camera-based system for three-dimensional zone monitoring was yet another first in 2006.

This year Pilz introduced the PSS4000 Automation System and PAS4000 software suite, which together offer a new route to designing, programming and implementing an industrial automation system. It integrates safety, standard (ie non-safety) and motion control, as well as visualisation and diagnostics, with all data conveyed via a SafetyNET p industrial Ethernet-based fieldbus network.

Looking to the future, Pilz believes that future systems will bring simplified user operation and increased flexibility. In particular, safety and standard control functions, including motion control, will become closely integrated - as in the PSS4000 system. Closer integration of safety and standard control enables cost reductions to be made in hardware and engineering time. Furthermore, the software supports the system from the initial concept design right through detailed design, programming, commissioning and maintenance.

Something else we can look forward to is closer co-operation between man and machine. Already, systems such as SafetyEYE enable a robot to switch to a safe slow speed if an object (normally the operator) is sensed to be within a predefined zone around it. By developing this idea further, it can be seen that people and robots could in future work closely with each other, rather than remaining in their own zones. This offers the potential for higher productivity and improved cost-effectiveness.

Steve Farrow is general manager, Pilz Automation Technology


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