Smarter options for machine safety
Author : Paul Considine of Wieland Electric
11 September 2009
From 29th December 2009 owners and users of machinery, as well as machine manufacturers, will need to ensure they are compliant with the new EU Machinery Directive.
Paul Considine
Until that time, machine safety in the UK is covered by EN 954-1, but this has certain failings. The key factor is that EN 954-1 was based on calculated risk, setting appropriate system behaviours against categories. However, with increased use of programmable electronics it is no longer possible to measure safety purely in terms of this simple category system. Just as importantly, this approach was unable to provide information on probability of failure.
Consequently, the EU Machinery Directive requires risk assessment in accordance with the new harmonised standards EN ISO 13849-1 (Safety-related parts of control systems, Part 1: General principles for design) and EN 62061 Functional safety of safety-related electrical, electronic and programmable electronic control systems).
Thus, EN ISO 13849-1 is based on the familiar categories from EN 954-1 and examines complete safety functions, including all of their components – while also including quantitative assessment of safety functions.
EN 62061 defines requirements and provides recommendations for the design, integration and validation of safety-related electrical, electronic and programmable electronic control systems for machinery. It is based on a combination of qualitative and quantitative examination of safety-related electrical and electronic control systems, from the initial concept through to final decommissioning. Each safety function is divided into sub-functions which are assigned to actual devices.
While this is just a snapshot of the new regulations, it does illustrate their complexity but, as I noted earlier, there are now technologies that can make compliance much easier in new and existing systems.
Without a doubt, the primary consideration is always that the safety systems are operating properly at every level. And it’s certainly more efficient and convenient if all of these levels, or sub-functions, can be addressed through the same system.
So, when there is a fault in the system it’s vital that the whole system closes down until safety can be assured. However, any such downtime can be very expensive. Consequently, it also makes sense to have effective fault diagnosis built into the system – ideally the same system that is responsible for safety-related control functions.
This is where technology can lend a very cost-effective helping hand and while there have been electronic monitoring systems available they have been very expensive. Now there are relatively low-priced, computer-based systems that will take care of all of the safety monitoring and fault diagnosis, continually monitoring every aspect of safety from post-top emergency buttons to light beams on conveyors, while also locating and diagnosing faults.
Another benefit of such a system is that it can be used from the early design stages, before the plant ‘goes live’. Simulation functionality enables the designers to run through the operations and identify any potential problem areas before they cause a real problem.
At a time when it’s important to reduce overheads and maximise productivity it makes perfect sense to look at smarter ways of doing things, and to find more cost-effective ways of achieving compliance with legislation. Taking advantage of the latest technologies is the obvious way forward.
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