Safety of machinery - a review of the guide from Lenze

Lenze has published a new guide, Safety of machinery, to help machine builders and system integrators prepare for the functional safety standards that are replacing EN 954-1 ( Safety of machinery. Safety related parts of control systems. General principles for design). Both of the functional safety standards EN ISO 13849-1 ( Safety of machinery. Safety-related parts of control systems. General principles for design) and EN 62061 ( Safety of machinery. Functional safety of safety-related electrical, electronic and programmable electronic control systems) are harmonised to the new Machinery Directive 2006/42/EC that comes into force on 29 December 2009, so there is a pressing need for designers to understand the principles of functional safety as applied to machinery.

Within Lenze's guide there is a brief history of EN ISO 13849-1 and EN (IEC) 62061, together with an explanation of the overlap between the standards and an indication of the types of application for which each standard might be applicable.

What follows is a useful step-by-step overview of the route to be followed when designing a safe machine. These are presented as:

1. Risk assessment and evaluation in accordance with EN 1050/EN ISO 14121
2. Minimising risk
3. Implementation in control systems
4. Specification of safety functions
5. Determining the achieved performance level (PL)
6. Verification and validation

Drive-based safety

Unlike some other machinery safety guides, the document from Lenze also looks at safety functions for adjustable speed electrical power drive systems; these are not described in EN ISO 13849-1 but in the separate standard EN 61800-5-2 ( Adjustable speed electrical power drive systems. Safety Requirements. Functional). Included in the Lenze guide is a useful table that lists the various terms found in EN 61800-5-2 - such as Safe torque off, Safety-limited acceleration and Safe cam - and provides an explanation and the three-character abbreviation.

For engineers not already familiar with it, the guide also presents information about SISTEMA (Safety Integrity Software Tool for the Evaluation of Machine Applications), which is available free of charge from the BGIA (Berufsgenossenschaftliches Institut fr

Arbeitsschutz - the Institute for Occupational Safety and Health) in St Augustin, Germany. This tool can be used to determine the performance level in a machine, with dialogue boxes guiding the user through the process of creating the individual safety functions and entering the safety-relevant parameters. Lenze says it can provide support for the SISTEMA tool in the form of a SISTEMA library containing all Lenze components that have already been certified in accordance with the latest standards.

In addition, Lenze is supporting TUV Rheinland's development of a database of safety-relevant parameters for use in designs to EN ISO 13849-1.

At the back of the Lenze guide is an appendix with a list of abbreviations and links to relevant websites.

This free guide is certainly worth requesting, especially if you are not yet fully prepared for the switch from EN 954-1 to the functional safety standards EN ISO 13849-1 and EN 62061. It will also be particularly helpful for machine builders and system integrators who are using - or planning to use - inverter drive-based safety. Contact Lenze to request your copy of Safety of machinery by telephoning +44 (0)1234 321321 or emailing [email protected].