Five steps to a safe machine


About APS & Lenze

From the safety function to the product: Our products with safety engineering.

The Machinery Directive comprises the following elements:

  • Carrying out a risk assessment: this enables you to identify applicable safety and health protection requirements.
  • Design and construction of the machine that takes into account the results of the risk assessment.

Following the risk assessment, you will know what measures you need to implement to reduce the risks.

If you cannot implement these measures in the design phase, then it will be necessary to integrate them into the control technology and set them down in writing in the specifications for the safety functions.

When using a control system, the Performance Level (PL) determines the requirements that the measures will need to meet in order to reduce risk. Following the implementation of safety functions, the real achieved PL will be checked and must be at least the same or greater than that worked out in theory beforehand.

1. Assessment of risk and risk reduction

The first step to a safe machine is establishing the limits of the machine and in particular its application as directed. This includes, for example, its application area, operating modes, service life and the interface between people and machine.

Using these specifications, you can identify points of danger and evaluate the risk of each individual danger. If it turns out that the risk would be too great without implementing additional measures, then the said risk must be reduced to an acceptable level.

The measures taken should prevent the danger entirely or reduce it by using an inherently safe design. Only if these measures do not lead to sufficient reduction of the risk should you rely on technical protective measures and – as a last resort – the documentation.

2. Safety concept

Safety concept

If the technical protective measures require the use of a control system, then the safety functions to be controlled by the control system should be described in precise detail. The required Performance Level (PL) for each safety function will then be established according to the DIN EN ISO 13849-1 graphs.

Following selection of the control system and all components that influence the safety function, checks will be carried out to see if the identified Performance Level is adhered to during implementation and verification.

3. Validation planning

Following selection of the control system and components, you will plan the validation.

In doing so, you will need to specify the following:

  • How documents are identified and updated?
  • In which ambient conditions the validation should take place?
  • Which checks and measuring tools are to be used?
  • Which standards should be used (e.g. DIN EN ISO 13849-2 for control systems)?
  • Who are the people responsible?

4. Implementation and verification

Six steps to a safe machine: 3. Control system-based implementation

The implementation of the planned measures must then be carried out e.g. the safety control should be programmed and the safe drive parameterised.

As part of verification, you should check whether the planned measures have been correctly implemented. If they have, it should be confirmed that the Performance Level of the implemented safety functions is better or equal to the Performance Level identified when drawing up the safety concept.

5. Validation

Lenze safety engineering

Validation is carried out according to the specified planning. If checks are not passed, rectification will be required.

All validation activities must be documented. Successful validation is concluded with a validation report.

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