The way to a safe machine

A machine must be verifiably safe; i.e. it must perform an intended function without jeopardizing the safety and health of persons. What is the best approach to ensure a safe machine, and which standards help you to construct a machine which is safe for its entire life cycle?

The following schematic representation should provide you with an overview of the relevant safety standards.

Design and risk assessment of the machine to
EN ISO 12100-1, EN ISO 14121

EN ISO 12100-1:2003: Safety of machinery, basic terminology, general design guideline
EN ISO 14121:2007: Safety of machinery, Risk assessment

  • Determination of the limits of the machine (what is the intended purpose of the machine?)
  • Identification of the hazards on the machine (exposing potential dangers)
  • Risk assessment to EN ISO 14121
  • Risk estimation (damage extent x occurrence probability)
  • Risk evaluation (risk reduction necessary)
  • Decisions relating to the measures for risk reduction (through design measures, protective devices).

Function and safety-related demands for safety-relevant control

EN ISO 13849-1/-2:2006 Safety of machinery
Safety-related parts of control systems
Part 1: General principles for design
Part 2: Validation

IEC 62061:2005 Safety of machinery Functional safety of safety-related electrical, electronic and programmable electronic control systems

  • Definition of the type of safety functions
  • Demands placed on the control architecture / hardware structure
  • Demands on the diagnostic functions

The definition of safety functions on the control and their implementation are described in the listed international standards.

Design and implementation of safety relevant controls

The EN 954-1 established itself as the internationally accepted state-of-the-art standard in the field of machine safety. At the end of 2006, the successor standard EN ISO 13849-1:2006 was officially accepted and listed in the official journal of the European Union as a harmonized standard.
The EN 954-1 may be applied until 30.11.2009.

In the EN ISO 13849-1:2006 standard, the degree of risk reduction is specified as the Performance Level (PL ae). The IEC 62061:2005 standard serves as an alternative for the EN ISO 13849-1:2006. The technical safety performance is described as the Safety Integrity Level SIL in three stages (1, 2, 3).

Recommended application and selection of standards
The application of each of the EN ISO 13849 and IEC 62061 standards allows the assumption of compliance to the fundamental safety demands in the machinery directive.

When are each of the standards used?
For selection please examine the following tables which shows a comparison of the fields of application of both standards.

EN ISO 13849-1:2006 IEC 62061:2005
Applicable to hydraulic, pneumatic and electromechanical systems without restriction. Only applicable to electrical, electronic and programmable electronic systems.
Applicable to programmable electronic systems only with restrictions. Specific architecture only up to PL d. Possible use of EN ISO 13849 with mixed systems.
Calculation concept based on specified architectures. Any architecture possible.
Suitable for the safety certification of devices and the entire safety function using tables. Suitable for the safety certification of devices and the entire safety function using calculations.

Electrical safety aspects to IEC 60204-1

IEC 60204-1:2006 Safety of machinery Electrical equipment of machines

The reliability of the protective function does not just depend on the selected equipment and circuitry.
Please consider further factors which are described in the IEC 60204-1.

The necessity of applying safety functions to a machine result from the risk assessment from which the demands on the safety functions can be derived. Standards can be applied for the implementation and as proof of compliance to the demands.

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