Functional Safety for Machinery
Ensuring the safety of an industrial process through the use of safety instrumented systems.
A machine according to the Machinery Directive is an assembly of linked parts, from which at least one must be movable, with the appropriate actuators, control and power circuits.
The manufacturer or the party that puts the machine on the market is obliged to meet the essential safety and health requirements not only of the Machinery Directive but also of all other relevant European Directives. It is required that the manufacturer or the party that puts the machine into market can demonstrate with appropriately detailed documentation, calculations and drawings, how the product complies with all relevant Directives, and so is safe during all phases of its life.
A systematic analysis is necessary in order to identify all dangers and risks, which originate from the machine. Under consideration of these dangers the machine has to be designed and constructed in such a manner, that all dangers are eliminated or at least are limited to a minimum.
Regarding functional safety for machinery there are two possible standards that can be used to demonstrate conformity with the Machinery Directive, these standards are EN/ISO 13849 and EN/IEC 62061.
Basic Technical Concepts
EN ISO 13849-1 can be applied to pneumatic, hydraulic, mechanical as well as electrical systems whereas IEC/EN 62061 is limited to electrical systems
The methodology of EN ISO 13849-1 is intended to provide a more direct and a not so complicated route for those who have a more conventional safety functionality implemented by conventional technology whereas the methodology in IEC/EN 62061 is intended to allow for complex safety functionality which implemented by more complex system architectures.
EN ISO 13849-1 uses the term performance level to define the trustworthiness of the safety function. There are five performance levels a to e, where performance level a is the lowest and performance level e is the highest. IEC/EN 62061 describes both the amount of risk to be reduced and the ability of a control system to reduce that risk in terms of SIL (Safety Integrity Level). There are three SILs used in the machinery sector, SIL 1 is the lowest and SIL 3 is the highest.