John Hill, marketing services manager for Parker Hannifin’s Pneumatics Division, explains how this year’s additions to the Directive will improve machine integrity and enhance safety
The aim of the Machinery Directive is to improve safety by raising the quality and efficiency of machine equipment. Two standards have been referenced in the Machinery Directive for 2011 to continue the drive towards this goal. The standards within Machinery Directive 2006/42/EC (formerly 98/37/EC) will impact on all those involved in the design, manufacture and operation of machinery with moving parts with responsibility for compliance being with the builders of systems. With that in mind, let’s look at what the new standards demand and consider how they will be applied in practice.
The principal revision to the Directive is the replacement of EN 954-1. This was replaced because, while it covered safety related elements of machine control systems, it omitted factors such as the use of electronic controls, testing intervals, life cycles, and the probability of component failure. To remedy the situation, EN 954-1 has been replaced by 2006/42/EC which references the two standards, EN 13849-1 and EN 62061, covering a specific group of systems.
EN 13849-1 covers the general design principles for machine safety and safety related control systems, including pneumatics and hydraulics, while EN 62061 defines the functional control of electrical, electronic and programmable electronic control systems only. The standards extend procedures for risk assessment, with these now having to be specified as Performance Level (PL) in the case of EN 13849-1, or Safety Integrity Level (SIL) for EN 62061. These ratings will be associated with a given safety function, with definitions for diagnostics capabilities and common cause failures.
These additions to the Directive will create a framework that has to be followed for functional safety and related parts of control systems, with the focus being on common sense safety principles, such as redundancy, diversity and fail safe behaviours. EN 13849-1 examines complete ‘input/function/output’ safety functions, including all the components involved in their design. EN ISO 13849-1 goes beyond the qualitative approach of EN 954-1 to include a quantitative assessment of the safety functions.
The Machinery Directive now clearly specifies EHSR (Essential Health and Safety Requirements) for assemblies of machines; this means that such assemblies must now be considered as whole new machines and CE marked, and it is the legal responsibility of the system builder to ensure compliance. It is therefore important that machine builders involve their suppliers from the earliest design stages to ensure that the reliability and safety of the complete machine structures are considered from the outset. This can be achieved by the selection of proven, reliable components and safety principles that minimise the manifestation of critical faults.
The new standards have been phased in during 2011 and will make a positive impact on the activities of both end users and machine builders; while customers gain the reassurance that each machine will operate in a safe manner, machine builders gain a degree of protection from litigation in the event of an accident arising through machine failure or misuse.