Feature Machine safety New standards for Machinery Directive
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
T
he aim of the Machinery Directive is to improve safety by raising the quality and efficiency of machine equipment. Two stan- dards have been referenced in the Machinery Directive for 2011 to con- tinue 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 ele- ments of machine control systems, it omitted factors such as the use of elec- tronic controls, testing intervals, life cycles, and the probability of compo- nent 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 To remedy the situation, EN 954-1 has been replaced by 2006/42/EC which references the two standards, EN 13849-1 and EN 62061, covering a specific group of systems.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 sys- tems only. The standards extend proce- dures 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 capabil- ities and common cause failures. These additions to the Directive will create a framework that has to be fol- lowed for functional safety and related parts of control systems, with the focus being on common sense safety princi- ples, such as redundancy, diversity and fail safe behaviours. EN 13849-1 exam- ines complete ‘input/function/output’ safety functions, including all the com- ponents involved in their design. EN ISO 13849-1 goes beyond the qualita- tive 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 con- sidered as whole new machines and CE marked, and it is the legal responsi- bility 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 struc- tures 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.
An extract from the standard illustrates how calculation is applied to determine MTTFd (Mean Time to Dangerous failure) for components:
References
• B10 - Number of cycles, until 10 per cent of the components fails • B10d - Number of cycles, until 10 per cent of the components fail dangerously (may use B10d = 2 B10) • nop - The mean number of annual operations • MTTFd - Mean Time to Dangerous failure • hop - Mean number of operations, hours per day • With B10d and nop, the mean number of annual operations, MTTFd for components can be calculated as: MTTFd = B10d
0.1 x nop Indicator light for work cell illumination
anner has introduced the EZ-LIGHT WL50 Work Light, a compact and rugged general purpose indicator light designed for local illumination in areas with poor lighting conditions. Whether it is used in an industrial control cabinet, work cell, or other enclosure, the EZ-LIGHT WL50 Work Light provides proper task lighting with an even pattern of light and no shadows, reducing errors and eliminating the need for a flashlight.
B With an aesthetic shape that sheds debris and moisture, the WL50 is cased
in robust IP69K (standard) or IP67 (push-button models) housing to make it shock, vibration and impact resistant. A low-profile, flat-pack design and multi- ple mounting options make the WL50 both a simple and versatile indicator light. Turck Banner
T: 01268 578888
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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. A copy of Parker's guide to the Machinery Directive is available free from the website address below.
Parker Hannifin T: 01543 483824
www.parker.com/onepneumatic 29 Enter 324
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