Guidelines to improve machinery safetyFesto is launching a new safety guideline to assist designers to improve the safety of their machines and aid them in meeting the requirements of the latest Machinery Directive. The guidelines group commonly required safety functions and provide off the page 'black box' solutions. These include individual safety products and sub-systems along with the required information and data for popular software documentation packages for both pneumatic and electric drives.
Safety management of a machine design starts with the risk analysis and assessment; once the risks have been identified various measures can be taken to reduce these include design measures aimed at reducing the hazards, technical measures (which the Festo safety guidelines address) and then the more people oriented, softer elements of training, signage, warnings etc.
In technical wording terms, to comply with the Machinery Directive, designers incorporating safety-related control systems are seeking a presumption of conformity. More commonly, they can demonstrate they have met their obligations and protect themselves and their company through the use of the relevant standards such as EN ISO 13849, ISO 14121, IEC 62061 or IEC 61508. A commonly asked question of our technical specialists is "when to use which standard...", and whilst there are more complex reasons for electing to use one rather than another, there is a clear distinction for mechanical systems. ISO 13849 specifically refers to systems where wear needs to be considered, such as usage rates have an effect upon the safety of components within the system.
For example a pneumatic valve which is operated 300 times an hour will have a different life and reliability compared to one operated once a day. High frequency usage or infrequent use both have a potential impact upon a pneumatic valve used in a safety circuit. Diagnostics, monitoring and ultimately built in redundancy will all play a part in increasing the reliability of the system.
When a safety component is a complex part in its own right, designers require a lot more data to enable them to determine the reliability of their solution. This data has to be derived by the manufacturer by thorough tests, calculations and analysis. Testing a statistically sound batch of components enables Festo to determine the probability of a part failing within that life time and analysing whether the mode of failure is critical to the safety function. This is expressed as a life time that 90% of components are predicted to reach without failure. Combining this figure with the expected duty cycle (number of actuations per year) derives a Mean Time To Failure, another part of the safety jigsaw.
Festo's approach is to offer standard solutions based on the most commonly required functions. Reducing technical measures to just seven pneumatic and seven electrical drive functions makes it considerably easier for designers to select the components and systems they need in the form of components, circuits and engineering.
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