MAINTENANCE MANAGEMENT FEATURE
WHAT ARE THE REQUIREMENTS for machinery electrical safety?
Electricians responsible for maintaining machinery are often trained to BS 7671 which largely excludes machinery. Neil Dyson discusses how best to approach electrical safety/maintenance
T
he key standard for machinery electrical safety is EN 60204-1:2006
+A1:2009 Safety of machinery - electrical equipment of machines – general requirements. However, many electricians responsible for maintaining machinery on site are only being trained to BS 7671 – Requirements for electrical installations. This standard is only applicable in the UK and applies to low voltage electrical installations covering general wiring of buildings. In Part 3.35 of EN 60204 machinery is defined as: “an assembly of linked parts or components, at least one of which moves, with the appropriate machine actuators, control and power circuits, joined together for a specific application, in particular for the processing, treatment, moving or packaging of a material. The term ‘machinery’ also covers an assembly of machines which, in order to achieve the same end, are arranged and controlled so that they function as an integral whole”.
ISOLATOR SWITCHES An isolator switch will electrically isolate the connected circuits to stop an unsafe machine working. EN 60204 requires all isolators to be lockable, attached to the machine and capable of disconnecting all electrical supplies. If this isn’t possible circuits must satisfy further specific requirements which are outlined in detail within the standard.
ENCLOSURES
The standard requires that electrically live parts be located inside enclosures to
provide protection against a human having direct contact with them. Any enclosures should only be able to be opened under one of three conditions: 1. A key or tool must be used. 2. Before it can be opened live parts must be automatically disconnected eg by interlocking the enclosure door with a disconnecting device. 3. If opening with a key or disconnection device is not possible opening should only be allowed when all live parts are protected against direct contact to at least IP2X or IPXXB (see standard IEC 60529) which requires that an exposed terminal cannot be touched. It is recommended that enclosure doors are no wider than 0,9 m and have vertical hinges with an opening angle of at least 95 degrees. Any large-scale enclosures which allow a person to fully enter machinery such as palletisers must provide a means of escape such as panic bolts on the inside of doors.
COLOUR CODING AND DOCUMENTATION Part 10 of EN 60204 includes colour coding and marking requirements for push-button actuators. Under no circumstances should the colour red be used as this is reserved for emergency stop and switching-off actuators. Unless otherwise agreed between
machine supplier and user (Annex B of EN 60204) machine status indicator lights must be colour coded with each identifying a specific status. Section 17 outlines the technical documentation required to prove
LACK OF MAINTENANCE RESOURCE IMPACTS PRODUCTIVITY
Maintenance budget constraints are having a significant impact on machinery uptime, according to Bosch Rexroth. A recent survey conducted by the drives and controls specialist in conjunction with IET reveals that the maintenance budgets of more than 50% of manufacturers had stagnated or reduced over the past five years despite the fact that more than two thirds stated that the breadth of equipment they maintain has increased and three quarters advising that it utilised is far more complex compared to five years ago. “There are outstanding examples of maintenance
practice in UK industry”, says UK service manager Richard Chamberlain. “However, MRO is often
perceived to be a cost not an investment or potential profit driver. The majority of maintenance budgets are stagnant or have been cut but we are asking for more and more from our maintenance teams as the complexity of technologies increases rapidly. As such we need a higher level of skills, not just in operations but in maintenance and training. “Better communication and understanding of the
benefits of proactive maintenance in finance departments and procurement will go a long way to ensuring British manufacturing remains competitive on the world stage.”
www.boschrexroth.co.uk/UKmaintenancereport / FACTORYEQUIPMENT
compliance including information relating to a machine’s electrical installation, operation and maintenance which can be in the form of drawings, diagrams, charts, tables and instructions. While the standard recognises that different levels of detail will be needed according to the complexity of the machinery there are particular requirements relevant to all.
VERIFICATION
The verification process is intended to ensure that a product meets the specified requirements of EN 60204. This can be carried out either at different stages throughout the design and development lifecycle process or at the end of it. The extent of the verification that is required is made clear in the specific product standard that relates to each different type of machine. However, where there is no such dedicated standard EN 60204 requires
that it must always include: l verification that the electrical equipment complies with its technical
documentation; l in the case of protection against indirect contact by automatic disconnection, conditions shall be
verified according to 18.2; l functional tests.
UNDERSTANDING COMPLEXITY While is EN 60204-1:2006 +A1:2009 is complex the development of a practical checklist will help ensure that all relevant considerations are covered; the one we use runs to 27 pages. EN 60204A requires only a self-
declaration against the conformance process; its complexity coupled with the potential lethal consequences if electrical safety is incorrectly administered means that it is a process that machine users cannot afford to get wrong. Safety is one of the most significant issues facing the machinery industry in Europe today and the electrical element is an essential consideration for keeping machine operators and maintenance personnel safe.
TÜV SÜD Product Service T: 01489 558100
www.tuv-sud.co.uk
FACTORY EQUIPMENT | FEBRUARY 2016 15
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