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ELECTRICAL SAFETY
HOW ELECTRICALLY SAFE IS YOUR MACHINERY?
set of rules and precautions that protect against potential electrical hazards. The regulations are designed to guard against electrical risks such as arcing and electric shocks. Due to the enormous influence that electrical components have on the reliability and quality of a product, machinery and processing equipment must meet several legal safety criteria. Following the UK’s exit from the European Union (EU), the actual process required for manufacturing compliant products has not changed from a legal perspective. As the EU Directives are transposed into National Law, the UK already has a legal system in place that applies. EU harmonised standards have therefore simply been carried across as UK designated standards in order to maintain a single model.
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The key standard for safety of electrical equipment of machines in Europe and the UK is BS EN 60204-1:2018 - Safety of machinery. Electrical equipment of machines. General requirements. This is published by the International Electrotechnical Commission (IEC) and published in parallel, with some changes, by CENELEC (European Committee for Electrotechnical Standardization). The machinery industry has been using this standard for many years, however it is somewhat complex. I have highlighted a few key aspects below.
The standard applies to electrical, electronic and programmable electronic equipment and systems to machines not portable by hand while working, including a group of machines working together in a co- ordinated manner. It therefore provides requirements and recommendations relating to the electrical equipment of machines which includes, but is not limited to, enclosures, isolators, colour coding of actuators and documentation.
The standard requires that electrical live parts be located inside enclosures or suitably insulated to provide protection against a human having direct contact with them. Any
afety is one of the most significant issues facing machinery owners today, and the electrical element is an essential
consideration for keeping machine operators and maintenance personnel safe. Electrical safety is a
By Stewart Robinson MIET MInstMC, principal engineer and functional safety expert at TÜV SÜD
enclosures should only be able to be opened under one of three conditions:
1. A key or tool must be used to open it.
2. Before it can be opened, live parts must be automatically disconnected.
3. Opening without the use of a key or a tool and without disconnection of live parts shall only be possible when all live parts are protected against direct contact to at least IP2X or IPXXB (see standard IEC 60529).
It is recommended that enclosure doors are no wider than 0.9m and have vertical hinges that have an opening angle of at least 95 degrees.
Electrical operating areas (e.g. switchrooms), which allow a person to fully enter, must be provided with means to allow escape. Doors for such areas, must have a clear width of at least 0.7m and a clear height of at least 2.0m. In cases where equipment is likely to be live during access and conducting parts are exposed, the clear width shall be at least 1m. In cases where such parts are present on both sides of the access way, the clear width shall be at least 1.5m.
The normative requirements for Electromagnetic Compatibility (EMC) is given without much detail. However, a detailed informative Annex H is included, which should be helpful to machine builders because it
28 SPRING 2024 | INDUSTRIAL COMPLIANCE
describes practical measures that can be used to reduce the effects of electromagnetic influences. Detailed guidance is also contained in specific EMC standards e.g. the IEC 61000-6 series.
The requirements for a ‘supply disconnecting device’ (an isolator) are described. An isolator is a manually actuated control device used to switch off the supply of electrical energy to all or a part of an installation where a risk of electric shock or another risk is involved. An isolator must be provided for disconnection of each incoming supply, and for each on-board power supply. The standard also allows for the operating means for a supply disconnecting device, that is not intended for emergency operations, to have a supplementary cover or door for protection against environmental conditions. This is because if the operating means (the handle) of an isolator is exposed, it could suffer from degradation due to environmental conditions or have mechanical damage. The requirements relating to isolators are listed in Clause 5 of EN 60204.
The terminal for the external protective conductor must be in the same compartment as the incoming supply not simply “in the vicinity”. Also, for the breaking capacity of the supply disconnecting device, the calculation must consider motors supplied by inverters or similar devices (power drive systems). Supply disconnecting devices are also often provided for the purpose of isolating electrical
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