Safety is one of the biggest and most important 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 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.
The key standard for safety of electrical equipment of machines in Europe and the UK is BS EN 60204-1:2018 – Safety of machinery. This standard is published by the International Electrotechnical Commission (IEC) and done so in parallel, with some specific 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 not limited to, enclosures, isolators, colour coding of actuators and documentation.
KEY CONDITIONS
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 enclosures should only be able to be opened under one of three conditions:
A key or tool must be used to open it Before it can be opened, live parts must be automatically disconnected 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°.
Electrical operating areas (e.g. switch rooms), 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 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.
SUPPLY ISSUES
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 equipment (Clause 5.5) instead of simply ‘devices for disconnecting…’. This is because while there has always been a distinction between ‘isolation’ and ‘disconnection’, it has not always been easily understood. This addition therefore helps with clarification. Isolation is a “procedure to securely disconnect and separate a machine from all hazardous energy sources” (source BS 14100).
Measures for protection against electric shock are also described. The measures are for protection against direct contact (basic protection) and for protection against indirect contact (fault protection). This is followed in the standard by measures for the protection of equipment. Equipotential bonding (earthing/grounding) is a basic provision for fault protection, so the standard also describes detailed requirements for protective conductors.
Control functions are the subject of clause 9 of the standard. Basic functions are included but there are also additional functions described. For example, clause 9.3.6 considers the ‘suspension of safety functions and/or protective measures’, with specific requirements for mode selection to deliver clarification and emphasis. This is important because selection of a different operating mode may have an impact on the risk. For example, when a guard interlock is bypassed to allow operation for maintenance or setting purposes.
Clause 10 of the standard includes colour coding and marking requirements for actuators. Also, unless otherwise agreed between the machine supplier and the user (the details of which is covered in Annex B of EN 60204-1), machine status indicator lights should be colour coded, with each colour identifying a specific status.
An example of the use of specific colours in Section 10.2 ‘Actuators’ is reserving the red/yellow colour combination for ‘emergency operation devices’. It also reserves the colour yellow ‘…for use in abnormal conditions, for example, in the event of an abnormal condition of the process, or to interrupt an automatic cycle.’
IS YOUR MACHINERY COMPLIANT?
Clause 17 of the standard outlines what technical documentation is required to demonstrate compliance. This includes 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 verification can be done at different stages throughout the design and development lifecycle process, even at the end of it, it would be better to do this as early as possible during design. As verification is intended to assure the conformity of a product, it is more cost-effective for faults to be identified and rectified during design, rather than waiting until the final machine is produced.
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 60204-1 requires that it must always include:
verification that the electrical equipment complies with its technical documentation in case of protection against indirect contact by automatic disconnection, conditions for protection by automatic disconnection shall be verified according to 18.2 functional tests EN 60204 often requires only a self-declaration against the conformance process. However, this does depend on the type of machine. For example, if EN 60204 was used for the presumption of conformity of an Annex IV machine, the electrical parts would still be included in the ‘special procedures’ required.
The complexity of EN 60204, coupled with the potential lethal consequences if electrical safety is incorrectly administered, means that compliance is not a process that machine users can afford to get wrong. However, the development of a practical checklist is a useful approach that will help ensure all relevant considerations have been covered.
OTHER REQUIREMENTS
Alongside the specifics of EN 60204, there are several global directives for electrical equipment and components with which machinery must comply.
The Low Voltage Directive (LVD) (2014/35/EU) ensures that electrical equipment falling within specific voltage ranges provides a high level of protection for European citizens and takes full advantage of the single market.
The Machinery Directive consists of a comprehensive set of health and safety regulations that machinery manufacturers must declare they have complied with to sell their products in the EU. For the UK market, the Supply of Machinery (Safety) Regulations 2008 continues to be in alignment with the EU’s Machinery Directive. These are closely linked and require compliance with the LVD (The Electrical Equipment (Safety) Regulations 2016 in the UK) and the ATEX Directive (UKEX in the UK). The latter of these regulates the requirements for equipment that is used in potentially explosive atmospheres. Alongside these, the EMC Directive (Electromagnetic Compatibility Regulations 2016 in the UK) aims to control electrical interference between different devices, and compliance with it is mandatory.
This means that all electrical equipment and machinery must be explicitly tested, certified or marked. With so many electrical components, it is vital to test electrical safety and ensure compliance with the complex array of relevant standards and regulations.