Table of contents
- Machine safety
- Machinery Directive
- Emergency stop
- When is an emergency stop switch required?
- Which standards are emergency stop switches subject to?
- Signal towers
- What standards and guidelines are there for the use of signal towers and signal lights?
- When are signalling devices safety-relevant?
- What colours are there for signal towers and what is the meaning of the signal colours?
- Conclusion
Accidents at work are a regular occurrence. In addition to tripping, slipping and falling in the office or on the construction site, machines are also frequently involved. Ensuring occupational safety when working with machinery is therefore an ongoing issue, particularly in industry.
The safety of machines and systems and the fulfilment of standardised safety objectives must already be met in the design of machines. The strict legal and safety-related requirements for machine and system safety also push emergency stop switches and signalling technology to the forefront. This guide clarifies basic definitions and standardised safety rules for machines.
Definition of machine safety
Basic definitions on the subject of machine safety first include a precise understanding of the object machine: A machine is a technical structure that has been built for specific applications. Specifically, a machine consists of several connected and partially moving parts, as well as a drive system.
Throughout the entire life cycle of a machine, i.e. from the design phase onwards, aspects of machine safety must be observed in order to avoid hazards to people and the environment. The definition of machine safety therefore refers to explicit guidelines that make a machine safe from the moment it is placed on the market - and not just when it is professionally commissioned.
As soon as machines are placed on the market, requirements and standards must therefore be taken into account to ensure safety for the entire environment. DIN ISO 12100 serves as a guideline for machine safety, which describes a three-stage set of rules for achieving maximum machine safety.
The 2006/42/EC standard also regulates machine safety over the entire life cycle. However, the Machinery Directive, which is valid in Europe, provides the substance for this, ensuring that machines are designed in accordance with the defined principles and can therefore bear the CE mark, which is valid throughout Europe.
The Machinery Directive is also not limited to the regular operation of the design, but describes the entire life cycle from development to disposal. The 5 phases of machinery safety are closely related to this:
- Phase: Risk assessment: Determining the limits of the machine
- Phase: Safety planning: Identify potential hazards
- Phase: Assessing potential hazards
- Phase: Describe suitable risk minimisation measures
- Phase: Checking the effectiveness of implemented measures
Machinery Directive
The full definition of the Machinery Directive is known as: Directive 2006/42/EC of the European Parliament and of the Council of 17 May 2006 on machinery or in short: EC Machinery Directive (2006/42/EC).
It represents a standardised legal basis for the manufacture and placing on the market of machinery and applies to the entire European Economic Area.
It is also applied outside the EEA zone, for example to make products marketable in the EU. To this end, the EU regularly defines harmonised standards in accordance with the Machinery Directive in order to make machines mechanically and electrically safe for developers, sellers and operators.
What does the Machinery Directive regulate?
Machines that are handed over within the EU must comply with current safety standards and laws in accordance with the Machinery Directive, regardless of the country in which they are manufactured. Manufacturers therefore label their machines with the CE mark based on the Machinery Directive in order to provide easily accessible documentation that they fulfil all valid safety requirements for the movement of goods within the EU.
The very comprehensive Machinery Directive also lays down important principles and definitions for the standardised European marketing of machinery. Here are a few extracts:
What is a machine?
The Machinery Directive defines the following: Machinery is defined as all interconnected parts or devices with at least one moving part. This includes: Actuating elements, control and power circuits.
Machinery also includes
- The linking of machines, or combination of several machines and components
- Unfinished or incomplete machines
- Interchangeable equipment
- Safety components
- Lifting accessories
- Chains, ropes and belts as part of lifting gear or load handling attachments
- Detachable cardan shafts between a driving or towing machine and another machine
What is the difference between a system and a machine?
As a rule, a machine has a higher-level control system or a main control panel. Systems,on the other hand, are a complex combination of several machines and therefore also have several control consoles, but without an overarching control system.
What is the difference between an appliance and a machine?
The definition of an appliance as opposed to a machine is differentiated by the EU in that it describes an appliance as a finished apparatus for end users. An appliance also has electromagnetic interference, can cause it and thus impair its operation.
Emergency stop
One of the most important elements in connection with machine safety is the function of an emergency stop switch, which is positioned on a machine for immediate operability. Emergency stop switches must also be easily recognisable and consist of a red actuating element (switch) on a yellow background.
The slightly different meanings and definitions of emergency stop and emergency stop are explained in the following sections.
How often do emergency stop devices need to be checked for proper functioning?
Machines and systems require regular inspections, as does their safety technology. However, in order to answer the question of an exact test interval for emergency stop and emergency stop devices, the Ordinance on Safety and Health Protection in the Use of Work Equipment (Betriebssicherheitsverordnung - BetrSichV) defines a legal framework and states that the type, scope and deadline must be determined on the basis of a risk assessment. DIN VDE 0105-100/A1 Operation of electrical installations also provides some requirements. It includes regulations for periodic inspections of electrical systems and stationary equipment.
Difference between emergency stop and emergency stop
The two very similar terms and their use are based on a somewhat unsuccessful attempt to translate the English technical term "emergency stop", as well as the different use in the old and new Machinery Directive.
Emergency stop or emergency stop?
In order to distinguish in practice exactly what is meant by at least the first two terms emergency stop and emergency stop, the following simplified basic definition can be used:
- The emergency stop switch function interrupts the power supply to avert primary hazards caused by electrical current or voltages. (= switching off)
- The function of an emergency stop switch brings a machine to a standstill which, in other words, immediately stops the machine and its movements. (= stopping)
The harmonised European standard DIN VDE 0113-1 Machine testing/Safety of machinery also provides a complex explanation of the functional differences between emergency stop and emergency stop.
However, the exact distinction between the term emergency stop is completely unclear. On the one hand, the term is often used synonymously for emergency stop and emergency stop, but on the other hand it is often used as a generic term and therefore causes further confusion. However, in order to resolve the problem of terminology and its meaning, the Machinery Directive 2006/42/EC and 2009/127/EC as well as ISO standard 13850 now use the term emergency stop as a standardised term, as this also supports a higher level of safety.
In this context, the counteraction after an emergency stop is also important. This is done by acknowledging an emergency stop or stop command after it has been triggered. In accordance with DIN EN ISO-13849-1, this action is also referred to as a manual reset or manual reset function.
When is an emergency stop switch required?
According to the Machinery Directive, every machine and system must be equipped with at least one emergency stop function. The emergency stop switch must be quickly accessible and correctly labelled in order to bring the machine to an immediate stop.
The harmonised standards EN 60204-1 and EN ISO 13850 also specify when an emergency stop switch is required on a machine and possible exceptions for hand-guided work equipment. Among other things, the regulation is intended to ensure that hazardous movements of a machine are minimised once the emergency stop device has been activated.
Which standards are emergency stop switches subject to?
In order to prevent serious injuries or even save lives in hazardous situations, several regulations on emergency stop and emergency stop are applied in accordance with the Machinery Directive. In addition to the Machinery Directive, the following international standards also define design criteria for emergency stop and emergency stop and specify when which form of stop is to be applied.
- EN ISO 13850: DIN EN ISO 13850 deals with the safety of machinery, the emergency stop device and associated design principles. The European standard primarily specifies the requirements of the EC Machinery Directive 98/37/EC on emergency stops for machinery first placed on the market in the EEA.
- EN 60204: The standard DIN EN 60204 (VDE 0113-1) covers the safety of machinery and the electrical equipment of machinery. It also contains important installation standards for manufacturers. This also includes the specification of the stop functions and definition of the specific emergency stop categories or emergency stop categories.
- Stop function according to DIN EN 60204 (VDE 0113-1): Emergency stop category 0: A machine is stopped by switching off - the power supply is interrupted. Note the uncontrolled shutdown, where final machine movements are still possible.
Emergency stop category 1: A machine is forced to a controlled stop. The energy supply is maintained and only switched off when all machine movements have come to a stop.
Emergency stop category 2: In this category, a machine is brought to a controlled stop, the energy supply is not switched to off, but remains on.
In addition, the following emergency stop provisions apply: An emergency stop must function as a category 0 or category 1 stop. In addition, category 0 may only be used for hard-wired, electromechanical components. Furthermore, it must not be triggered by a switching logic. In the case of stop category 1 for emergency stops, the final interruption of the energy supply must also be ensured by electromechanical components. Important: The specific category to be applied must be based on an individual risk assessment of the machine! - DIN EN 418: The withdrawn standard DIN EN 418 dealt with the safety of machinery, emergency stop devices and functional aspects and design principles. The standard will be replaced by DIN EN ISO 13850.
Signal towers
Signal towers and signal lights provide clear signalling of the operating status of machines and systems. For example, the illumination with the colour red signals the active emergency stop status of a system. Signal lights are also used in industry to indicate production indicators. Machine traffic lights therefore not only signal the status of a system, but also reduce possible waiting times to optimise production processes.
Where are signal towers used?
Signal towers are primarily used in industrial environments and are to be understood as safety equipment for machines and systems. Their main task is to warn the machine user of possible dangers, to indicate the operating status and to signal industrial processes. Signal towers are therefore also used as optical controllers in automated processes.
What standards and directives are there for the use of signal towers and signal lights?
Signal towers and signal lights are part of safety-related signalling technology and are therefore defined in the European Machinery Directive 2006/42/EC. EN ISO 13849-1 Safety of machinery - Safety-related parts of control systems - Part 1 also regulates the standardisation of relevant components.
When are signalling devices relevant to safety?
Whether signalling devices are safety-relevant must be determined as part of the risk analysis prescribed by the Machinery Directive. The content of the analysis is to find out what risks a machine harbours and what precautions must be taken to avert these risks.
What needs to be considered when using signal towers
Signal towers have lights in different colours to indicate different machine statuses. Signal lights are also known as status lights and are subject to the EN ISO 13849-1 standard.
Each light or signal colour is assigned an exact meaning. This has the advantage that the status indicators can be transferred to different machines and interpreted identically.
What colours are available for signal towers and what is the meaning of the signal colours?
The lights on signal towers have an assigned colour depending on their meaning. The more varied the information requirements of a machine traffic light, the higher the number of signal colours attached to the column. The following table provides information on signal colours and their meaning:
| Colour | Meaning | Explanation in detail |
|---|---|---|
| Red | Dangerous condition | What the red colour means can usually be answered intuitively. Red indicates the highest warning level of a signal tower. There is a high risk of electrical voltage or moving machine parts. Immediate action is required by stopping the machine in a controlled manner or disconnecting it from the power supply. |
| Yellow / orange | (Imminent) critical condition | The colours yellow or orange warn of an imminent, critical condition This can indicate an overload or an imminent critical exceedance In this case, monitoring or intervention is required. |
| Blue | Dedicated (manual) action required | What the colour blue stands for cannot be uniformly defined. On the other hand, the meaning of the blue light can even be defined individually. For example, when the blue signal section lights up, an action by the operator may be required or it may completely indicate the changeover of a machine to manual operation. However, the individual meaning must clearly differ from the main signal colours red, yellow or orange and green already mentioned. |
| Green | Safe condition | The colour green indicates the normal, typical condition of a machine. The meaning also includes that a system is ready for operation. |
| White | Individual meaning | White or clear light on a signal light also has no standardised meaning. The exact meaning of the colour must therefore be determined on an application-specific basis. The colour white or the clear light is often used to indicate that a machine is energised. |
Conclusion
Conspicuous emergency command devices using emergency stop buttons or signal towers that provide information about the status of a machine are essential elements that contribute to safety in industry. After all, the incorrect behaviour of an industrial system can endanger people and even cost lives. In this guide, we have looked at relevant definitions and legal standards for machine safety. These can be used to recognise, assess and prevent safety gaps in machinery and thus ensure a safe working environment.
Despite careful editing and checking of the content, Stecker Express assumes no liability for the topicality, correctness, completeness and quality of the information provided.
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