Minimum clearance to prevent crushing is a critical technical measure in the safe design of machinery. In industrial environments, many accidents could be avoided if designers and manufacturers adhered to the essential requirements of the Machinery Directive (2006/42/EC) and the Machinery Regulation. One fundamental approach to achieving high safety levels is eliminating the risk of crushing by ensuring adequate distances between moving parts of a machine or between a moving and a stationary part. The ISO 13854 standard (formerly EN 349) outlines methods for determining these clearances and protecting the human body from crushing risks. Below, we discuss ten key aspects of this standard, from the significance of these clearances and their values to the benefits of adapting machine designs to these guidelines.
Table of Contents
1. The Importance of Minimum Clearance to Prevent Crushing
Before embarking on machine design or the development of a machinery assembly, it is crucial to identify all zones where accidents, such as crushing of an operator or another person, could occur. Crushing zones exist where two elements (either both moving or one moving and one stationary) can come dangerously close to each other.
The principle is straightforward: if, during normal operation (as well as during maintenance or startup activities), human body parts can enter an area where the distance decreases, the risk must be mitigated at the design level. Minimum clearance to prevent crushing serves as a universal technical measure that neutralizes the risk even before the need to install guards or interlocks arises.
2. Fundamentals of ISO 13854 Standard
The ISO 13854:2019 standard specifies requirements related to preventing human body crushing by moving machine parts. It describes detailed clearance values that must be maintained to ensure sufficient clearance. In practice, by applying this standard, designers can ensure they are considering the best available anthropometric data.
Currently, ISO 13854 is a harmonized standard with the Machinery Directive, meaning its application provides the machine manufacturer with the so-called “presumption of conformity” with relevant safety regulations. For many industries—from food processing to automotive and heavy industry—this is crucial as it significantly simplifies the conformity assessment process and CE marking.
3. Application in the Context of the Machinery Directive and Regulation
The essential requirements of the Machinery Directive 2006/42/EC and the Machinery Regulation focus on eliminating risks at the source. This philosophy aims to minimize or eliminate hazards at the design stage of the equipment.
Regarding the risk of crushing, minimum clearance to prevent crushing acts as a technical measure. Incorporating these clearances into the machine design reduces the number of potentially hazardous points (e.g., contact points of moving parts) and minimizes the need for additional protective measures against crushing through various guards. In practice, however, the ISO 13854 standard is often combined with other standards, such as EN ISO 13857, which addresses distances preventing access to hazardous zones.
4. Minimum Clearance to Prevent Crushing and Essential Requirements
From a machine manufacturer’s perspective, the most important aspect is to demonstrate, in the event of an inspection or audit, that the risk of crushing has been properly analyzed and reduced. The Machinery Directive requires that all mechanical hazards (including those causing injuries due to crushing) be identified and minimized.
When designing machines in accordance with ISO 13854, it is not sufficient to “eyeball” certain values. Designers must strictly adhere to the numerical data contained in the standard (e.g., minimum clearances for fingers, hands, feet, or heads). Applying the correct values ensures compliance with essential health and safety protection requirements.
5. Identifying Hazard Zones and Technical Measures
To practically apply minimum clearance to prevent crushing, it is necessary to accurately identify zones where the risk of such an event exists. This involves conducting a risk assessment based on the guidelines of ISO 12100 and then locating all points where two surfaces could come into close proximity.
After identifying hazards, it is essential to determine which body part (finger, hand, entire limb, head) could be caught in the gap. The appropriate minimum clearance value from the ISO 13854 tables is then selected. In some cases, leaving a 25 mm gap between moving parts is sufficient (enough to prevent finger crushing), while in others, 100 mm (for hand protection) or even 500 mm (for full torso protection) may be necessary.
6. Designing Machinery Assemblies with Minimum Clearance to Prevent Crushing
In industrial practice, machines often operate in production lines where one device is connected to another. Such a machinery assembly can create additional crushing zones, such as between the edges of two adjacent machines.
Designers must ensure that no dangerous gaps arise at the contact point or during the movement of one of the machines. This often requires maintaining adequate clearance between devices on the production line. If, for various reasons (spatial constraints, process requirements), the values specified by the standard cannot be achieved, additional guards or interlocks must be introduced.
7. Anthropometric Data
The “minimum clearance to prevent crushing” values are based on extensive anthropometric research. The standard considers typical adult human body dimensions, such as finger thickness, hand circumference, head diameter, and foot height with footwear.
By adopting specific values, ISO 13854 ensures that maintaining these clearances prevents the human body (in its most vulnerable areas) from being crushed. This provides machine manufacturers with a solid foundation to demonstrate that the design eliminates the risk of crushing in a scientifically justified manner.
Additionally, the standard emphasizes that factors such as work clothing or tools worn on the body should not be overlooked. These can increase the effective thickness or circumference of a limb, and designers must consider whether the standard clearance value remains sufficient.
Note!
If a machine designer, during the risk analysis stage in accordance with ISO 12100 (design assumptions section), determines that individuals who do not fit the standard population may work with the machine, this must be considered a risk!
8. Practical Examples of Minimum Clearance to Prevent Crushing
- Presses and Actuators: If a press descends over a workpiece, it can leave a gap of 30–50 mm in the final position, protecting the operator’s fingers from complete crushing. In industrial applications, guards are often required, but the clearance itself can serve as an additional safeguard.
- Conveying Equipment: In production lines where conveyors meet machines, designers must ensure that body parts cannot become trapped between the belt and the drive drum. If the minimum distance is less than the values specified in the standard, a design modification or the installation of special protective covers will be necessary.
- Industrial Robots: If a robot arm moves near a fixed structure, it is essential to check whether a person could be caught between the robot and the wall. If so, at least 500 mm of clearance should be provided to avoid crushing the entire torso.
- Milling Machine Work Table: This example pertains to ready-made machines often installed by the user. If the milling machine’s table is movable and positioned close to a wall, it can cause crushing for someone who finds themselves in such a zone. The milling machine manufacturer should indicate this risk in the original instructions and inform about the correct placement of the machine concerning the crushing zone.
9. Design Errors and Legal Consequences
Ignoring the guidelines of ISO 13854 can lead to non-compliance with the essential requirements of the Machinery Directive. If an accident involving the machine occurs and it is found that the manufacturer did not ensure compliance with the standards, they face significant financial and legal consequences.
Moreover, machine buyers—aware of their rights and obligations—are increasingly demanding full technical documentation from equipment suppliers, confirming that “minimum clearance to prevent crushing” has been considered. This is not only a matter of safety but also of building trust and credibility in the market.
10. Minimum Clearance to Prevent Crushing – Summary of Benefits
Applying the ISO 13854 standard and designing with minimum clearance to prevent crushing translates into tangible benefits:
- Compliance with the Machinery Directive: The machine design meets essential requirements, significantly facilitating the conformity assessment procedure and CE marking.
- Reduced Risk of Accidents: Mechanical collisions and crush injuries are among the most serious hazards in machine operation. Proper clearances at critical points reduce the number of incidents.
- Improved Ergonomics: Often, sufficiently large gaps allow workers to perform maintenance and operations more freely without compromising safety.
- Protection of Manufacturer’s Reputation: Companies investing in machine safety build a better reputation among customers and partners, avoiding fines and costly legal proceedings.
- Durability of Solutions: If a machine is designed according to the latest knowledge and standards, there is no need for costly safety modifications later on.
Designing machines with the principles of ISO 13854 in mind is becoming standard practice in an increasing number of industrial facilities. Thanks to the consistent anthropometric values recorded in the standard, every designer can uniformly determine what gap will prevent the crushing of a finger, hand, limb, or entire body.
Minimum clearance to prevent crushing thus forms the foundation of safe equipment design, and its proper implementation plays a crucial role in protecting the health and lives of workers. From the perspective of machine manufacturers and users, it is an investment that not only meets formal requirements but also translates into real safety in everyday operations.
FAQ:
It refers to safe distances between moving parts of machines, protecting humans from injuries caused by crushing.
Minimum clearance is defined by the ISO 13854 standard (formerly EN 349), compliant with the Machinery Directive 2006/42/EC.
Because its application is required by law, it protects machine users and helps avoid liability for accidents.
You need to analyze areas where moving machine parts can come into contact with the human body and apply appropriate protective measures.
Design errors related to clearances can result in legal consequences, especially in the event of workplace accidents.