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EN ISO 13857: Does the guarding on the equipment meet the requirements?
Created on 03.07
EN ISO 13857 is a very important Type B1 general standard in the field of machinery safety. Its core purpose is to prevent upper and lower limbs from reaching the hazardous areas of machinery by specifying safety distances.
1. Scope and Basic Principles
- Applicable objects: Applicable to all types of machinery (industrial and non-industrial environments).
- Core concept: Safety protection is achieved through "distance." If the danger zone cannot be completely enclosed, a sufficient distance must be maintained so that limbs cannot reach the danger point even when extended to their limit.
2. Safety Distance Requirements for Upper Limbs
The standard divides upper limb protection into three main scenarios based on how limbs approach the danger zone and provides detailed table lookup data:
A. Reaching through openings
When there are openings in the protective device (e.g., mesh holes in a mesh fence, gaps in a railing, slots), the size of the opening determines the required safety distance.
- Principle: The smaller the opening, the shallower the depth an arm can reach into, thus requiring a smaller safety distance behind it; the larger the opening, the deeper an arm can reach, and the safety distance must be greater.
- Example key data (refer to standard tables):
- Application: Commonly used in the design of metal mesh fences and perforated plate guards.
B. Reaching around obstacles
When the protective device is not fully enclosed but exists as a barrier, and a person attempts to reach around the edge (side, top, or bottom) of the barrier.
- Principle: Depends on the height of the protective structure (hpshps) and the height of the hazardous zone (hh).
- Requirements:
- If the protective structure is sufficiently high (generally ≥1400mm) and the hazardous zone is located low, additional horizontal distance may not be required.
- If the protective structure is too low and personnel can easily reach over it, a larger horizontal safety distance (SR) is required.
- Table lookup factors: The distance is determined by consulting the table, considering the height of the protective structure, the height of the danger zone, and whether the reach is upwards, downwards, or horizontal.
C. Reaching over obstacles
This occurs when personnel attempt to reach into a danger zone behind a protective structure from above (e.g., reaching over a fence to touch a machine behind it).
- Principle: Depends on the height of the protective structure (hps) and the height of the hazardous area relative to the ground (hh).
- Key Rules:
- Protective structure height: Generally, a protective structure height of at least 1400mm is required to effectively prevent most people from climbing over. If it is less than 1000mm, it is usually considered ineffective against climbing over.
- Safety distance (SR): As the protective structure height decreases, or the hazardous zone height increases, the required safety distance increases sharply.
- Example: If the guardrail height is 1000mm and the hazardous zone is at ground level, a horizontal distance of over 2000mm may be required; if the hazardous zone is also high, the distance requirement will change.
- Special attention: For low-risk areas, standards allow for some relaxation, but this must be based on a risk assessment.
3. Safety distance requirements for lower limbs (Lower Limbs)
Lower limb protection mainly prevents people from kicking, stepping on, or climbing over the protective device to reach the hazardous zone (e.g., underground chains, low rotating shafts).
- Typical applications: Protective skirts at the bottom of machines, design of covers for trenches.
4. Key implementation steps
In practical design, EN ISO 13857 is usually followed through the following process:
- Identify hazardous zones: Determine the specific location (height, depth) of the machine's hazardous points (cutting, crushing, entanglement, etc.).
- Select protective type: Decide whether to use a guarded enclosure with holes (passing through), a fence (going around/over), or other forms.
- Determine geometric parameters: Measure or set the height of the protective structure, the size of openings, and the height of the hazardous zone.
- Determine distance from tables: Based on the above parameters, find the corresponding minimum safety distance (SRSR) in the relevant tables of the standard (Table 1~Table 6, etc.).
- Verification and adjustment: Ensure that the actual designed distance is greater than or equal to the value obtained from the tables. If space is insufficient, the protective structure height must be increased or the opening size reduced.
5. Relationship with other standards
- ISO 12100: EN ISO 13857 is developed based on the risk assessment principles of ISO 12100. A risk assessment should be performed before using this standard.
- ISO 14120: Specifies the design and manufacturing requirements for guards, while ISO 13857 specifies the position (distance) where these guards should be installed. The two are often used together.
- ISO 13855: If the guard has safety functions (e.g., light curtains, sensing mats), the calculation of its safety distance must follow ISO 13855 (considering machine stopping time), not ISO 13857. ISO 13857 is only applicable to fixed physical guards.
Summary
EN ISO 13857:2019 is the "ruler" for mechanical guarding design. It doesn't tell you how to build guards, but it clearly states how far guards should be from hazardous points and how large openings in guards can be. The key to compliance lies in: accurately measuring geometric dimensions -> correctly selecting tables -> strictly implementing the minimum distances derived from the tables. Any design with distances less than those specified by the standard is considered non-compliant with safety requirements, unless compensated by other equivalent measures (e.g., interlocking devices).