EN ISO 13855, “Safety of machinery – Positioning of safeguards with respect to the approach speeds of parts of the human body (ISO 13855:2010)”, gives the method for calculating how far a safeguard such as a light curtain must be placed from the hazard zone. The idea is simple: the machine must have stopped before a person can reach the hazard. The distance is calculated from the approach speed of the person and the overall stopping time of the machine.
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EN ISO 13855 at a glance
| Edition cited in the EU Official Journal | EN ISO 13855:2010 |
|---|---|
| Official title | Safety of machinery – Positioning of safeguards with respect to the approach speeds of parts of the human body (ISO 13855:2010) |
| Legislation supported | Machinery Directive 2006/42/EC; from 20 January 2027 Machinery Regulation (EU) 2023/1230 |
| Type of standard | Type B standard |
| Basic formula | S = (K × T) + C; S is the minimum distance, K the approach speed, T the overall stopping time, C an additional distance that depends on the detection capability of the device |
Which safeguards are covered?
The standard applies to the positioning of safeguards that protect by detecting a person or by keeping the hands occupied:
- Light curtains and light beams (electro-sensitive protective equipment)
- Laser area scanners
- Pressure-sensitive mats and floors
- Two-hand control devices
- Interlocking movable guards without guard locking
Distances against reaching over fixed guards or through openings belong to EN ISO 13857, not to this standard.
Main requirements of the standard
- Overall stopping time (T): The response time of the safeguard plus the stopping time of the machine, including delays in the control system.
- Approach speed (K): For approach at right angles to the detection zone, 2,000 mm/s is used for hand speed and 1,600 mm/s for walking speed.
- Additional distance (C): It covers how far a body part can intrude before it is detected; for light curtains with a detection capability up to 40 mm, C = 8 × (d − 14) mm.
- Coarser devices: With a detection capability between 40 mm and 70 mm, the approach speed is 1,600 mm/s and the additional distance is 850 mm.
- Two-hand control: The distance from the buttons to the hazard zone must allow the machine to stop after the hands are released.
- Interlocking guards: Without guard locking, the guard opening must be far enough away for the movement to stop before a person can reach in.
The calculation starts with 2,000 mm/s; if the result is more than 500 mm, it may be repeated with 1,600 mm/s.
EN ISO 13855 verification and measurements
The key input is the stopping time, which is measured on the machine.
| Test or check | What is verified? |
|---|---|
| Stopping time measurement | Time from the stop signal to the end of the hazardous movement |
| Minimum distance calculation | The formula is applied with the factors that match the approach direction and detection capability |
| Measurement of the installed position | The actual position of the device on the machine meets the calculated distance |
| Check for reaching around and standing behind | The hazard zone cannot be reached over, under, around or from behind the detection zone |
Brake wear can lengthen the stopping time. The measurement is therefore recorded and repeated after any change that affects braking.
Its place in the CE marking process
- Risk assessment: The hazard zones to be protected by a safeguard are identified under EN ISO 12100.
- Design: The device type and detection capability are chosen and the minimum distance is calculated to EN ISO 13855.
- Verification: The stopping time is measured and the position of the device is checked on the machine.
- Technical file: The distance calculation and the stopping time report go into the technical file.
- Declaration of conformity: EN ISO 13855 is listed among the standards applied.
Conformity with a harmonised standard gives presumption of conformity with the relevant essential requirements of the machinery legislation. Turkey applies the same rules through its own regulation aligned with 2006/42/EC. See also CE marking of machinery.
Standards applied together
- EN ISO 13857: Safety distances for upper and lower limbs
- EN ISO 14119: Interlocking devices associated with guards
- EN ISO 13851: Two-hand control devices
- EN ISO 13849-1: Performance level of the safety function connected to the safeguard
Frequently asked questions
How far from the machine should a light curtain be?
There is no fixed value. The distance is calculated for each machine from its measured stopping time and the detection capability of the light curtain.
What if the distance is not available?
A device with finer resolution can be chosen, the stopping time can be shortened, or a movable guard with guard locking can be used instead.
Which edition applies?
The edition cited in the EU Official Journal is EN ISO 13855:2010. A newer edition has been published by CEN; for presumption of conformity the edition cited in the Official Journal is the one that counts. Check the current citation before testing starts.
Other standards in this group
- EN ISO 13849-2: Validation of Safety-Related Control Systems
- EN ISO 13850: Emergency Stop Function
- EN ISO 13857: Safety Distances
- EN ISO 14119: Interlocking Devices for Guards
