4 - Basic concepts

Last edit: 13/07/2023

Among the fundamental concepts addressed by the Standard, the following can be found:

  • Reference plane (§ 4.2)
  • Static and dynamic separation distance (§ 4.3)
  • Reaching out (§ 4.6)

Reference plane

The concept of a «reference plane» was introduced in EN ISO 13855 because in certain applications, proximity to machinery requires individuals to change their elevation to perform the intended activities, either by ascending or descending levels. Additionally, machinery design may allow individuals to change levels during access to the hazardous area or to reach a safety-related manual control.

In such cases, the reference plane, which manages the risk of reaching hazards, should be considered as the level that the person is utilizing for accessing those hazards. When there is a change in elevation (e.g., step, platform, machine frame), the reference plane should be determined according to Table 1 provided in the Standard.

Static and dynamic separation distance

Two different scenarios are considered:

  • Static separation distance: this is the separation distance determined up to the maximum boundary of the hazardous zone, regardless of the actual position of the hazard source within the physical limits of the machine or the position of the machine itself.
  • Dynamic separation distance: this is the separation distance determined from the boundary of the hazardous zone that the hazard source can reach based on its actual position and the change in this position during the total response time of the system T to achieve the required risk reduction.

Reaching out

The reaching distance has always referred to the distance between body parts and potentially reachable hazardous areas. The reaching distance concept in EN ISO 13855 is expanded to encompass the access to SRMCDs located within protected spaces. These SRMCDs, when activated, may introduce a new or increased risk to the operator. Therefore, the positioning and placement of such SRMCDs should be considered in order to ensure that they are not easily reachable by the operator when they are in a protected space.