4 - Selection of protective measures

Last edit: 26/06/2023

4.2.1 Suitablity of protective equipment
Protective equipment is typically selected when machine operation requires frequent access, personnel interaction with the machine, good visibility of the machine or process, or when it is difficult to provide fixed guarding. Some characteristics of particular machines can preclude the use of protective equipment as the sole protective measure. Examples are:
a) Possibility that the machinery will eject materials
b) Risk of injury from thermal
c) Unacceptable noise levels
d) An environment likely to adversely affect the function of the protective equipment
e) A material being processed that can influence the effectiveness of the protective measure.

4.4 Uses of protective equipment
A protective equipment may be used to provide:
a) Trip function; or
b) Presence sensing function; or
c) Combination trip function and presence sensing function

4.4.2 Trip function
Where the protective equipment is used to provide a trip function, it shall be positioned at a sufficient distance from the specific machine hazard to ensure the machine can stop or otherwise reach a safe condition before a person can reach the hazard zone. The minimum distance shall be maintained for all foreseeable directions of approach.
This distance shall take into account:
a) Protective equipment detection capability in relation to human characteristics
b) The overall system stopping performance
c) In the case of moving parts of machines than can reduce the separation distance, the minimum distance shall apply from the furthest extension of the moving parts towards the direction of approach. Positioning of protective equipment or detection zone
The positioning of protective equipment or detection zone shall be in accordance with ISO 13855.
Where an initial calculation of the minimum distance gives a result that cannot be accommodated, the following can assist in achieving an adequate stopping performance in order to meet the requirements of ISO 13855:
a) Selection of protective equipment with a better detection capability or faster response time
b) Reduction of the overall stopping time (t2)
c) Reduction of the overall system response time (t1)
d) Using a different configuration of approach to reduce intrusion towards the hazard Supplementary protective measures
Supplementary protective measures can include:
– Barriers to ensure that a person cannot approach the machine hazard from directions not protected by the protective equipment
– Provision of a restart interlock
– Provision of a presence sensing device
– Measures to prevent a person being present between the protective equipment and the hazardous zone
If additional measures are used to prevent a person being present between the protective equipment and the hazardous zone, and if the additional measures are designed to be removable, then they shall be interlocked with the safety-related control system so that hazardous machine movements is not possible if the additional measures are not present.

4.4.3 Presence sensing function
Where the protective equipment is used to provide a presence sensing function, the machine shall remain in a non-hazardous state when a person or part of a person is present in the detection zone.
Supplementary measures shall be provided as necessary to ensure that the detection zone cannot be circumvented.

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