Standards / Machinery Safety
EN ISO 13850
Machinery Safety
Current
Emergency Stop Function
EN ISO 13850 is the European standard for the emergency stop function on machinery. It sets out what the function must achieve, how the actuating devices must look and behave, and — importantly — establishes that emergency stop is a complementary protective measure rather than a substitute for safeguarding.
Scope
EN ISO 13850 applies to the emergency stop function on all machinery, covering the design principles for the function, the requirements for actuators including their appearance and latching behaviour, the reset arrangement, and the relationship between emergency stop and the machine control system.
Exclusions & Related Standards
- Emergency stop is not a safeguard and does not replace guards under EN ISO 14120 or interlocks under EN ISO 14119.
- Emergency stop is not isolation and does not make a machine safe to work on.
- The reliability required of the function is determined under ISO 13849.
- The overall framework is ISO 12100.
Key Requirements & Marking
The actuator must be immediately recognisable and readily accessible, conventionally a red mushroom-head device on a yellow background, and it must latch when operated so that it has to be reset by hand at the device. Resetting must not by itself restart the machine. Devices must be positioned so that one is reachable from every place a person may need it, and the function must take priority over all other machine functions.
It latches so it must be released at the device, and releasing it does not restart the machine.
Testing Overview
Assessment covers the response of the function from actuation to the machine reaching a stopped state, the latching and reset behaviour of the actuator, the priority of the function over other commands, the mechanical endurance of the device, and confirmation that reset alone does not restart the machine.
Selection Guide
Provide devices at every operator position and along extended machines, using pull cords where a run has to be covered continuously. Assess reachability from the positions people actually occupy, including those used during setting and clearing rather than only the normal operating station. Do not use emergency stop as the means of making a machine safe for intervention.
Inspection, Care and Maintenance
- Test each device on a defined schedule, since normal running never exercises the function
- Keep devices unobstructed and free of stored material, which is the most common practical failure
- Confirm that reset does not restart the machine after any control system modification
- Replace damaged or sticking actuators rather than leaving them in service
- Include every device in the test record, as an untested device is an assumption rather than a control
The most common practical failure is not a faulty device but one that cannot be reached.
Frequently asked questions
Does emergency stop make a machine safe to work on?
No. It stops the machine but does not isolate it. Stored pneumatic, hydraulic, electrical, gravitational and rotational energy all remain, so intervention still requires isolation.
Why must an emergency stop latch?
So that it has to be reset by hand at the device, which means going to the place where the problem occurred before the machine can run again. Resetting must not itself restart it.
Can an emergency stop count as the safeguard for a hazard?
No. It is a complementary protective measure that depends on a person recognising danger and reacting, which is not reliable at the moment of an incident.
How many devices does a machine need?
Enough that one is reachable from every position a person may need it, assessed from the positions actually used including setting and clearing, with pull cords where a run must be covered continuously.
What is the most common practical failure?
A device that cannot be reached, usually because material has been stored in front of it, rather than a device that has failed electrically.