JVL MAC050 User Manual page 389

6.7 Emergency stop considerations
An emergency stop is not required only in cases where it is completely evident that an
emergency stop would not prevent an injury, minimise an injury or stop an injury.
In practice this means that essentially all machines must incorporate an emergency stop
function.
It must be emphasised that a machine's emergency stop function is NOT a preventive
measure, but is regarded as a supplementary measure. This means that the protective
measures that must be implemented as a result of the machine's risk assessment cannot
be replaced by an emergency stop function.
The protective measures required must be implemented such that they are reliable, i.e.
not themselves prone to error or failure. The extent to which this is required depends
on the risk that the actual protective measure is designed to eliminate, i.e. the greater
the hazard, the more secure and reliable the protective measure.
Protective measures and the emergency stop function are often implemented using the
machine's electrical control system.
For guidelines on how the control system's safety related components can be
implemented, related standards can be used.
6.7.2 EN 60204-1
DS/EN 60204-1 is applicable for the general requirements of a machine's electrical sys-
tems.
This standard defines several stop categories, paragraph 9.2.2 Stop functions in DS/EN
60204-1
There are three categories of stop function as follow:
- Stop category 0: stopping by immediate removal of power to the machine actuators
(i.e. an uncontrolled stop – paragraph 3.56 in DS/EN 60204-1).
- Stop category 1: a controlled stop (paragraph 3.11 in DS/EN60204-1) with power
available to the machine actuators to achieve the stop and then removal of power
when the stop is achieved.
- Stop category 2: a controlled stop with power left available to the machine actuators.
Requirements are given that a stop function must be incorporated (paragraph
9.2.5.3 Stop in DS/EN 60204-1)
Stop category 0 and/or category 1 and/or category 2 stop functions shall be provided as
indicated by the risk assessment and the functional requirements of the machine
(paragraph 4.1in DS/EN 60204-1).
NOTE: The supply disconnecting device (paragraph 5.3 in DS/EN 60204-1) when
operated achieves a stop category 0. Stop functions shall override related start functions
(see §9.2.5.2 in DS/EN 60204-1).
Similarly, requirements are specified for the implementation of an emergency stop func-
tion:
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