Bosch Rexroth VCH 08.1 Manual page 44

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Technical Data
Notes on the enabling button
One imperative requirement for equipment identified in this way is, there‐
fore, that it must be possible to trigger a safe state at any time and in any
operating mode, without further knowledge of the machine (see also EN
ISO 13850). It is not acceptable for an emergency stop button to be ena‐
bled temporarily, since this can lead to faulty operation and life threatening
loss of time in panic situations.
If hand-held terminals are considered in relation to these requirements it
is evident that a differentiation must be made as to whether an emergency
stop button on the hand-held terminal may be used or not, depending on
specific criteria and applications.
Depending on the specific use case, the risk assessment of the machine
(according to EN ISO 14121-1) can lead to different results, e.g. for the
shutdown of a system. The present document cannot make the decision.
In the specific case, the machine manufacturerer has to evaluate the case
under consideration of all applying standards.
Temporarily pluggable hand-held terminlas bear the risk of being available
with ineffective safety device after having been disconnected from the de‐
vice. In this case a gray stop button would not be detected as operating
element for shutdown in case of an emergency. A disconnected hand-held
terminal with red-yellow button could be taken for such an operating ele‐
ment; and the confusion could lead to a dangerous situation. In this case
the professional organization demands "organisatory measures" for ele‐
minating the danger, e.g. shutting away the device.
● Many machines feature a normal operation mode as well as a special
operation mode. The machine fulfils its primary mission in normal (auto‐
matic) operation. In this operation mode, safety is guaranteed by closed,
separating protective devices and/or with functioning, not separating pro‐
tective devices.
The special operation modes of a machine serve to maintain normal op‐
eration. In doing so, safety must be guaranteed in a way that is different
to normal operation, because hazardous areas of the machine can now
be entered and targeted machine movements have to be possible. The
enabling button plays an important role.
This application requires the enabling button to eliminate the hazards that
are to be controlled in a timely manner, before any personal injury occurs.
For this purpose additional safety measures may be necessary, such as
safely reduced speed of drive mechanisms.
In contrast to the emergency stop button (respectively the stop button), a
machine in special operation modes with an enabling button is in a safe
state as long as this enabling button is not activated (see the following
figure):
DOK-SUPPL*-VCH*08.1***-PR02-EN-P
Rexroth IndraControl VCH 08.1 Hand-held Terminal