Zander Aachen SCB Serie Betriebsanleitung Seite 58

Safety Time Control Device SCB
With the selected configuration Pr06, which allows a monitored, manual start with automa-
tic re-trigger function as well as a time-delayed switch-off of the safe relay contacts, the
SCB-02 filters a short-time triggering of the connected pressure-switch up to 10 seconds.
If an overpressure is detected, the time delay at the SCB-02 is triggered. This means that
the safe relay contacts remain closed for a period of 10 seconds.
If the pressure falls below the limit value again within this time an automatic re-triggering
of the SCB-02 takes place. This means that the running time delay is stopped and the
relay contacts remain energized.
However, if an overpressure persists after the 10 seconds, the SCB-02 switches off its
safe relay contacts. A restart is only possible again after acknowledgement via the reset-
button.
8.2 Time delayed reset
Accidental resetting of a safety system can lead to a hazard if a person is in the danger
zone at this time.
By using an SCB-04 with configuration Pr27 ("delayed reset") in combination with a safety
relay (e.g. SR3C) this can be prevented.
For this, two reset buttons are used to release a machine located in the danger zone. In
combination with the SCB-04 and two safety relays, the safety guard door, the sequence
as well as the time window for actuating the reset buttons are monitored (see Figure 3 and
Figure 4).
Reset button 1 is mounted in the danger area and reset button 2 in the safe area. Both in
such a way that the operating personnel have a clear overview of the danger area.
By pressing the RESET1 button, the safety circuit for the safety relay K2 is enabled for the
parameterised time window of 20 seconds. This is completely closed as soon as the ope-
rator leaves the danger zone through the safety door and closes it.
Now the machine can be released within the remaining time via the RESET 2 button. By
guiding the safety circuit of K2 via its own relay contacts, K2 remains in self-retaining
mode after release via RESET 2.
If the time running on the SCB-04 has elapsed before pressing the RESET 2 button, the
safety circuit of K2 is blocked again and disconnection of the machine is prevented.
Without actuating the RESET 1 button in the danger area, the machine cannot be re-
leased even with the safety door closed.
An accidental start of the machine without the knowledge of a person in the danger area is
thus safely prevented.
H. ZANDER GmbH & Co. KG • Am Gut Wolf 15 • 52070 Aachen • Deutschland • Tel +49 241 9105010
Fax +49 241 91050138 • info@zander-aachen.de • www.zander-aachen.de
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