page 37 of 91 USB-QFLCII-14804/0
4.4.1 Locking mechanism requirements
Unlocking the flap blade To allow for the opening of the flap blade, the locking mechanism's
electromagnet must be operated with a control current. The locking unit’s
locking pin is retracted and the locking lever is released. The air flow,
created by the fan, will open the flap blade. The electromagnet is now
effected via 2 x 24 V DC relay signals of an external control.
DANGER
The locking mechanism’s electromagnetic release should only operate
for a very short period during the start-up process and must not be
“live” during operation.
If the electromagnet is constantly live, this can result in the flap blade not being
locked in the event of an explosion. Should this occur, the inlet isolation device
would not properly isolate the explosion or stop flames from traveling to
upstream system areas!
a) We recommend operating the electromagnet simultaneously with the
fan's starting signal for a duration of 2 seconds (adjustable).
b) At star/delta switch-on or in frequency inverter operation of the fan, it is
necessary to adjust the electromotor's control time to the system's
start-up behavior during the first commissioning.
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Monitoring the locking
mechanism Except for the described system start, no other electrical control of the locking
mechanism’s electromagnet may occur. To ensure that no other control
happens, the system must be designed in such a way that both 24 V DC
signals for the control of the electromagnet are additionally fed to the control
system as an input signal, After expiration of the control time, both terminals
at the locking mechanism have to be currentless ("logic zero"). This will
ensure that the currentless locking mechanism allows for a lockdown of the
flap blade in the event of an explosion and prevent the flap from opening.
If a signal is live at one of the two terminals at the monitoring panel (one
terminal does not shut down), the locking mechanism would not properly
lock down the flap blade in the event of an explosion.
The result would be that the flap blade would not be locked in the closed
position, and the inlet isolation device would not function as intended (would not
hold back flames/pressure). Explosion pressure/flame passage to upstream
system areas could be the result.
If both wire terminals at the monitoring panel do not switch to "logic zero" (if one
of the two wire terminals does not shut down), a malfunction must be indicated
at the monitoring panel and an emergency shutdown must take place.
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