Siemens Servo Ventilator 300, Service Manual

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2
Servo Ventilator 300/300A Description of functions
E382 E380E 061 01 03 01 Siemens-Elema AB 69
11.4 Safety valve
The safety valve function depends on its
solenoid and on its factory trimmed springs.
The solenoid can be electrically activated
only from the 11.5
SAFETY VALVE DRIVER
. When
the valve is opened it connects the
INSPIRATORY PIPE
directly to ambient air thus
enabling a decrease in pressure. The valve
can open in two different ways.
1. When the solenoid is not activated (via
the
SAFETY VALVE DRIVER
) the mechanical
spring which is built into the solenoid
pushes the solenoid axis upwards. This
actuates the safety valve to be opened.
This is normal safety (pop off) function.
This is also the case when the
MODE
SELECTOR
is set at Ventilator Off.
2. The two springs which hold the safety
valve disc in position are factory
trimmed to a tension such that the
SAFETY VALVE
will let out gas if the
pressure inside the
INSPIRATORY PIPE
should exceed 120 cm H
2
O (even if the
solenoid is activated). This is an extra
safety function, and the situation will
normally not occur.
During start up, the solenoid is electrically
activated so that the solenoid axis is pulled
down (with a clicking sound). This is the
normal operational position of the solenoid;
the
SAFETY VALVE
is normally kept closed.
11.5 Safety valve driver
The
SAFETY VALVE DRIVER
consists of the
electronic board PC 1613 with three
connection cables:
• It is connected (at the connector P53) via a
cable to the 21
POWER SUPPLY
. The safety
valve is protected by a PTC resistor in the
21
POWER SUPPLY
.
• It is connected (at N54) via a cable to the
board PC 1607
PNEUMATIC INTERCONNECTION
(connector P23).
• It is connected (at N55) via a cable to the
11.4
SAFETY VALVE
solenoid. The function of
this block is to provide power to the
SAFETY
VALVE
solenoid controlled, by the input
signal
DIS SAF VALVE AND
24
V
(via P54:3) from
the main block 4
MONITORING
.