Service manual

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 24V (via P54:3) from
the main block 4 MONITORING.