6
EXPLANATION OF SYSTEM OPERATION
With the water level established, door tightened,
Power Switch 'ON', Dryer switch to Dryer 'OFF',
(Autoclave 'ON'), and Timer selection made, the
autoclave will begin heating. Illuminated indicator
lights will verigy that heating and timing circuits
are operational.
During the first stage of vessel heating (approx.
10 minutes from ambient) cold air will be purged
from the vessel so that uniform heat is attained
before pressurization of the vessel. A normally
open solenoid valve allows this purging action until
the steam temperaute in the purge line reaches
3°C above the boiling point of water.
The Sensor (temperture-sensitive switch) located
in the purge line is factory set at 103°C. The sensor
switch is normally oopen until heated to 103°C, at
which time this switch closes, energizing a latching
relay. Thje latched relay energizes the solenoid
valve, closing the purge line. The relay will remain
latched until the Timer runs out or until power is
removed. If there is a power interuption, the relay
will unlatch, the solenoid valve will open; steam
will enter the purge line, the Sensor switch will
sense the steam temperature and close, the realay
will latch and the solenoid valve will close. This
take s approximately 6 seconds.
The autoclave Temperature Control is a pressure-
sensitive switch witha sensitivity of less than 2 PSI.
When the desired autoclave temperature is
reachedm, the normally closed Temperature
Control Switch will open; according to the
relationship that exists between temperature and
steam pressure. The element will stop heating
and the temperature indication light will extinguish.
The temperauter and pressure will drop, the switch
will close and the element will begin to heat again.
This cyclic action will continue until the Timer runs
out. Them temperauter indicatiing light will verify
the operation of the Temperature Control Switch.
The autoclave is provided with two safety devices,
a low water cut-off switch and a pressure relief
valve.
The low water cut-off switch will be activated if the
unit is allowed to run out of wate, caused by not
filling vessel to water indicator at the beginning of
each cycle or due to purge system failure in which
water is boiled out of the system. The normally
closed contacts, on this snap-action thermostat
switch, will open when it senses and outside vessel
temperature of 132°C and will close again at
110°C. It opens the circuit to the heating element.
The timer will continue to operate and will shut the
unit off when the set time has elapsed.
The Pressure Relief Valve is located in the
condenser tank assembly. It is a safeguard against
temperature control failure in which case the
autoclave heating element would overheat the
vessel giving a corresponding increase in
pressure. The pressure relief valve will open when
the vessel pressure reaches 35 PSI ± 3 PSI,
venting steam into the condensor tank. If not is
around to notice the malfunction, the relief valve
will vent pressure form the vessel until the water
is boiled out. The low water cut-off switch will then
shut off the heating circuit as previously described.
The condensor tank collects purged water and
condensed steam. It should be drained after every
cycle with the drain valve and drain hose fitting
located onthe control panel.
The 8100-TD is equipped with a drying element.
NOTE: The dryer should be used with the door
ajar. It is operated by turning the Power Switch
'ON', Dryer Switch to 'Dryer ON' position setting
the timer and selecting the desired drying
temperature in the dryer Temperatuer Control. The
Dryer Temperature Control is an infinite control
which varies the cyclic on-off rate of current being
supplied to the dryer heating elemetn and thus
controlling the temperature inside the vessel. This
control is variable from Low position to High
position. Low corresponds to approx. 50°C,
medium is approx. 90°C and high corresponds to
approx. 150°C. These measurements were taken
with a thermocouple mounted in a 14 pin plastic
dip integrated circuit, positioned in the center of
the S.S.T. Tray supplied with the unit. The door
was opened 1/4" from vessel during test.
