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Astell Autoclaves/Sterilisers – AMB220 | AMB230 | AMB240 | AMB420 | AMB430 | AMB440 | AMA240 | AMA440
CLOSURE SYSTEM INTERLOCKS
The cover is prevented from being opened by a solenoid
locking bolt pin. This locking bolt pin engagement and
cover position is sensed by high-reliability micro-switches.
The system cannot be started unless the closure is fully
secured and locked. The closure interlock system senses
the position of 2 of the sliding bolts that hold the cover
shut, and also detects the “engaged” position of the
solenoid locking pin that prevents the handle being
moved.
The cover cannot be opened if:
• The chamber temperature is above programmed
cooling lock setting and pressure is above approx.
0.1 bars
• The program cooling lock temperature is set within
each program, but the pre-set cool lock temperature is
a single setting applying to all programs
• The cover is also locked if power is off
• There is a delay of typically 5 seconds after pressing
the door button before the locking pin retracts, and
during this the vent valve is open to atmosphere
• The cover can only be opened by pressing the door
button and waiting for the bolt to unlock
HEATING SYSTEM
Steam is generated from water held in the base of the
chamber. The electric heating system uses an electrical
immersion heater and a water level conductivity sensor
acts at filling level.
An over temperature thermostat limits heater temperature
rise if the system should fail or boil dry.
FREE STEAMING SYSTEM
Note:
“free steaming” is the term used here to describe
an initial period of steam flushing at atmospheric pressure
which uses the steam to displace the air from the
chamber.
The program profile control provides an adjustable period
of free steam to ensure steam penetration in loads such
as petri dishes, sample tubes, etc. with large numbers of
trapped air spaces.
The temperature at which this starts is just below water
boiling point. This can be adjusted to allow for altitude
effects.
TEMPERATURE CONTROL SYSTEM
The chamber temperature is measured by a PT100
precision sensor. This measurement is compared with the
sterilize temperature. The set point stored in the program
profile, and the controller acts to keep the chamber at or
about that temperature by switching the heat source on
and off. Control of temperature does not rely on steam
pressure.
The actual temperature that the control system attempts
to attain is varied automatically at different parts of the
cycle. This does not require user attention during the
cycles.
STERILIZE TIMING SYSTEMS
• Standard timing system
This operates if load sensed timing option is not fitted,
or if fitted but it is not selected for this program. Timing
starts when chamber reaches set temperature, and
terminates sterilization at end of set period. Temperature
and time are set within the program.
• Load sensed timing system (optional extra)
Load sensed timing is selectable (on or off) within each of
the programs.
COOLING
Cooling action operates when appropriate in the program
and only works for program types that do not permit
drying, e.g. fluids cycles
At the end of sterilize initially convection ambient cooling
cools the chamber to a pre-set pressure threshold without
the assisted cooling fan system running and the chamber
then continues to cool until the cooling lock(s) are
satisfied.
If the cooling fan option is fitted the fans will start at an
appropriate temperature, normally pre-set to 105°C,
which may be adjusted if required.
DRYING
The autoclaves can be equipped with an optional Air
Drying system. This includes an air pump that during the
drying stage draws air through a filter and blowing air
above the heater when it pulses to remove moisture and
facilitate the drying operation. Drying is performed with
the door closed.