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Astell Autoclaves/Sterilisers – AMB220 | AMB230 | AMB240 | AMB420 | AMB430 | AMB440 | AMA240 | AMA440
SAFETY INTERLOCKS
Pressure interlock
Pre-set to less than +0.1 Bar this is an independent
electrical interlock operated by a precision pressure switch
preventing the electrical release of the door bolt if the
chamber is pressurised.
Overpressure cut-out
This is pre-set to approx. 3.00 Bar. Above the safety valve
point, and operated by the electronics control software. If
the pressure sensed by the controller pressure transducer
exceeds this level, which suggests safety valve problems,
then the heating is shut down, a warning shown and a
fault condition generated.
TEMPERATURE INTERLOCKS
Starting- interlock
Prevents starting a cycle with a dangerously hot or
pressurised chamber.
Cooling locks
There are two cooling locks to prevent the steriliser being
opened with a liquid load under unsafe conditions.
There are two cooling lock systems. They remain
electrically locked until the load has cooled to a safe
handling temperature cooling locks operate for destruct
programs.
Warning- the cooling locks can present a hazard if
incorrectly set.
They should be adjusted by the supervisor, or a person
trained in steriliser use and the setting of safe steriliser
cycles.
Pre-set cooling lock thermostat
This is a thermostat with dial and scale calibrated in
0-100°C at the rear.
It measures temperature of the chamber outer wall,
with sufficient thermal mass for a reasonable match
between the load temperature and the cooling lock set
temperature.
Note:
The temperatures will not be quite the same, due
to differing thermal inertia, between the chamber wall
and the load. Normally the chamber wall and cooling lock
sensor attached to it will cool down faster than the load.
PROGRAM COOLING LOCK
The standard system operates when load sensing option
is not fitted or not selected.
This uses a cooling-lock-temperature set by the user
within each program profile which is compared with the
chamber internal temperature sensor reading (the same
temperature as appears on the temperature display).
When the chamber temperature is above this “program”
cool-lock temperature the lock is active (engaged)
and completion is inhibited preventing the door from
unlocking.
Note:
The chamber-sensor detects the temperature
within the steam space and it will normally cool faster than
the load and/or the chamber wall.
Load sensed cooling lock
If load sensed cooling option is fitted and selected for
that program
In this case the cooling lock temperature set for the
program is not compared with the chamber temperature
but instead the temperature measured by the flexible
load sensor. When this load-sensed temperature is falling
but still above the program’s cool-lock temperature the
lock is active (engaged) and completion is inhibited, so
the door cannot be unlocked.
As the load sensing probe detects the temperature within
the load itself, it will always represent the actual load
temperature, assuming it has been correctly placed in the
load.
Dual cool locks
Both cooling locks must be satisfied for them to release
the door.
The temperature of load and chamber must both be
below the two separately-set cool-lock temperatures to
allow the cycle to complete.
Typical view of cooling lock thermostat