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Astell Autoclaves/Sterilisers – AMB220 | AMB230 | AMB240 | AMB420 | AMB430 | AMB440 | AMA240 | AMA440
COMMISSIONING AND
PROGRAM SETTING
This section describes how to derive the settings that
you may need to enter for your intended program(s).
The description applies to discards loads but a similar
approach can be applied to instrument/glassware.
A “program” consists of three process sections plus cool
lock settings. Any of these are independently selected
and adjustable.
• Free steaming at 95°C forces the air out from the
chamber
• Sterilising at set point temperature for selected time
• Cooling locks set temperature
The program values can be determined by trial-and-error,
but as this can be very long and involved, it is best to use
a chart recorder to investigate the temperature - time
behaviour of the load. A number of settings must be
made.
Free steaming
The free steaming time depends on the nature of the
load. Items such as trays or racks, solid items, bowls, etc.
have low thermal mass and do not trap much air, and
will sterilize quite satisfactorily with minimal, typically 5-7
minutes of free steaming time. However, larger loads with
larger boxes of bottles, phials, petri dishes, etc. Have a
larger thermal mass and trap a great deal of air. These
are always needed a longer free steaming time. The free
steaming time should be set to give at least 3 minutes of
active free steaming.
Insufficient free steaming causes excess pressure in the
chamber for the temperature, and a higher peak-peak
fluctuation in temperature which will trigger the chamber
(or load) temperature fault alarm.
Determining suitable sterilize and air-purge
times
The chamber will heat-up to sterilise temperature
before the load catches up, and this time delay must be
accounted for to ensure correct sterilisation.
The load sensed timing option (if fitted) compensates for
the time-lag automatically and only requires the sterilising
time to be entered.
If the time-lag for the load to catch up with the chamber
is known from another machine, or can be adequately
estimated then this may be added to the desired
sterilising time and the total set as the sterilize time for
the program.
In most cases the behaviour of the load in this
arrangement is unknown, so it is necessary to use a chart
recorder or multi-thermocouple indicator to monitor the
load, and find the ideal free steaming and sterilise times.
Use of a temperature recorder or data-
logger for commissioning measurements
Arrange a multi-pen thermocouple chart recorder or
indicator to monitor the temperature in the load and in
the chamber. For a complex load, the steam penetration
is the slowest into the more enclosed parts, such as the
centre of stainless steel buckets. In this case, the very
centre of each container should be monitored with the
sensor inside a load item (e.g. a petri dish). Other points
throughout the load may be monitored depending
on how many thermocouple sensors are available. If
desired sterilising monitor tapes or spore strips may be
distributed throughout the load.
Load sensing option
The process to determine the time settings differs if
load sensed timing option is fitted and selected. If it is
available on your machine, you must decide whether it is
necessary or desirable to use it or to select the simpler
timing system. You should choose to use this if the heat
up time of the load may vary from cycle to cycle, e.g. if the
size of loads varies widely.