Part 2 SES 2000 AUTOCLAVE
Page 8 of 43 ST-SM8l
PART 2 DESCRIPTION
from the electrical supply prior to cycle start, and
following cycle completion, to give additional
protection.
Heater Cycling Thermostat (Fig. 4 items 2 and 3).
This is connected in series with the solid state
relay to the heating element. It is operated by a
fluid-filled capsule clamped to the heating element
which will cause the thermostat cut-out device to
operate if the heater surface temperature exceeds
a preset limit, safeguarding the autoclave. The
cut-out is self-resetting and will remake when the
temperature drops. Note that operation of the
thermostat cut-out during the drying phase of the
cycle is quite normal.
Thermal Fuse (Fig. 4 item 7). This is connected so
as to remove power from the heater if a serious
overheating condition should occur. Note however
that operation of this device is unlikely to occur
since the heating element is already protected by
the heater cycling thermostat.
Fuses (Fig. 4 items 9 and 10). The unit has four
fuses as follows:
Three fuses on the rear panel of the cabinet,
rated as shown under Technical Data. The
two larger fuses are connected into the ‘mains’
supply to the unit. The smaller fuse protects
the primary circuit of the transformer.
A fourth fuse, on the printed circuit board and
rated at 2A, protects the secondary circuit of
the transformer and other parts of the
controller.
Note: Units with a printer have an extra fuse which
is fitted on the printer PCB.
Transformer (Fig. 4 item 11). This converts the
incoming mains voltage to 20V a.c. to operate the
controller and the water fill and discharge valves.
A non-resetting thermal fuse is fitted in the
transformer secondary; check for secondary
‘continuity’ when fitting a replacement transformer.
Water Fill Valve (Fig. 3 item 1). This valve is used
to control the water fill sequence. It is electrically
operated from a 24V d.c. supply which is generated
and signalled from the controller.
Discharge Valve (Fig. 3 item 2). This valve is used
principally at the end of the sterilizing cycle to
allow water and steam vapour from the chamber
to pass back into the reservoir. It is also operated
at other times during the cycle. The valve is
electrically operated from a 24V d.c. supply
generated on the controller board.
Printer Interface Board (Fig. 4 item 20). This
board is fitted in autoclaves which have a printer.
The board interfaces the printer with the integrated
microprocessor-based control board.
Air Valve (Fig. 3 item 6). At the start of a cycle the
chamber is full of air, and for a satisfactory result
almost all of this has to be removed. This is done
by a small air valve. This valve contains a ball and
spring which allows air displaced by the steam
generated in the chamber to pass out into the
reservoir. Once steam starts to pass the ball, the
ball then lifts and seals. A small ‘bleed’ remains,
however, and it is quite normal for small quantities
of steam to escape into the reservoir throughout
the cycle.
Safety Valve (Fig. 3 item 5). This is fitted on the
manifold at the rear of the chamber, and is factory
set to release excess pressure from within the
chamber. It is a primary safety device and should
not be readjusted.
Temperature Sensor (Fig. 4 item 4). This is used
to sense the chamber temperature and is fitted on
the manifold in a position where the manifold is
exposed to a small volume of steam bled through
the air valve. This device with its associated leads,
mounting plate and connector, together form a
single assembly. The sensor controls the
temperature within the chamber and also the
display temperature.
Thermocouple Entry Port (Fig. 4 item 19). This
can be used to insert a thermocouple into the
chamber ‘drain line’ to allow the operating
temperature to be measured and adjusted if
necessary.
Water Drain Pipe (Fig. 3 items 8 and 9). This
provides a means of emptying the reservoir for
cleaning or for transportation.
PCB Controller Board (Fig. 4 item 12). The
autoclave has an integrated microprocessor-
based controller. The controller handles every
aspect of management of the machine which
includes operation and control of the digital display,
the light emitting diodes and response to the
programme selection push buttons. The controller
receives information from the temperature sensor
and from the door interlock switch and is able to
detect a number of errors, and the times relative
to the cycle run when these occur. In addition to
controlling the sterilizer in the user mode, the
controller also supports a ‘demonstration’ and an
‘engineering’ mode (see Special Operating
Modes). The controller operates the heater via the
solid state relay and also controls the operation of
the water fill and discharge valves. A detailed
knowledge of the operation of the controller is not
necessary in order to service the autoclave; it is a
replaceable sub-assembly and should only be
changed as a last resort.
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