JULY 19, 2017
7
STM-E, STM-EL, STM-EX & STM-ELX STERILIZERS
PRESSURE ACTUATED TEMPERATURE CONTROL
STM-EX AND STM-ELX
The pressure actuated temperature control, located be-
hind the control panel assembly, governs the manufac-
ture of steam by controlling the input of electric current to
the heating elements.
HOW IT WORKS
When the timer is set, rear and front contactors will be-
come energized allowing input of current to the tempera-
ture control, thus closing the contacts completing the
current to the heating elements. Steam will then be gen-
erated within the sterilizing chamber.
The steam pressure within the sterilizing chamber is
transmitted by means of a tube to the bellows of the tem-
perature control; as the steam pressure increases, its
compression action on the bellows causes the contacts
to make or break according to the condition of the pres-
sure at that time (
rising or falling
).
Switch #1 on the control is set to cut out on rising pres-
sure at 0.95 kg/cm2 and to cut in on falling pressure at
0.91 kg/cm2 (controlling the two outer banks of heating
elements). Switch #2 is set to cut out on rising pressure
at 1.09 kg/cm2 and cut in on falling pressure at approxi-
mately 1.05 kg/cm2 (controlling center heater element
only).
Thus, a balancing effect of steam pressure build-up and
heater element current is constantly maintained during
the sterilizing cycle. When the Timer signifies the end of
the cycle, the electric current to the contactors will auto-
matically be broken.
Figure 6
CHECKING THE 110°C. SETTING, STM-ELX
The Unit should be completely evacuated then tempera-
ture selector dial turned to 110
o
C Centigrade. Observe
the current until it takes a sharp drop to approximately
one-third of the full load; at this instant, there should be a
corresponding chamber pressure of
0.14 kg/cm
2
.
Observing the current further will show another sharp
drop to approximately 1 Amp; at this instant, there should
be corresponding chamber pressure of
0.43 kg/cm
2
and
a temperature reading of 110°C Centigrade, on the tem-
perature gauge.
ADJUSTING THE RANGE OF OPERATION, STM-ELX
The range of operation of Model STM-ELX is adjusted by
simply turning the adjusting knob on the outside of the
Control Panel. A counter-clockwise turn decreases the
pressure while a clockwise turn increases the pressure.
Observe pressure and temperature gauges and adjust
knob as required.
NOTE: When resetting this control for elevations above
sea level, a correction of 0.13 kg/cm2 per kilo-
meter elevation is necessary.