Parr Instrument 4838 Operating Instructions Manual page 14

4838 Reactor Controller
Pressure Display Module (PDM)
PRESSURE
When this optional module is present, the left dis-
play in red shows the pressure, and the right hand
display in green shows the Pressure Alarm setpoint.
If the reactor pressure exceeds this setpoint, the
pressure module will trip the High Limit Alarm, cut-
ting power to the heater.
This module provides a digital read out for continu-
ously monitoring the pressure within the reactor,
plus a backup safety feature which will terminate
power to the heater if a preset maximum is reached.
Pressure is displayed with a 1 psi resolution and a
1% FS accuracy. The safety cut-out feature offers
excellent protection against accidental over-pressure
by allowing the user to set a maximum pressure
which, if reached, will activate the high limit relay
and turn off the heater immediately.
The signal for the pressure display is generated by
a transducer in a stainless steel housing mounted
on the reactor. The transducer must not be heated
above 120 °C; an elevated temperature can caused
the accuracy of the transducer to suffer. A water
cooling sleeve attached to the transducer mounting
body can be used to keep the transducer below this
limit when operating the reactor at higher tempera-
tures.
For applications involving reactants corrosive to
stainless steel, the transducer body can be replaced
with an isolator of special alloys which will keep the
reactants away from the transducer. Users should
consult with the Technical Support before pur-
chasing one of these.
14
The Pressure Alarm setpoint may be adjusted by do-
ing the following:
1. Press the up or down arrow until the lower
display shows the desired setpoint. The lower
display will blink, showing the value has not
been set yet.
2. Press the set button. The lower display will stop
blinking, showing the new value has been set.
When ordering a pressure display module sepa-
rately or installed in any controller, always
specify the reactor on which the transducer will be
installed so that the proper mounting hardware can
be furnished.
Note: if the pressure transducer is not attached
to the 4838 Controller, the High Limit Reset
may trip or show a fi xed but incorrect value.
We recommend always operating with the
transducer attached.
High-Temp Cut-Off Module (HTM)
TEMPERATURE
This module provides a redundant high tempera-
ture safety cut-off which will shut down the reactor
heater if an unusual malfunction should develop in
the primary control system. It is a completely inde-
pendent safety backup system, operating in addition
to the high-limit control built into each tempera-
ture controller. It has its own thermocouple, digital
display and wiring, and can be preset to shut down
the heater at any desired temperature.