Parr Instrument Series 3900 - Manual (Page 10)

Hydrogenation Apparatus
P a r r I n s t r u m e n t C o m p a n y 10
Temperature Measurement and Control
4833 Temperature Controller
Reaction temperatures can be measured and con-
trolled with a Parr 4833 Temperature Controller
which operates with an A295E, Type J (iron-constan-
tan) thermocouple installed in the reaction bottle.
The thermocouple is sealed in an 1/8” diameter
stainless steel sheath and held in an A159CA bottle
connector assembly which carries both the probe
and the gas passage through a single opening in
the bottle stopper. A295E thermocouples are made
in two lengths to fi t different bottle sizes as listed on
page 30.
To install the A159CA bottle connector, remove the
existing gas inlet tube and fi ttings and install the
new fi ttings which are provided. Clamp the bottle in
the shaker with the thermocouple positioned so that
the tip of the probe reaches a point three-fourths of
the distance from the neck of the bottle. This dis-
tance can be changed by loosening the cap nut at
the top of the connector and sliding the probe up or
down in the tee fi tting.
Loop the thermocouple wire downward and fasten it
above the tee fi tting using one of the cable ties fur-
nished with the bottle connector; then run the wire
along the polypropylene tube, fastening it fi rmly
to the tube at several points to prevent excessive
fl exing and breakage. Bring the bottle heater cord
upward and fasten it under the clip at the top of the
shaker; then run the cord parallel to the shaker piv-
ots and plug it into the heater socket on the control-
ler.
To activate the heater, plug the thermocouple and
the heating mantle into sockets on the rear panel
of the controller, and connect the controller to an
electric supply that corresponds to the voltage of
the heater. Turn the DISPLAY and HEATER switches
ON, and set the controller to the desired operating
temperature using the UP and DOWN arrow keys
on the front of the controller module. The indicator
light in the heater switch will illuminate when the
switch is ON and current is being supplied to the
heater. The set point can be changed at any time
regardless of whether the heater is on or off. Copies
of Parr Bulletin 311M, Supplemental Instructions for
the 4833 Controller, and the CAL-9500 User’s Manual
furnished with the 4833 Controller provides instruc-
tions for tuning the Controller and using the alarm
features.
The 4833 Temperature Controller has dual displays:
one for the process temperature and the other for
the set point. The operating range of the Controller
covers the span from 0 ° to 100 ° C with the high
limit extending somewhat beyond the temperature
limit for the 3911 and 3921 Hydrogenators. These hy-
drogenators should not be operated at temperatures
above 80 ° C.
The 4833 Controller is sensitive to temperature
changes of less than 0.5 ° C but temperature varia-
tions in the reaction bottle may be larger than this
due to lag in the heating system and turbulence in
the bottle. In most cases temperatures in a 500 mL
bottle will not vary by more than one degree above
or below the set point. Variations in larger bottles
may run as much as two degrees, but this is still
within permissible limits for most reactions. Bottle
temperatures will tend to overshoot at low tempera-
tures in the 30° to 40° range. There will be less over-
shoot at higher settings. Overshoot can be avoided
by setting the controller several degrees low during
the initial period, then raising the temperature in
one or two steps after cycling has been established
slightly below the working level.
Fail-safe protection against a thermocouple break
is provided in the controller. This can be tested by
disconnecting the thermocouple from the controller,
which should turn off the heater.