Parr Instrument Series 4560 - Manual (Page 12)

Mini Bench Top Reactors
P a r r I n s t r u m e n t C o m p a n y 12
Pressurizing the Vessel
Check all valves carefully before admitting gas into
the system. The liquid sampling valve must remain
closed throughout the charging procedure. The gas
release valve must also be closed unless the vessel
is to be purged, or unless there is to be a continuous
fl ow through the reactor during a run. Always make
certain that the pressure in the gas tank is greater
than the pressure in the vessel; otherwise liquid
will be forced out of the vessel and into the gas
tank when the inlet valve is opened. If there is any
possibility that the tank pressure might not be high
enough to force gas into the reactor, install a one
way check valve (optional) in the gas line to prevent
any reverse fl ow.
With the inlet valve open and the fl ow control valve
on the gas tank closed, open the main valve on the
gas tank only about one-quarter turn; then use the
fl ow control valve or the valve on a pressure regula-
tor to control the fl ow of gas into the vessel. After
the desired pressure has been reached, close the
tank valves and the vessel inlet valve and discon-
nect the hose at the vessel end.
Do Not Overfi ll the Vessel
Always watch the pressure gage closely when ad-
mitting gas so as not to exceed the maximum work-
ing limit. Remember that any subsequent increase
in temperature will raise the pressure. Also, be
sure that the amount of liquid placed in the vessel
is carefully controlled. As a general rule, the liquid
charge should not exceed two-thirds of the capac-
ity of the cylinder. Too much liquid in the vessel can
lead to development of dangerous pressures if suf-
fi cient space is not provided for expansion when the
liquid is heated. This hazard is explained in greater
detail in a warning statement included in the Instruc-
tion Manual No. 230M.
Releasing Pressure
Use the gas release valve to reduce the pressure in
the vessel if the reactor is accidentally overcharged
when fi lling. Use this valve also to release any
excess pressure during a run and to exhaust the
vessel at the end of a run. If the discharge gases are
fl ammable or toxic, discharge to an exhaust hood or
to any other safe release point.
Withdrawing Liquid Samples
Liquid samples may be withdrawn from the sam-
pling valve attached to the same adapter as the gas
inlet valve whenever the vessel is pressurized. Al-
ways close the inlet valve before withdrawing a liq-
uid sample and open the sampling valve cautiously
because liquid will be discharged with considerable
force. Be particularly careful if the temperature of
the sample is above its boiling point at atmospheric
pressure. If so, it will “fl ash” and be lost as soon
as it is released from the vessel. This problem can
be avoided by connecting an optional 4351 Sample
Collection Vessel to the sampling valve to collect the
liquid into an appropriate receiver. The addition of
a small amount of gas can be used to clear the dip
tube between liquid samples so that the next sam-
ple drawn through the tube will truly be representa-
tive of the mixture.
Initial Operating Test
Read all operating instructions carefully so as to be
well acquainted with the correct procedures for han-
dling the vessel and for operating the controller and
other accessories. An initial operating test should
be made, with only water, to check the apparatus
before starting the fi rst experimental runs. For this
initial test, fi ll the cylinder not more than half full of
water and run the temperature up to 150 ºC while
checking the apparatus for leaks and observing the
performance of the temperature controller.
Internal Cooling Loop
Each Mini Reactor (except the 100 and 160 mL sizes)
has a single loop cooling coil installed in the ves-
sel with compression fi ttings on the head for con-
necting 1/4” copper or plastic tubing to the loop.
(Special 1/8” OD spiral coils can be furnished for
100 mL & 160 mL if required. Due to internal space
limitations these coils are attached with male con-
nectors on the top side of the head thereby making
the coil captive.) A slow, continuous fl ow of cold
water through a cooling loop proves a very effec-
tive means for controlling temperature overshoot
in these reactors, particularly when operating at
temperatures below 150 °C. Water fl ow through the
loop can be controlled automatically using a sole-
noid valve in the cold water line, and connected to
the cooling socket on the rear panel of the Tempera-
ture Controller. With this arrangement, cold water
will be admitted to the cooling loop whenever the
controller calls for cooling.
If internal cooling is not desired, the cooling loop
can be removed and the opening in the head can
be closed with No. 79HW, 1/8” NPT plugs. Option-
ally, other 1/8” NPT threaded fi ttings can also be
installed in the coil openings.