Parr Instrument Series 4590 - Manual (Page 15)

4590 Micro Reactors
w w w . p a r r i n s t . c o m 15
Gas Connections
For a gas connection to the vessel, use the A495HC
pressure hose (A506HC in high pressure reactors)
furnished with the reactor. Attach the hose to a pres-
sure regulator or flow control valve on a commercial
gas cylinder using PTFE tape or other thread sealant
on the 1/8” NPT male nipple and on the 1/4” NPT
bushing, if used. Then screw the Type A coned pres-
sure fitting into the adapter attached to the gas inlet
valve and tighten the compression nut firmly. Do not
use any thread dope or tape on the coned fitting. The
A495HC pressure hose is made of reinforced Nylon
which can be used for all non-corrosive gases at
pressures up to 2500 psig. For operations involving
corrosive gases, this hose should be replaced with
an A490HC hose (optional) which has a PTFE lining
and a braided stainless steel outer covering. These
hoses have the same fittings as in the A495HC.
Alternately the A506HC for high pressure systems is
made of T316 Stainless Steel tubing.
Note: For high pressure applications involving cor-
rosive gases please contact Parr Customer Service.
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
flow 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 flow.
With the inlet valve open and the flow control valve
on the gas tank closed, open the main valve on the
gas tank only about one-quarter turn; then use the
flow control valve or the valve on a pressure regula-
tor to control the flow 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 Overfill the Vessel
Always watch the pressure gage closely when admit-
ting gas so as not to exceed the maximum working
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 capacity of the cylinder.
Too much liquid in the vessel can lead to development
of dangerous pressures if sufficient space is not provid-
ed for expansion when the liquid is heated. This hazard
is explained in greater detail in a warning statement
included in the Instruction Manual No. 230M.
Releasing Pressure
Use the gas release valve to reduce the pressure in
the vessel if the reactor is accidentally overcharged
when filling. 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 flammable or
toxic, discharge to an exhaust hood or to any other safe
release point.
Withdrawing Liquid Samples
Liquid samples may be withdrawn from the sampling
valve attached to the same adapter as the gas inlet
valve whenever the vessel is pressurized. Always close
the inlet valve before withdrawing a liquid 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
“flash” 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 sample drawn through the tube will truly be
representative of the mixture.
Initial Operating Test
Read all operating instructions carefully so as to be well
acquainted with the correct procedures for handling
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 first experimental runs. For this initial test, fill 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 tem-
perature controller.
Note: The following steps are common to both head configurations.