Parr Instrument 4575/76 HP/HT - Manual (Page 13)

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4575/76 HP/HT Pressure Reactors
13
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 regulator 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 disconnect the hose at the vessel end.
Do Not Overfill 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-
ficient 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 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Liquid samples may be withdrawn from the sam-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 “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 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 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 reactor controller.