Parr Instrument Series 4558 - Manual (Page 18)

4555 - 58 Series
5G & 10L Pressure Reactors
- 17 -
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 admitting 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 provided for expansion when the liquid is heated. This
hazard is explained in greater detail in a warning statement included in the Safety
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Liquid samples may be withdrawn from the sampling valve attached to the same adapter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.
The Shaft Seal
The stirrer shafts on these reactors are sealed with a magnetically coupled gland.
Operating and Maintenance instructions for these are provided in Instruction Manual No.
234M.