Parr Instrument Series 4520 - Manual (Page 14)

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4520 Bench Top Reactors Parr Instrument Company
HOW TO USE THE VESSEL
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Continued )
For applications involving corrosive
gases the nylon hose should be replaced
with the A490HC hose which includes a
PTFE lining and a braided stainless steel
outer covering. The A506HC hose is
constructed of T316 stainless steel (or other
corrosion resistant materials) is also
available for severe conditions.
Pressurizing the Vessel
Check all of the needle valves before
introducing gas to the vessel. The A122VB
liquid sampling valve must be in the closed
position throughout the charging procedure.
The gas release valve should also be in the
closed position unless it is to be used to
purge the vessel or run in a continuous
mode of operation.
It is important to make certain that the
pressure in the gas tank is greater than the
pressure in the vessel. If the vessel
pressure is greater than the gas tank , liquid
will be forced out of the vessel and into the
gas supply when the inlet valve is open. If
there is any possibility that the gas tank
pressure might not be sufficient, install a one
way check valve in the gas line to prevent
any reverse flow. (Hoses with check valves
are available upon request) After the
desired pressure has been reached, close
the valves and disconnect the hose
assembly at the vessel side.
Do Not Overfill the Vessel
Monitor the pressure gage of the vessel
when admitting gas. Be aware of the
maximum pressure limits of the vessel and
allow for expansion as a result of the heating
process.
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 the development of
dangerous pressures if sufficient space is
not available for expansion when the
material is heated. See the Safety
Instruction Manual No. 230M for additional
details and potential hazards.
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Liquid samples may be withdrawn from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.
Releasing Pressure
The gas release valve is used to reduce
the pressure in the vessel if the system is
accidentally overcharged when filling. It is
also used to release any excess pressure
during a run and to exhaust the vessel at the
end of a test.
If the discharge gases are flammable or
toxic, a line should be added to the valve to
discharge into an appropriate containment or
exhaust system.