Parr Instrument Series 5500 - Manual (Page 12)

Compact 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
HOW TO USE THE VESSEL
To open the Vessel
Open the gas release valve to discharge any internal
pressure. For the bolted closure, loosen the six cap
screws in the split ring sections. Loosen the cone
pointed screw in the outer band and lower the band
to rest on the table. The ring sections can now be
removed, and the head with all attached fittings is
free to be lifted from the cylinder. Handle the head
carefully so as not to damage the stirring shaft and
other internals when they are outside of the cylin-
der.
Before Closing the Vessel
Examine the head gasket or o-ring carefully to be
sure that it is in good condition. After considerable
use, some of the PTFE gasket may extrude into a
thin, ragged edge around the inside and outside
diameters. This does not necessarily mean that the
gasket must be replaced, but the extruded portion
should be removed with a sharp knife. Examine the
mating surfaces on the cylinder and head to be sure
they are clean and free from burrs; then set the head
on the cylinder.
Sealing Vessels with PTFE Gaskets
Initially tighten the cap screws to 15 ft-lbs then
increase to 20-25 ft-lbs. Tightening should proceed
in a criss-cross pattern rather than progressively
around the circle. Let the vessel stand for about five
minutes after the initial tightening; then tighten the
cap screws again. This will compensate for any ten-
dency of the PTFE gasket to flow under the loading
pressure.
Sealing with Flexible Graphite Gaskets
Initially tighten the cap screws to 15 ft-lbs then in-
crease to 20-25 ft-lbs. Tightening should proceed in a
criss-cross pattern rather than progressively around
the circle.
Flexible graphite gaskets tend to be somewhat
flakey. To extend the useful life of these gaskets, first
rough up the sealing surface of the cylinder with
120 grit sand paper to ensure the gasket remains in
the head groove and does not stick to the cylinder.
Secondly, coat both sealing surfaces with a silicone
lubricant. This process will aid in compressing the
gasket so it does not break apart after one use.
Recommended Bolt Torque
PTFE or
Flexible Graphite 0-3000 psig
(0-200 bar) 20-25 ft-lbs
O-ring Closures
The split rings used with an o-ring seal do not in-
clude any compression bolts.
With the easy close split ring, the o-ring is attached
to the pilot on the underside of the head. When
closing the vessel, set the head on the cylinder and
press down on the head until the bottom of the head
meets with the cylinder flange. Then install the two
split ring halves and attach the outer drop band.
Gas Connections
For a gas connection to the vessel, use the A495HC
pressure hose furnished with the reactor. Attach the
hose to a pressure 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 pressure fitting into the adapter attached
to the gas inlet valve and tighten the compres-
sion 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.
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.