Parr Instrument 4700 - Manual (Page 9)

General Purpose Pressure Vessels
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Sealing 4740 High Pressure Vessels
Closing operations for the 1.0 inch I.D., Series 4740
high pressure vessels are similar to those described
for larger vessels with flexible graphite gaskets,
except on the 4740 Series the compression screws
are carried in a screw cap instead of in a split ring.
When closing a 4740, clamp the cylinder in a vise;
check the graphite gasket to be sure that it fits prop-
erly in the head groove; set the head on the cylinder
and add the compression ring. Check the screw cap
to be sure that the six screws have been turned back
so that they do not project through the cap, and then
screw the cap onto the cylinder. Turn it down as far
as it will go, then back it off about 1/8 turn. Now,
tighten the screws with a torque wrench with an
initial 10 ft-lbs using the criss-cross pattern described
for larger vessels. After all have been tightened to
10 ft-lbs, repeat the procedure, increasing the torque
until all have been tightened to the recommended 15
ft-lb limit.
OTHER VESSEL HEAD FITTINGS
Gage Block Assemblies
Parr gage block assemblies combine the function of
an inlet valve, a pressure gage and a safety rupture
disc in a compact assembly on a block which can
be attached to the head of a pressure vessel with a
single connecting tube. There is a threaded socket
in the block for a gas connection with a pressure
hose or tubing using a Type A coned pressure fitting.
Coned pressure fittings are also used on the tube
which connects the block to the pressure vessel.
The valve in this assembly controls the flow of gas
into the vessel and the gage shows the internal
pressure when the valve is closed. Two styles are
offered: The 4316 gage block assembly has a 3-1/2”
dia. pressure gage and a Type A socket connector.
This unit is normally used on smaller vessels where
space is limited.
The 4317 gage block assembly has a 4-1/2” dia. gage
and a Type B connector. It is typically furnished on
vessels one liter and larger.
Pressure Gages
Pressure gages display in both psi and bar in vari-
ous ranges for use on Parr gage block assemblies.
The available ranges are shown in the gage block
parts list. All of these gages have stainless steel
cases with T316SS Bourdon tubes and ¼” NPT male
connections. Gages constructed of Alloy 400 are
available on special order.
Safety Rupture Discs
Detailed instructions for the safety rupture disc
installed in Parr gage blocks and heads are provided
in a separate Instruction Sheet No. 231M. The user
should review these instructions carefully. Please
note that the operating pressures in the vessel
should not exceed 90% of the range of the pressure
gage and rupture disc. Also note the warning that
the discharge port from the rupture disc must always
be directed away from all operating personnel. A
compression fitting for use with 3/8” O.D. tubing is
attached to the rupture disc body. It is recommend-
ed that tubing be attached to this connector to carry
any discharge to a fume hood or safe area in the
event of an over-pressure. The free or discharge end
of any attached tubing must be anchored securely.
Coned Pressure Fittings
The coned pressure fittings used to connect gage
blocks, pressure hoses and other detachable parts
to Parr pressure vessels are illustrated below. These
fittings have a sleeve with a left-handed thread
which screws onto the end of a thick-walled tube
plus a compression nut to complete the assembly.
When screwed into a matching socket, these parts
form a rigid joint which will remain tight over a wide
temperature and pressure range, yet the joint can be
made and broken repeatedly without destroying the
sealing faces. No gasket is required.
6 Gage
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