Parr Instrument 4700 - Manual (Page 8)

General Purpose Pressure Vessels
P a r r I n s t r u m e n t C o m p a n y 8
Vessels with an O-ring seal
The self-sealing design features an O-ring retained
in a groove on the vessel head. This design is self
sealing and the split ring does not require or have
the compression bolts used with the flat gasket.
Vessels with a Flexible Graphite Gasket
The closure bolts may be tightened using either an
open-end wrench for smaller vessels where the bolt
torque requirement is less or with a torque wrench
where additional loading is required for the higher
operating pressures.
Some of the gasket numbers shown in the attached
table are furnished with vessels that have different
maximum working pressures. We have shown the
maximum torque value to correlate to the maximum
working pressure of the vessel.
It is important to make sure that the bolts are
periodically lubricated with a high-temp anti-seize
compound to insure that they move freely so that
the desired torque value is obtained in the tighten-
ing procedure.
It is also important to insure that there is uniform
loading on all of the bolts. Make sure that the head
sits levelly on the cylinder. Install the split ring and
tighten all bolts finger tight.
Pick a starting position and tighten the bolt to 5 or 10
ft-lbs depending on the maximum amount of torque
to be applied. For those vessels with a maximum
torque requirement of 15 ft-lbs, a 5 ft-lb increment
is appropriate. For vessels with a maximum of 135
ft-lbs, 20 ft-lb increments may be used.
Bolt tightening should continue in a criss-cross
pattern from the initial bolt with the second bolt 180
degrees from the first and continuing until all bolts
are tightened. Repeat this procedure increasing the
torque to the required level as shown in the table
below.
Torque Required For Sealing Vessels
with Flexible Graphite Gaskets
Vessel
Series
No.
Maximum
Working
Pressure, PSI
Graphite
Gasket
No.
Torque
Required
ft-lb
4600 1900 315HC4KL 35
4790 3000 to 5000 429HC2KL 15
4760 3000 457HC3KL 35
4650 5000 to 6000 457HC3KL 40
4660 1900 655HC3KL 35
4680 5000 1808HCKL 40
4670 3000 1812HCKL 35
4740 8500 1829HCKL 15
4676 1900 1559HC2KL 135
Note: It may be possible to extend the life of
the Flexible Graphite gasket by coating both
sealing surfaces of the head and cylinder as
well as the gasket itself with a silicone base
lubricant. Additionally, it helps to rough up
the cylinder lip with 120 grit sandpaper to
insure that the gasket remains in the head
recess and does not stick to the cylinder.
Vessels with a Metal Gasket
Pressure vessels with a metal gasket require a
uniform loading on the gasket carefully applied by
tightening a ring of compression bolts with a torque
wrench. The amount of torque to be applied will
vary with different vessels and with the intended
maximum working pressure. Specific sealing
instructions will be provided for any Parr pressure
vessels with a metal gasket furnished on special
order.