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 a Flat PTFE or 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. Unless otherwise note on
documentation accompanying the product, recom-
mended torque values are shown alongside respec-
tive model numbers in subsequent pages on this
operating instruction manual.
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 level 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.
For vessels with PTFE Flat Gasket, after recom-
mended torque value is reached, let the vessel
stand for about five minutes then re-tighten again to
recommended torque value. This will compensate
for any tendency of the PTFE gasket to flow under
the loading.
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.
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
properly 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, increas-
ing the torque until all have been tightened to the
recommended 15 ft-lb limit.