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
10
TUBING
NUT
BUSHING
D
E
Coned Pressure Fittings
Type
A
B
Tube Size
1/4”
3/8”
Thread (D) 9/16-18 3/4-16
Bore (E)
3/32”
1/8”
Nut No.
35HC
326HC
Bushing No. 40HC
366HC
When using these coned connectors, screw the
bushing onto the tube as far as it will go; then insert
the end of the tube into the head or gage block and
tighten the compression nut firmly while holding the
block stationary with the gage facing in the desired
direction. Note that this assembly behaves like a
pipe union, allowing the connecting tube or hose to
remain stationary while the joint is tightened.
Note:
PTFE tape is not required on these connectors.
Tapered Pipe Threads
The pressure gage, needle valves and other fixed
attachments on Parr vessel heads have tapered pipe
threads which are not to be disturbed after they
have been screwed into place. If it becomes neces-
sary to remove any of these fittings, the pipe threads
must be coated with PTFE tape, flexible graphite
tape, or similar luting material on reassembly.
The ID of a pipe or pipe fitting can be enlarged to
accommodate a tubing feed-thru. Note that, in some
cases, this may cause a reduction of the pressure
rating. The port below a female pipe connection can
also be opened up to a larger size.
The maximum openings are shown in the table below.
A
B
C
Tapered Pipe Threads
Nominal Size 1/8”
1/4”
Pipe OD (A)
0.405” 0.540”
Maximum
Feed-thru (B)
1/4”
3/8”
Maximum Exit
Port (C)
0.339” 0.438”
MAINTENANCE
General Maintenance Notes
1. Periodically inspect all electrical wiring and pres-
sure connections for excessive corrosion. Sus-
pect parts should be replaced by components
only supplied by Parr Instrument Company.
2. Always use appropriate wrenches on all fittings
and valves. Never use pliers or pipe wrenches.
3. Head and cylinder service fixtures are available
for convenience and protection of components
during maintenance of your reactor.
Note:
For more information about available
service fixtures, reference TechNote 307.
4. A light coating of thread lubricant, such as Parr
High Temperature Anti-Seize Lubricant, (424HC2)
should be applied to the straight threads of
coned pressure connections as well as to the
nose of the mating piece this will help to obtain
a tight joint.
Note:
PTFE tape should be used only on
all tapered (NPT) threads not NPS straight
threads.
5. NPT (National Pipe Taper) threads should not be
disassembled any more than necessary. It will
become increasingly difficult to maintain a tight
seal with these tapered threads if the joint is
made and broken repeatedly.
6. Do not use oil or anti-seize lubricant on threads
or fittings if the vessel is to be used with oxygen.
7. If your vessel is equipped with a loose compres-
sion ring be sure that it is in place on the head
before attaching any head fittings. The compres-
sion ring cannot be installed after fittings have
been screwed into the head.
8. Clean all threads and gas passages thoroughly
and remove all tape fragments when overhaul-
ing a vessel. An ultrasonic bath is excellent for
cleaning metal parts, but do not place a thermo-
couple probe, pressure gage, face seals or ball
bearings in an ultrasonic bath. Periodic cleaning
may be performed on the exterior surfaces of
the reactor stand with a damp cloth. All power
should be disconnected when cleaning.