122
P a r r I n s t r u m e n t C o m p a n y
Insulated Electrical Glands
Temperature Limits
Spare Parts Kits
T
here are a number of fac-
tors that determine the
maximum temperature rating
of a pressure vessel. For most
applications it is the gasket
material. Vessels with O-ring
seals are limited to 225 °C
unless exotic materials are
used to extend this tempera-
ture to 275 °C. Parr’s design
for contained PTFE gaskets
extends the operating
temperature range to 350
°C. Flexible Graphite (FG)
material essentially removes
the gasket as the limiting
factor. Maximum temperature
limits for the metals used in
these vessels are established
by ASME code and other
standards. Most metals have
maximum temperature limits
between 400 and 800 °C. The
allowable strength for these
metals falls off rapidly as they
reach maximum operating
temperature. Finally, the
difficulties encountered with
screw threads and other clo-
sure components operating at
high temperatures establish a
practical temperature limit for
externally heated vessels. We
have found 600 °C to be
a reasonable limit.
Internally Heated Vessels
Exposed Heaters.
Another
approach has proven useful in
extending the maximum tem-
perature limit. In this design
the heater or furnace is placed
inside the pressure vessel. The
heater is surrounded by a layer
of insulation. This creates a
hot zone in the center of the
vessel and prevents the walls
from exceeding their allow-
able limit. Properly designed,
temperatures as high as 1200
°C can be achieved in the core
of the vessel while the walls
remain below 250 °C. This
system is very energy efficient.
Internal heaters can be less
E
ach stirred reactor is fur-
nished with a set of spare
parts and fittings including a
6-foot gas supply hose, head
gaskets, rupture discs, and a
set of replacement parts for
the stirrer drive.
A reserve supply kit of
spare parts can be ordered
from Parr Technical Service
to provide sufficient parts and
tools to handle most normal
replacements and emergency
repairs during the first year
A
variety of insulated electri-
cal leads can be installed
in any Parr reactor or pressure
vessel for electrical measure-
ments or to supply power to
an internal heater or other
devices. Three different gland
designs are available. These
screw into a vessel and will
have pressure and tempera-
ture ratings to match those of
the vessel in which they will
be used.
Transducer Glands
Transducer glands are used
for applications requiring a
number of small insulated
wires in a single gland. Wire
sizes from 14 to 24 gage are
used to carry small currents
and voltages in the millivolt
range. A unique feature of this
design is that multiple wires
(up to 16) can be individually
insulated through a single
gland.
Electrode Glands
Applications requiring a
single electrical conductor
with current carrying capaci-
ties from 20 to 100 amperes
and voltage ratings to 2000
volts can be handled with an
electrode gland. These glands
have a single conductor (or
electrode) in sizes from 0.093
to 0.312-inches in diameter,
with the ends of the conductor
threaded so that internal and
external lead wires can easily
be attached.
Power Leads
Power leads can be provided
with either single or multiple
flexible wires in sizes from 14
to 18 gage. Current ratings
range from 5 to 20 amperes at
up to 600 volts. Either PTFE or
ceramic insulation is available.
Ceramic glands can be used
to the full temperature rating
of any Parr vessel. Pressure
ratings will vary from 1000 to
10000 psi, depending upon the
design of the gland, its size and
the type of insulation used.
Miscellaneous Sensors
Parr has installed a number
of different sensors in its
various reactors and pres-
sure vessels, including both
single point and continuous
liquid level sensors, pH elec-
trodes and dissolved oxygen
electrodes. Each of these
installations must be carefully
developed in consultation
with the user, the electrode
or probe supplier and the
Parr Engineering Department.
Glass electrodes with O-ring
seals will carry rather severe
temperature and pressure
restrictions. There are also
space restrictions which gener-
ally dictate that accessories of
this type can only be installed
in 1000 mL or larger vessels.
of heavy usage. These kits
include replacement gaskets,
O-rings, rupture discs, drive
belts, and seals. These kits are
a convenient package of the
small perishable items required
for normal maintenance of the
reactor.
When ordering any kit for an
existing reactor please specify
the preferred gasket/seal mate-
rial, the range of the rupture
disc, material of the reactor,
and the length of the drive belt.
