102
P a r r I n s t r u m e n t C o m p a n y
Heaters
P
arr has designed standard
electrical heaters for all
of the reactors in our product
line. Different types of heaters
are used for individual reactors
to best meet the operational
needs, heating load, and
expected operating tem-
peratures. The standard heater
type and power rating for each
reactor model is listed in the
reactor specification tables.
The standard designs will typi-
cally be one of the following:
Clamp-On Band Heaters
These are normally used
for very small reactors where
maximum watt densities and
heat transfer are required due
to the limited surface area
available on the vessel.
Rigid Heating Mantles.
These are quartz fabric
mantles housed in aluminum
shells. They are used for
moderate sized reactors in
designs where the heater can
be moved on or off the vessel.
They are light weight and easy
to handle, but they are not
used to support the weight
of the vessel and they are
generally limited to operating
temperatures of 350 °C or less.
Calrod-Type Sheathed
Element Heaters.
These are rugged heaters
with Calrod-type elements
held within a metal shell. They
are used for medium to large
reactors for operating temper-
atures to 350 °C. In some cases
the heater shell itself forms a
part of the reactor support. An
advantage of Calrod heaters is
that the heating elements are
easily replaceable.
Ceramic Heaters.
These are special purpose
heaters with an electric ele-
ment embedded in a shaped
ceramic body which is held
within an insulated metal
housing. They are used for
reactors designed for tempera-
tures to 600 °C and for large
multi-zone heaters.
Optional and Custom
Heaters.
Parr offers a variety of
heater designs which can be
substituted for the standard
heater normally furnished with
each reactor. Most of these
can also be used with Parr
non-stirred pressure vessels
as well. The principal features
and recommended applica-
tions for these heaters are
described below.
Flexible Heating Mantles.
These can be furnished for
many different applications.
These are similar to the rigid
type described above except
they are not held in an alu-
minum housing. They have a
flexible fabric outer case for
electrical and thermal insula-
tion. This type of mantle is
particularly useful for heating
vessels with irregular shapes,
such as those with windows
in the cylinder wall, since they
are flexible and can be split
and laced onto a vessel around
any external protrusion. As
with rigid mantles, they will
produce temperatures up to
350 °C, but they are limited
to watt densities of 10 watts
per square inch. This type of
heater can be made to cover
any of the vessels offered by
Parr, and they are sometimes
preferred when only moderate
temperatures are required.
Since they are constructed of
cloth, an electrical ground wire
cannot be provided.
Aluminum Block Heaters.
These are available as an
option for most reactors and
pressure vessels. For vessels
of two gallons or less the
heaters are machined from
solid blocks of aluminum and
heater wells are machined into
the walls of the block. Optional
cooling channels are also
included.
Aluminum block heaters
have three distinct features
which make them ideal for
many applications:
1. Since the heating elements
are sealed within these
housings, explosive vapors
cannot reach them and the
heater can be considered
explosion proof, provided
it is equipped with optional
explosion proof wiring and
a safety cut-out to ensure
that the heater will not
exceed a specified tempera-
ture limit allowed for the
explosive atmosphere.
2. With heat spread uniformly
throughout the aluminum
block, uniform heating is
applied to all surfaces of
the vessel, comparable to
the rapid response obtained
with a steam or hot oil
jacket, but without requiring
costly steam generators, oil
baths, circulating pumps
and other accessory equip-
ment.
3. Since there is a cooling
coil in the aluminum block,
this style heater can also
provide external cooling
for controlling an exother-
mic reaction without the
internal clutter and clean-
ing problems associated
with internal cooling coils.
Eliminating an internal coil
also permits the use of spi-
ral, paddle or other stirrers
which cannot be used when
an internal coil is installed.
Circulation Jackets.
A jacket can be welded to
the outer wall of most Parr
pressure vessels to provide a
means for heating or cooling
the vessel with a hot or cold
liquid or steam. This type
of heating is ideal for users
who want to duplicate plant
operating conditions, using a
jacketed reactor comparable
