A
ll Parr stirred reactors are
equipped with a magnetic
drive to provide a trouble-free
linkage to an internal stirrer,
thereby avoiding the leakage
problems which can arise with a
packed gland stirrer drive. With
a Parr magnetic drive there are
no rotating seals. The drive turns
freely and the system remains
gas-tight, permitting long,
continuous runs at pressures up
to 5000 psi (345 bar) with little
or no attention to the seal and
drive.
Parr drives are assembled
with specially designed per-
manent magnets which have
excellent temperature stability
and can be depended upon to
operate for long periods with
little or no flux degradation.
Magnets for the inner rotor to
which the stirrer shaft is attached
are enclosed in a stainless steel
(or other alloy) housing, perma-
nently sealed by laser welding
and supported by graphite-filled,
PTFE bushings to provide a long
life, chemically inert stirring
system. Magnets for the outer
drive are also fully enclosed and
supported by twin, high quality
sealed ball bearings for smooth
operation and long life. A water
cooling sleeve attached to each
drive protects the components
from excessive heat arising from
the reactor.
Significant progress was made in recent years in both magnetic
materials and magnetic coupling design. Parr uses neodymium-iron-
boron magnets with 25% more coupling force than samarium-cobalt
magnets. With very few exceptions involving gear reduction drives,
the magnetic stirrers fitted to reactors have higher coupling torques
than the stall conditions of standard motors. Today magnetic drives
are used with confidence for high viscosity polymerization reactions.
Parr magnetic drives are supported with three graphite-filled
PTFE bushings and quality internal ball bearings. They routinely deliver
2000 hours of operation without service.
Four Sizes
Parr magnetic drives are
made in four sizes, designed to
match the full range of Parr reac-
tor sizes and to provide alternate
drives for high viscosity loads,
higher stirring speeds and other
special requirements. Each drive
is assembled in a sealed housing
which threads directly into the
reactor head.
The A1120HC and A1180HC
models are the standard units
normally furnished with the
reactor sizes listed in the adjoin-
ing table. The A1750HC2 model
is a special high torque drive
intended primarily for heavy
loads and high viscosity applica-
tions. When it is used to replace
a standard drive, the standard
motor and drive system may
have to be modified to provide
the higher torque which the
A1750HC2 drive is capable of
transmitting.
14
P a r r I n s t r u m e n t C o m p a n y
High Torque Magnetic Drives
