104
P a r r I n s t r u m e n t C o m p a n y
Stirrer Motors and Drives
Torque vs. Stirring Speed
T
he standard, open-type,
variable speed motor
installed on each Parr reactor
will produce stirring speeds
from zero to between 600
and 800 rpm with a torque
adequate to drive the installed
impellers in average viscosity
mixtures. Higher horsepower
motors and special stirrers can
be provided for higher viscosi-
ties. Alternate drive pulleys are
available to produce higher
stirring speeds, but several
basic rules must be considered
when changing any of these
components.
The highest torque from
any motor
is obtained at lower
stirring speeds. Increasing
the stirring speed reduces the
torque in inverse proportion
to the speed. For operations
involving high viscosity
mixtures, the motor size, the
type of impeller and the stir-
ring speed must be matched
to provide an effective mixing
system.
As a general rule,
the mag-
netic coupling installed on each
Parr reactor will have a torque
rating considerably higher than
the torque obtainable from the
motors offered for use with
that apparatus. The goal is to
make the motor the weak link
so that the magnetic stirrer will
be protected. Reference torque
rating for applicable magnetic
drive.
Explosion Proof Motors
Explosion proof motors
designed for Class I, Groups C
and D and Class II, Groups F
and G with variable speed con-
trol can be furnished for most
Parr reactors.
Air Motors
Air-driven motors can be
installed on most reactors. The
horsepower rating, torque, and
available speed are all depen-
dent upon the pressure and
available volume of the driving
air source. Maximum torques
are delivered at relatively
slow speeds and maximum
horsepower is delivered at high
speed.
Geared, Direct Drive Motors
A geared, direct drive motor
can be installed on most fixed
head floor stand reactors. This
is an attractive arrangement for
handling heavy stirring loads.
Any 1/4 hp or larger,
variable-speed standard or
explosion-proof motor can be
used. Gear box drives are avail-
able with ratios of 3:1, 5:1 and
10:1. The 1700 rpm maximum
speed will be reduced in an
amount determined by the
reduction ratio of the gear
box, and the associated torque
values from the table will be
increased in the same ratio.
Stirrer Drive Motors
Standard Pulley
Optional Pulley
Motor
Designation
HP
Rating
Explosion
Proof
Variable
Speed
Max Speed,
RPM*
Max Torque,
in-lb
Max Speed,
RPM*
Max Torque,
in-lb
-VS.12
1/8
No
Yes
600
12
1700
4
-XP.25
1/4
Yes
Yes
600
27
1700
9
-AM.25**
1/4
Yes
Yes
1000**
30**
—
—
-VS.25
1/4
No
Yes
600
27
1700
9
-VS.50
1/2
No
Yes
600
54
1700
18
-XP.50
1/2
Yes
Yes
600
54
1700
18
-AM.50**
1/2
Yes
Yes
1000**
66**
—
—
-VS.75
3/4
No
Yes
600
81
1700
27
-XP.75
3/4
Yes
Yes
600
81
1700
27
Values represented are nominal.
VS = variable speed, XP = explosion proof, AM = air motor, 1 in-lb = 0.11 Nm, 1 hp = 0.75 Kw
*Maximum speed values based on “no load”
**HP, RPM, and torque values for air motors are based on a 40psi supply capable of 34cfm for the AM.50 and 10cfm for the AM.25.
