Brochure

87
OverloadServiceFactors
Load and operating characteristics of both the driving and driven units
must be considered thoroughly in the selection of Browning Gripbelt
®
Drives. It is essential that all drives be designed for maximum load
conditions to be encountered.
Most drives will at some time be overloaded, perhaps only momentarily.
It is good practice to have predetermined drive capacity to handle this
overload. This predetermined drive capacity helps protect against
breakdowns due to premature belt failure. The use of an extra belt
will pay for itself many times over by increasing the life of all the belts
more than the proportionate cost of the extra belt.
For good design and satisfactory drive life all drives must be selected
giving careful consideration to two fundamental conditions:
1. The motor must have greater capacity than the driven unit.
2. The drive must have greater capacity than the motor.
Careful consideration of Overload Service Factors for various types
of driven units, drivers, type of starting, frequency of maintenance
and other drive conditions is extremely important for satisfactory
performance and life.
The following are suggested Overload Service Factors for various
typical driven units:
TableNo.1 SuggestedOverloadServiceFactorsforTypicalApplications
A minimum Service Factor of 2.0 is suggested for equipment subject to choking.*
Service factor should be increased by 0.2 on drive units with an increaser drive speed of 2200 rmp or lower when using a 1750 rpm motor. This is
a speed-up ratio of 1.25 or less. For speed increaser drives or speed-up drives greater than 2200 rpm, the recommendation is to use a 2.0 service
factor.
CAUTION: Drives requiring high Overload Service Factors, such as crushing machinery, certain reciprocating
compressors, etc. subjected to heavy shock load without suitable fly wheels, may need heavy duty web type sheaves
rather than standard arm type. For any such application, consult Application Engineering.
TYPES OF DRIVEN MACHINES
TYPES OF DRIVING UNITS
AC Motors; Normal Torque, Squirrel
Cage, Synchronous and Split Phase.
DC Motors; Shunt Wound. Multiple
Cylinder Internal Combustion Engines.
AC Motors; High Torque, High Slip,
Repulsion-Induction, Single Phase,
Series Wound and Slip Ring.
DC Motors; Series Wound and
Compound Wound. Single Cylinder
Internal Combustion Engines.
Clutches.Line Shafts.
Intermittent
Service (3-5
Hours Daily or
Seasonal)
Normal
Service (8-10
Hours Daily)
Continuous
Service (16-24
Hours Daily)
Intermittent
Service (3-5
Hours Daily or
Seasonal)
Normal
Service (8-10
Hours Daily)
Continuous
Service (16-24
Hours Daily)
Agitators for Liquids
Blowers and Exhausters
Centrifugal Pumps and Compressors
Fans up to 10 hp
Light Duty Conveyors
1 1.1 1.2 1.1 1.2 1.3
Belt Conveyors for Sand, Grain, etc.
Dough Mixers
Fans Over 10 hp
Generators
Line Shafts
Laundry Machinery
Machine Tools
Punches-Presses-Shears
Printing Machinery
Positive Displacement Rotary Pumps
Revolving and Vibrating Screens
Speed Reducers, All Types
1.1 1.2 1.3 1.2 1.3 1.4
Brick Machinery
Bucket Elevators
Exciters
Piston Compressors
Conveyors (Drag-Pan-Screw)
Hammer Mills
Paper Mill Beaters
Piston Pumps
Positive Displacement Blowers
Pulverizers
Saw Mill and Woodworking Machinery
Textile Machinery
1.2 1.3 1.4 1.4 1.5 1.6
Crushers (Gyratory-Jaw-Roll)
Mills (Ball-Rod-Tube)
Hoists
Rubber Calenders-Extruders-Mills
1.3 1.4 1.5 1.5 1.6 1.8