Selection of the proper clutch, brake, or clutch-brake is relatively simple if certain rules are followed (see table below). For occasional start or stop applications where the load is light and the cyclic rate is under 20 cpm, the selection steps are:
- Determine hp and rpm requirements
- Calculate torque requirements
- Select the unit based on hp, rpm, and torque
Manufacturers' catalogs provide torque versus air pressure charts or selection tables to assist in the selection process. These charts have a service factor built in.
Energy capacity of a friction facing is determined by the material and based on the available volume of friction material and its wear rate. Life expectancy is determined by dividing the friction facing's energy capacity by the energy used per cycle. Energy capacity, rotational inertia, energy per cycle, rate of engagement, and other specifications are found in manufacturers' catalogs.
Clutch and brake thermal horsepower ratings are also an important consideration in the selection process. Thermal horsepower is an indication of a unit's ability to dissipate heat. Dissipating frictional heat increases life expectancy. Low inertia and cycle rates also increase friction facing and disk life. Low speed reduces thermal horsepower, but detracts from a unit's ability to cool by windage. To obtain satisfactory life from a clutch or brake, the thermal horsepower to be dissipated should be less than the thermal horsepower rating.
How to Select a Clutch
Clutch and Brake Selection Guidelines
| Application |
Function |
Selection
Considerations |
Suggested
Clutches and Brakes |
- Occasional start and stop
|
|
|
- Single disk clutch and brake
- Diaphragm brake
- Tooth clutch
|
|
- Accurate positioning
- Reversing multiple speeds
- Inching and jogging
- Indexing
- Coupling
|
- Torque response time
- Cycle rate
- Inertia
- Thermal capacity
- RPM
|
- Single disk clutch
- Tooth clutch
- NEMA C clutch and brake
|
- High inertia start or stop
|
- Controlled acceleration
- Controlled deceleration
- Emergency stop
|
- Torque
- Thermal capacity
- RPM
- Inertia
|
- Single or multi-disk clutch
- Spring engaged brake
- Caliper brake
|
- Continuous slip or constant tension
|
- Tension control: unwind/rewind
|
- Heat dissipation
- Line speed
- Roll and core diameter
- Web width
|
- Caliper brake
- Single disk clutch and brake
- Drum brake
|
For more information contact:
Technical Support
(800) 843-7445
info@nexengroup.com
|
