Trolleys are used with electric hoists and enable the hoists to move on a track. Trolleys can be distinguished by the following attributes:
- Load capacity: Measured in pounds force or tons.
- Beam height and width: The height and width of the beam to which the hoist will be affixed.
Items to consider when selecting a hoist:
- Weight of load
- Power supply
- Speed of lifts
- Lifting height
- Frequency of lifts
- Duty cycle
The powered hoist industry uses a service classification system to help you select the proper hoist. See the chart below for details.
Electric Hoist Service Classifications
|SERVICE CLASSIFICATION||TOTAL EQUIPMENT RUNNING TIME||MAX. START/STOPS |
|TYPICAL AREAS OF APPLICATION|
|H4 ||Approaching 50% of the work period||300||High-volume handling in steel warehousing, machine shops, fabricating plants, mills and foundries. Manual or automatic cycling operations in heat-treating and plating operations.|
|H3||Not to exceed 25% of the work period||150||General machine shop, fabricating, assembly, storage and warehousing use, where loads and operation are randomly distributed.|
|H2||Not to exceed 15% of the work period||75||Light machine shop, fabricating industries, and service and maintenance work, where loads and use are randomly distributed with capacity loads infrequently handled.|
How to Choose What Service Classification You Need
Determine the maximum weight you need to lift. (Include lifting, supporting and positioning devices.)
Ex: 2400 lbs. (includes pallet, drum, sling, etc.)
What is the nominal voltage (±10% of rated voltage) in your facility? (Single-phase 115 or 230V; 3-phase 208, 230 or 460V)
What speed do you want to lift the load? Industry standard for 1/8 to 1 ton is 16 ft./min. (fpm); 2 tons is 8 fpm. For flexibility, consider a variable speed lift.
Ex: 8 fpm
Measure from the point of mount to the floor.
Ex: 12 ft.
What is the actual distance the load must be lifted and lowered?
Ex: 7 ft.
Determine the number of lifts per hour for the job.
How many times does an operator activate the push-button control? Rule of thumb: 8 start/stops per cycle (load lift and lower).
Ex: 120 start/stops
Hoists have a Service Classification rating. To determine the classification for your job, see the calculations below:
Ex: 12 ft.
Once a % On Time is determined, see the Electric Hoist Service Classifications to determine the hoist needed.
Selected hoist in this example should offer 2-ton capacity, 230V, 3-phase operation, 15-ft. lift, 8 fpm and have a 44% or H4 service classification. Example is based on having nominal voltage and 80°F ambient still air. Higher temperatures and/or voltages outside of nominal range will result in reduced duty cycles.