De-mystifying technical specifications (part 2): Hoist & motor duty cycle

What is ‘Ingress Protection’ rating?

You are buying that hoist or crane and in the specifications on your quotes you are confronted with a selection of random numbers and letters that are supposed to inform you of the duty cycle of your hoist. Hoist and motor duty cycles are noted in different ways as recognised by the various authorities that govern the industry.

 

Duty Cycle: Motors

In regard to motors, you have an “ED” rating prefixed by a percentile figure. ED stands for “Einschaltdauer”, which is translated as duty cycle. ED ratings work on a 10-minute operating time that includes a cool-off time. For example, if a motor has a 40% ED, this means that the motor can operate for 4 minutes (40% of 10 minutes), with 6 minutes of cooling time. The cooling time returns the motor to an efficient working temperature before it is ready for the next cycle.

 

Duty Cycle: Hoists

Hoist ratings are typically expressed as follows:

 

2m/M5

The first portion is the FEM rating and the second is the ISO rating. FEM is the European Federation of Materials Handling, and, like ISO (International Organization for Standards), is responsible for publishing standards with the goal of establishing a certain lifespan for a crane or hoist (typically 10 years).

The below table illustrates the framework around which these standards are classified when it comes to your new hoist or crane:

 

Average Daily Operating Time
ISO/FEM
(hours per day)
Load Spectrum ≤0.5 ≤1 ≤2 ≤4 ≤8 ≤16
Light M3
1Bm
M4
1Am
M5
2m
M6
3m
Medium M3
1Bm
M4
1Am
M5
2m
M6
3m
M7
4m
Heavy M3
1Bm
M4
1Am
M5
2m
M6
3m
M7
4m
Very Heavy M4
1Am
M5
2m
M6
3m
M7
4m

 

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