Crane Hoist Duty Classification

In the process of purchasing a crane, the business manager usually asks some questions such as:

1.How many hours the cranes will be used per day? by average level
2.How many lifting times per hour by average level? etc.

These questions are prepared for the selection of cranes. Through these questions, the sales manager selects the corresponding crane solution. You will get a crane quotation with work duty marked as A5/M5, A3/M3, etc. Maybe you will be very curious about what these grades represent? Today, we will elaborate on what the work duty of the crane hoisting is, what it affects, and how to calculate and select the appropriate crane working duty.

What Is Crane Hoist Duty Classification?

Crane hoist duty classification helps determine how often and how heavily a crane can be safely used. It ensures:

Longer equipment life – Prevents overloading and wear
Better safety – Reduces breakdowns and accidents
Cost efficiency – Matches the right crane to the job

The classification depends on two main factors:

Load Spectrum – How heavy the loads are (Light to Very Heavy)
Daily Operating Time (Usage Time)– How many hours the crane works per day

How to Determine the Load Spectrum

The load spectrum is based on how much weight the crane lifts regularly:

Classification	Load Type	Typical Use Case
Light (M3/1Bm)	Mostly light loads, occasional full load	Warehouses, small workshops
Medium (M4/1Am)	Mix of light and medium loads	Construction sites, factories
Heavy (M5/2m)	Frequent full loads, heavy use	Steel plants, shipyards
Very Heavy (M6+/3m+)	Almost always full loads	Mining, heavy industry

Calculating Daily Operating Time

The formula to find the average daily operating time is:

t = (2 × N ×H × T) / (V × 60)

Where:

N = Work cycles per hour (e.g., 5 lifts/hour)
H = Average lifting height (meters)
T = Daily working hours (e.g., 8-hour shift)
V = Hoisting speed (meters per minute)

Example Calculation:

If there is a crane which load spectrum is heavy, a crane lifts 5 times/hour (N=5), average height (H=3m), works 16 hours/day (T=16), and speed (V=5 m/min):

t=(2×5×3×16) / (5×60)=1.6 hours/dayt=5×602×5×3×16=1.6 hours/day

This means the crane’s duty class is M5 (GB A5 / FEM 2m).

International Duty Class Comparison

Different countries use different codes:

ISO/BS/DIN	China (GB)	Europe (FEM)	USA (CMAA)
M3	A3	1Bm	A
M4	A4	1Am	B
M5	A5	2m	C
M6	A6	3m	D

Why Does Duty Classification Matter?

Safety compliance – Avoid fines and accidents
Better maintenance planning – Know when to service the crane
Cost savings – Don’t buy an over-spec crane for light jobs

3 Tips to Choose the Right Class

Choosing the right crane duty class ensures safety, efficiency, and cost savings. Always check:

Check Loads (load spectrum): how heavy the loads are (use our load chart).
Count Hours (Daily operating time): how long the crane works.
Match to Our Models(International standards): See our Duty Class Guide PDF for quick picks.

📥 Complete Technical Resource [Download the Crane Duty Class Calculator & Standards Handbook(PDF)]

Crane Duty Class Calculator & Standards Handbook Download

For more details, check official standards like FEM 9.511 or GB/T 3811.