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The main technical parameters of overhead cranes are lifting capacity, span, lifting height, running speed, lifting speed, type of work and motor energization duration rate.

Lifting capacity 
Lifting capacity, also known as the rated lifting capacity, is the crane's actual permissible lifting the maximum load, in tons (t) for the unit.
Overhead crane lifting capacity of 5, 10 (single hook), 15/3, 20/5, 30/5, 50/lO, 75/20, 100/20, 125/20, 150/30, 200/30, 250/30t (double hook) and so on. The numerator in the figure is the main hook lifting capacity, and the denominator is the secondary hook lifting capacity. Such as 15t/3t crane is the main hook rated lifting capacity of 15t, the rated lifting capacity of the secondary hook for 3t.
Overhead cranes can be divided into three levels according to the lifting capacity, 5 ~ lOt for small cranes, lO ~ 50t for medium-sized cranes, more than 50t for heavy-duty cranes.

Span
The span of the overhead crane is the distance between the center lines of the wheels at both ends of the crane beam, i.e., the distance between the center lines of the big car tracks, in meters (m).
Bridge crane span 10.5, 13.5, 16.5, 19.5, 22.5, 25.5, 28.5, 31.5m and so on. Every 3m for a level.
Lifting height
Crane spreader or gripping device (such as grabs, electromagnetic suction cups) of the upper limit position and the distance between the lower limit position, known as the crane lifting height, in meters (m) for the unit.
Cranes generally commonly used lifting height of 12, 16, 12/14, 12/18, 16/18, 19/21, 20/22, 21/23, 22/26, 24/26m and so on. Where the numerator is the main hook lifting height, the denominator is the secondary hook lifting height.

Running speed
Running speed refers to the large and small car moving mechanism in its dragging motor to the rated speed when the corresponding speed, in meters / minutes ( m / min ) for the unit. The running speed of small car is generally 40~60m/min, and the running speed of large car is generally 100~135m/min.

Lifting speed
The motor of the lifting mechanism rises the weight at the rated speed, i.e. the lifting speed. Generally, the lifting speed does not exceed 30m/min, depending on the nature of the weight, weight, lifting requirements to decide.
Lifting speed and empty hook speed, empty hook speed can shorten the non-productive time, empty hook speed can be as high as twice the rated lifting speed.
There is a special case of lifting speed, the low speed when the weight is close to the ground, called landing low speed, to ensure personal safety and cargo safety, its speed is generally 4~6 m/min.

Type of work
The type of work of the crane is determined by its load rate and the busy degree of work, which can be divided into four types: light, medium, heavy and extra heavy.
(1) Light grade. Low operating speed, less use? Less chance of full load, energized sustained rate of 15%. Used in unstressed and not heavy workplaces. Such as in the hydropower station, power plant used as a crane for installation and maintenance.
(2) Intermediate. Often work under different loads, medium speed, the work is not too heavy, energized sustained rate of 25%, such as general machining shop and assembly workshop with the crane.
(3) Heavy grade. Heavy work, often work under heavy load, energized sustained rate of 40%, such as metallurgy and foundry cranes used in the workshop.
(4) Extra heavy grade. Often hanging rated load, work is particularly busy, energized sustained rate of 60%, such as metallurgy special bridge crane.
Continuous rate of energization
Bridge crane motor in a work cycle is intermittent work, the work of the heavy degree of power continuity rate JC% said. Energized sustained rate for the working time and the percentage of the working cycle