Crane duty classification

What is crane duty classification?

Crane duty classification is according to the grades of crane use and crane load condition. Classification principle is in the load, the frequency of different cases, have the same life of the crane at the same level.

Divide crane service class of purpose is not covered, manufacture and selection of users to provide reasonable and unified technical basis and the reference standard, in order to obtain better security, economic effect, make the working status of crane is an accurate reflection of.

It also can improve the generalization level of bộ phận cần cẩu, achieve different lifting weight of crane components work in the same general level of the crane. crane classification is the important basis of crane parts, crane components and component design, is also a security check, accident analysis and scrap the basis of a standard to determine. In general, the duty classification is different, safety factor is different, scrap standard is also different.

Why do you need to confirm crane duty classification when crane buying?

To identify the duty classification of the types of  overhead crane helps you to buy the most suitable overhead cranes for you application, which will be the most economical solution for your application. The right selection of the crane duty cycle or classification will ensure the durability of the overhead crane and components to withstand the loads and usage requirements. Therefore to buy overhead crane, the crane duty classification have to be confirmed.

Two cranes with different duty classifications but with identical capacity and span may vary in price very largely. For high duty classification requires specialized components, such as, electric hoist, end carriage, electric motors, bearings, and crane controls, etc., whereas, the lower duty classification cranes are more standardized and matched with more economical components and parts, which will lower expense to a large degree.

And also you may have a long term plan, that you may expand your production in the future, in this way, your crane capacity may be higher or the number of lifts per day may be increased. In this way, you may want to spec the crane out so that it can support the needs of your future growth.

Factors affect crane duty classification

To select the suitable crane duty class or service class for your crane is very important for it will affect your initial investment and your future maintenance cost required. How to select the crane duty classification for your overhead crane? The following factors should be considered:

• Rated Load – Estimation of the loads lifted at or near capacity
• Service – Total hours in operation per day
• Number of Lifts – Average lifts and trolley and bridge movements made each hour
• Distance – Average length of each movement

Other factors

The following factors do not affect the overhead crane classification directly , but they may affect the crane designing and specifying, which also should be noted.

• Tốc độ – how quickly can the lifting crane transfer materials or equipment? How many lifts per hour can the lifting overhead crane perform?
• Maintenance requirements – will the lifting crane need to be serviced regularly and how will maintenance or repair affect production and downtime?
• Môi trường hoạt động – In what type of environment or conditions will the overhead bridge crane be operating?
• Future needs – Any changes or increases in production requirements down the road? If you design a Class C crane, but know that down the road you be lifting heavier loads or using your crane more frequently, you may need to consider a Class D range crane.

For different countries, the crane duty classifications may vary however they are basicly the same. In the following, the Crane duty classifications from China and USA is presented for your reference.

Crane duty classifications of USA

There are six (6) different classifications for overhead cranes, specified by the Crane Manufacturers Association of America (CMAA). Overhead crane duty classification were established so that the manufacturer and end-user could design the most economical crane for the application, based mostly on the average rated load that the crane will lift, and how often the crane will be performing lifts.
Below we’ll identify and define the six types of overhead crane classes and provide types of businesses or industries that match up the best with each overhead crane classification.

Duty Class A1 (STANDBY SERVICE)

This duty classification covers cranes where precise handling of valuable machinery at slow speeds with long idle periods between lifts is required. Rated loads may be handled for initial installation of machinery and for infrequent maintenance.

Cranes of this duty class are usually used in power houses, public utilities, turbine rooms, nuclear reactor buildings, motor rooms, nuclear fuel handling and transformer stations.

• Bearing Life: 1,250 hours
• Number of Lifts: Up to 2 per hour
• Motor Starts/Stops: 75 per hour

Duty Class  A2 (INFREQUENT USE)

These cranes will be used in installations where the loads are relatively light, the speeds are slow, and a low degree of control accuracy is required. The loads may vary anywhere from no load to full rated load with a frequency of a few lifts per day or month.

Cranes of this duty class are usually used in small maintenance shops, pump rooms, testing laboratories, etc.

• Bearing Life: 1,250 hours
• Number of Lifts: Up to 2 per hour
• Motor Starts/Stops: 75 per hour

Duty Class  B (LIGHT SERVICE)

This duty classification covers cranes where service requirements are light and the speed is slow and loads may vary from no load to occasional full rated loads.

• Average load is 50% of the rated capacity
• 2 to 5 lifts per hour
• Average lift distance of 15 feet
• No more than 50% of the lifts at rated capacity

Cranes of this duty class are usually used in repair shops, light assembly operations, service buildings, light warehousing, etc.

• Bearing Life: 2,500 hours
• Number of Lifts: 2-5 per hour
• Motor Starts/Stops: 75 per hour

Duty Class  C (MODERATE SERVICE)

This duty service class covers cranes where service requirements are deemed moderate.

• Average load is 50% of the rated capacity
• 5 to 10 lifts per hour
• Average lift distance of 15 feet
• No more than 50% of the lifts at rated capacity.

Cranes of this duty service class are usually used in machine shops, paper mill machine rooms, etc.

• Bearing Life: 5,000 hours
• Number of Lifts: 5-10 per hour
• Motor Starts/Stops: 150 per hour

Duty Class D (HEAVY SERVICE)

In this type of duty service class, heavy-duty production is required but with no specific cycle of operations.

• Average loads approaching 50% of the rated capacity will be handled constantly during the work period
• High speeds are desirable for this type of service with 10 to 20 lifts per hour
• Average lift distance of 15 feet
• No more than 65% of the lifts at rated capacity

Cranes of this duty class are usually used in heavy machine shops, foundries, fabricating plants, steel warehouses, container yards, lumber mills, etc., and standard duty bucket and magnet operations where heavy-duty production is required.

• Bearing Life: 10,000 hours
• Number of Lifts: 10-20 per hour
• Motor Starts/Stops: 300 per hour

Duty Class  E (SEVERE SERVICE)

• This type of service requires a crane capable of handling loads approaching the rated capacity continuously, in repetition throughout a stated period per day, in a predetermined cycle of operation.
• Average load at or near the rated capacity
• High speeds are required with 20 or more lifts per hour
• The complete cycle of operation should be specified

Typical examples of this duty class are magnet, bucket, magnet / bucket combination cranes for scrap yards, cement mills, lumber mills, fertilizer plants, container handling, etc.

• Bearing Life: 20,000 hours
• Number of Lifts: 20+ per hour
• Motor Starts/Stops: 600 per hour

Crane duty classifications of China

Crane use levels

Crane use level shows that the crane used frequently during the entire design life, According to the design life period general work cycle number N is divided into ten levels (see table 1).
Table 1:

Crane load condition

Load condition indicates that the degree of the crane load, related to two factors, Namely the ratio of hoisting of the load and the rated load Pi/Pmax, and the ratio of the role of various hoisting load number and the general work cycles ni/N. Indicated the two relations of load spectrum factor　and Kp calculated by type:

Trong công thức:

Kp—load spectrum factorand;
ni—the effect number of load Pi;
N—general work cycles, N= ;
Pi—the I hoisting load, i=1,2….n;
Pmax—max lifting load;
m—index, in here m=3.

Crane load condition according to nominal load spectrum coefficient is divided into four (see table 2)
Table 2:

Crane duty classifications of cranes

Crane duty classification is divided into A1-A8 level. If compare with crane work type China’s regulations in the past, roughly equivalent to: A1-A4 light; A5-A6 middle; A7 heavy; A8 extra heavy.
The following table is the common crane duty classification for overhead crane, gantry crane, jib crane and other types of cranes, etc.

Overhead crane duty classification

For different types of overhead crane, the duty classification is also very different. In the following table, the main ducty classificaiton of overhead crane are presented for  your reference. If you need to buy overhead crane and  to confirm your overhead crane duty classification or duty service classification, please contact loal expert or leave a message below.

Gantry crane duty classification

Cổng trục

Loading bridge crane duty classification

Loading bridge crane

Portal jib crane duty classification

Portal jib crane

Tower crane duty classification

Tower crane

Crawling crane truck crane duty classification

Crawling crane truck crane

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