Crane duty classification

 Crane duty classification is according to the grades of crane use (in the whole design life cycle total working cycles) and crane load condition, or to say, crane service classifications is that crane heavy degree of parameters, namely that the extent of the crane work on time and hoisting load parameters.

Overhead crane 

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 crane parts, achieve different lifting weight of crane components work in the same general level of the crane. crane manufacturer 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. 

• Speed – 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?
• Operating environment – 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 use level	general work cycle number N	annotation
U0	1.6*10­4	Not often use
U1	2.2*104
U2	3.3*104
U3	1.25*105
U4	2.5*105	Free to use
U5	5*105	Often secondary to use
U6	1*106	Don't always busy to use
U7 U8 U9	2*106 4*106 >4*106	Busy use

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:

In the formula:

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 load condition	nominal load spectrum coefficient (Kp)	Explain
Q1-light Q2-middle Q3-heavy Q4-extra heavy	0.125 0.25 0.5 1.0	Rarely lifting load rating Sometimes lifting load rating Often lifting load rating frequently lifting load rating

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. 

Crane type			duty classification
Overhead crane	Hook type	Power station installation and maintenance	A1-A3
		In workshop and factory	A3-A5
		Heavy work with workshop and warehouse	A6-A7
	Grab type	Discontinuous load and unload	A6-A7
		Continuous load and unload	A8
	Metallurgy type	Used for Lifting work bin	A7-A8
		feed in raw material	A8
		Used for casting	A6-A8
		Used for forging	A7-A8
		Used for quenching	A8
		Used for clamping	A8
		Used for De-cap	A7-A8
		Material rake	A8
		Electromagnet type	A7-A8

Gantry crane duty classification 

Gantry crane	General use hook type	A5-A6
	Loading and unloading with the grab bucket	A7-A8
	Power station with hook type	A2-A3
	Shipbuilding mounting hook type	A4-A5
	Used for container	A6-A8

 

Gantry crane

Loading bridge crane duty classification 

Loading bridge crane	Yard handling with the grab bucket	A7-A8
	Port with the grab bucket	A8
	Port loading and unloading of containers	A6-A8

 

Loading bridge crane 

Portal jib crane duty classification 

Portal jib crane	Installation used hook type	A3-A5
	Hook type used for loading and unloading	A6-A7
	Loading and unloading with the grab bucket	A7-A8

 

Portal jib crane 

Tower crane duty classification 

Tower crane	General construction and installation	A2-A4
	With bucket loading and unloading of concrete	A4-A6

 

Tower crane

Crawling crane truck crane duty classification 

Crawling crane truck crane	Hook type	A1-A4
	Grab bucket	A4-A6

 

Crawling crane truck crane

Get right crane duty for your crane

In order to give you suitable crane solution and specific crane price promptly, please help our crane engineer to confirm the following information as much as possible:

1. Types of crane: (Single or double girder? European type or Common one? )
2. Capacity:
3. Span:
4. Height of Lift:
5. Power supply: (3phase? Voltage? Hz?)
6. Bay/ Travelling Length:
7. Quantity:
8. Operation: Through Pendant/Radio Remote/Cabin Control
9. Indoor/Outdoor:
10. Application (What are you planning to lift) :
11. Environment (Normal/ hazardous) :
12. Building drawing if possible:
13. Location:
14. Industry type: (Eg: Auto, steel, sugar, stone, etc)
15. Rail Existing/New: (Size in case of Existing)
16. Number of Cranes in bay:
17. Existing Structure/New Structure:
18. Your full company address and contact details:

If you do not know about how to select the crane, please feel free to leave us a message or email to sales@cranesdq.com. The reply of our crane engineer will be given within 24 hours. Get your custom design crane.

Crane duty classification