Topic: 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 classification
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 factorand Kp calculated by type:
Crane load calculating formula
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
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
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
Port jib crane
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
Tower crane
Crawling crane truck crane duty classification
Crawling crane truck crane Hook type A1-A4
Grab bucket A4-A6
Crawling crane truck crane
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:
Types of crane: (Single or double girder? European type or Common one? )
Capacity:
Span:
Height of Lift:
Power supply: (3phase? Voltage? Hz?)
Bay/ Travelling Length:
Quantity:
Operation: Through Pendant/Radio Remote/Cabin Control
Indoor/Outdoor:
Application (What are you planning to lift) :
Environment (Normal/ hazardous) :
Building drawing if possible:
Location:
Industry type: (Eg: Auto, steel, sugar, stone, etc)
Rail Existing/New: (Size in case of Existing)
Number of Cranes in bay:
Existing Structure/New Structure:
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.