Overhead Crane Service Class Selection
Overhead Crane Service Class Selection easy as 1-2-3:
Selecting the correct service class for your overhead crane is usually quite simple.
1)Determine how you are going to use the crane.
a)How much weight will you be picking up.
b) How often you will be picking up the weight
c)How far will it be moved.
The class of crane service can significantly affect the design and the cost of the building framing used for the support of the crane system. The buyer should specify the crant service classification when requesting quotes from crane vendors or general contractors.
CMAA Crane Service Specifications:
1) Service classes have been established to enable the buyer to specify the most economical carrier (trolley) or crane for the particular installation.
To determine proper service classification of equipment, it should be noted that there are three possible basic modes of operation to be considered. They are Crane travel, Carrier (Trolley) travel and Hoist travel. Specific requirements are shown for these components where design is influenced by classifications All classes of cranes are affected by the operating conditions; so for the purpose of these definitions, it is assumed that the crane will be operating in normal ambient temperatures (0°to 100°F) and normal atmospheric conditions (free from excessive dust, moisture and corrosive fumes)
2) Class A
This class is further divided into two subclasses due to the nature of the loads to be handled.
2.1 Class A-1 (Standby Service) – This service class covers cranes used in installations such as power houses, public utilities, turbine rooms, motor rooms and transformer stations, where precise handling of valuable machinery at slow speeds with long idle periods between lifts is required.
2.2 Class A2(Infrequent use) – These cranes will be used in installations such as small maintenance shops, pump rooms, testing laboratories, and similar operations where the loads are relatively light , the speeds are slow and a low degree control accuracy is required. The loads may vary anywhere from no load to full capacity with a frequency of a few lifts per day or month.
3. Class B (Light Service)
This service covers cranes such as those used in repair shops, light assembly operations, service buildings, light warehousing, etc.,where service requirements are light and the speed is slow. Loads may vary from no load to full-rated load with an average load of 50% of capacity with 2 to 5 lifts per hour and averaging 15 feet, with no more than 50% of the lifts at rated capacity.
4. Class C (moderate service)
This service coveres cranes such as those used in machine shops, paper mill machine rooms, etc., where the service requirements are moderate.
In this type of service the crane will handle loads which average 50% of the rated capacity with 5 to 10 lifts per hour and averaging 15 feet, with no more than 50% of the lifts at rated capacity.
5. Class D (heavy Duty)
This service covers cranes, usually cab operated, such as those used in heavy machine shops, foundries, fabricating plants, steel wharehouses,lumber mills, etc., and standard duty bucket and magnet operation where heavy duty production is required but no cycle of operation. Loads approaching 50% of the rated capacity will be handled constantly during the working period. High speeds are desirable for this type of service with 10-20 lifts per hour averaging 15 feet, with no more than 65% of the lifts at rated capacity.
6. Class E&F (Severe Duty & Steel Mill Service)
Cranes in E&F class are covered by the current issue of The Association of Iron and Steel Engineers Standard No. 13for Electric Overhead Travelling Cranes for Steel Mill Service.