Overhead Crane Classification

Determine the proper CMAA classification for your crane:

Having been in the crane industry for more than 30 years, I have noticed that a reoccurring  problem I encounter on a daily basis is the determination of the CMAA classification of a particular crane. The problem lies in the broad wording used in the classification charts as well as an end user, builder and even some crane sales persons I have encountered just making a determination without even looking at the specification charts and true application.
The proper determination is crucial to the correct crane being specified for each application. In the current state of our industry, this is becoming even more critical as crane manufactures are engineering all their components to much tighter specifications in order to be cost competitive. Today,components are no longer being over built and almost everything is built to the specification required. Thus the proper classification is extremely important in today’s crane world.
I came across this simple way to determine the specification necessary years ago and still implementing this strategy today. While in some of the higher specifications further examination may be necessary but this will get you pretty close in almost any situation. It is based on a points system and pretty self explanatory. You go through each area and make the proper number selection and then add them all up and use the matrix to determine your classification. The key here is to be honest in the application, there is no use in cutting corners as you might as well just be pulling it out of the sky again!

1. Operating Factor

  • The first factor is the operating factor. How often will the crane be used? Is it for stand-by or maintenance service? Is it for 2,000 hours per year or less, which is the one shift operation, 4,000 hours per year, which is the 2 shift operation, or the 6,000 hours per year, which is the three shift operation
  • POINTS
  • Stand-By or Maintenance 5
  • 2000 Hours/Year or less (1 Shift) 8
  • 4000 Hours/Year or less (2 Shifts) 15
  • 6000 Hours/Year or less (3 Shifts) 25

 

2. Relative Load Factor

  • The next factor to consider is the relative load factor. How does the average lifted load compare to the rated capacity of the crane?
  • Several loads per week at rated capacity 5
  • Several loads per day at rated capacity 15
  • (Majority of loads less than 50% of rated capacity)
  • Several loads per day at rated capacity 25
  • (Majority of loads greater than 50% of rated capacity)
  • Frequent capacity loads per day 35
  • (Majority of loads greater than 50% of rated capacity)

3. Load Impact Factor

  • The load impact factor considers the relative severity of the cranes operation. Is the service low and smooth as in a powerhouse operation? Will the crane be subject to the high impact forces inherent in magnet/bucket service found in steel mills or cement mills? Or does the service fall somewhere in between?
  • Stand-by, Maintenance, Powerhouse 5
  • Warehouse, Machine Shop, Assembly Shop 8
  • Foundry, Hot Metal 15
  • Bucket, Magnet, Grapple 25

4. Relative loss factor (Downtime)

  • The relative loss factor is a measure of the importance of the crane to your operation. If the crane is down for unscheduled maintenance, what is the effect; an inconvenience, a slowdown of operations, or a plant shutdown?
  • Low value on downtime (Inconvenience) 5
  • Medium value on downtime (Slowdown of operation) 15
  • High value on down time (Plant shutdown) 25

5. Ambient Temperature and Environmental Factor

  • Are the ambient temperatures extremely high or low? Or is there a combination of these conditions affecting the crane? The A and E factor considers where the crane is located. Is the environment normal, corrosive or highly contaminated?
  • Normal Indoor or Outdoor Service 5
  • Corrosive, Highly Contaminated Area, or Temperature Extremes 10
  • Corrosive and Highly Contaminated Area 15

6. Maintenance Factor

  • The last factor to consider is the Maintenance factor. While a true preventive maintenance program is ideal, it is very seldom the case.
  • Preventive Maintenance Program 5
  • Normal Maintenance Handled by Maintenance Department but
  • Reactionary other than Lube and minor adjustments 15
  • No In-House Maintenance Capabilities 25
  • This is where you need to add up your points and see where you fall in the matrix key.
  • 0 to 40 Points = CMAA Class “A” and “B”
  • 41 to 65 Points= CMAA Class “C”
  • 66 to 85 Points= CMAA Class “D”
  • 86 to 115 Points= CMAA Class “E”
  • 116 to 150 Points= CMAA Class “F”

I have found over the years there are two areas overlooked or misunderstood the most when determining the classification, the relative loss factor and the Maintenance Factor. If you use this and understand it, it will save you time and possibly money in the future by specifying the correct crane for the application.

 

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