Consider the following statements regarding the dependency of crane load capacity : 1. The size of the crawlers is not a factor due to diminutive mounting which decreases the stability of any footing. 2. The strength of the boom is also one of the major governing factors in establishing load ratings, and any extension of the boom reduces the rating. Lowering the boom also increases the clearance radius and thus reduces the rated capacity. 3. The counterweight is added to the after-end of the machine. Manufacturer’s specifications provided standard and maximum counterweights and also the crane ratings. Counter weights may be increased to a specified maximum, but the operating radius must not exceed that given by the manufacturer. Which of the above statements is/are correct ?
- A1 and 2
- B1 and 3
- C1 only
- D2 and 3Correct
Solution
Concept
Factors governing the rated load of a crane
Step-by-step solution
1. The size of the crawlers does affect stability and hence the rating (statement 1 false). 2. The boom strength and its length/radius govern the rated load (statement 2 true). 3. The counterweight increases the stable load, within the manufacturer's limits (statement 3 true).
Explanation
Crane capacity depends on stability (crawler or outrigger size, counterweight) and on the strength of the boom.
Why the other options are wrong
Statement 1 denies the effect of crawler size, which is wrong.
Shortcut
Crane rating = f(boom, radius, counterweight, base).
Common mistake
Accepting statement 1.
Correct answer: D) 2 and 3