OSHA Pre-Lift Planning & Load Chart Interpretation 2 — Questions and Answers
Question 1: What does 'derating' a crane mean in pre-lift planning?
- Increasing the crane's rated capacity for special lifts
- Reducing the rated capacity due to site conditions such as ground stability or wind (Correct answer)
- Removing the crane from service permanently
- Switching to a lower boom angle
Correct answer: Reducing the rated capacity due to site conditions such as ground stability or wind
Derating means applying a reduction factor to the crane's chart capacity to account for adverse conditions like soft ground, wind, or blocked outriggers.
Question 2: Which ground condition requires additional engineering evaluation before positioning outriggers?
- Dry, compacted gravel
- Freshly placed concrete
- Soil over underground utilities or voids (Correct answer)
- Asphalt pavement in summer heat
Correct answer: Soil over underground utilities or voids
Soil over underground utilities, tunnels, or voids may collapse under outrigger loads and requires engineering evaluation of bearing capacity.
Question 3: A lift plan calls for a 40-ton load at a 30-foot radius. The load chart shows a 45-ton capacity at that radius. What is the load line percentage?
- 67%
- 75%
- 89% (Correct answer)
- 93%
Correct answer: 89%
40 tons ÷ 45 tons × 100 = 88.9%, approximately 89% of rated capacity, which qualifies as a critical lift.
Question 4: When must a crane operator refuse to make a lift?
- When the load is above 50% of rated capacity
- When the load weight is unknown or exceeds rated capacity (Correct answer)
- When the lift requires a tagline
- When the lift takes longer than 30 minutes
Correct answer: When the load weight is unknown or exceeds rated capacity
OSHA requires operators to refuse any lift where the load weight is unknown or where the load would exceed the crane's rated capacity.
Question 5: What is the purpose of outrigger pads (cribbing) during a crane setup?
- To increase the crane's swing speed
- To distribute the outrigger point load over a larger soil area and prevent punch-through (Correct answer)
- To protect the outrigger cylinders from corrosion
- To level the crane when the ground slope exceeds 5 degrees
Correct answer: To distribute the outrigger point load over a larger soil area and prevent punch-through
Outrigger pads spread the concentrated load from the outrigger float across a larger surface area, reducing ground pressure and preventing sinkage.
Question 6: In a pre-lift plan, the 'pick radius' differs from the 'set radius' when:
- The load will be lifted and swung to a different location at a different distance from the crane (Correct answer)
- The load is symmetrical
- Only one crane is used
- The load weighs less than 1,000 lbs
Correct answer: The load will be lifted and swung to a different location at a different distance from the crane
Pick radius is where the load originates and set radius is where it is placed; if they differ, the operator must verify rated capacity at both radii.
OSHA Pre-Lift Planning & Load Chart Interpretation 2
What does 'derating' a crane mean in pre-lift planning?