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Load Charts & Rigging Certification

2 hours

Learning Objectives

  • •Read a crane load chart to determine rated capacity for a given boom length, radius, and configuration
  • •Explain why load charts are configuration-specific and identify the variables that change capacity
  • •State the OSHA requirement for load chart availability in the operator cab
  • •Apply load-chart principles to determine if a proposed lift is within rated capacity

Topics Covered

  • •Load chart fundamentals: rated capacity is always a function of load radius, boom length, and crane configuration
  • •Load radius: the horizontal distance from the center of rotation to the center of the suspended load
  • •Boom angle and its inverse relationship with load radius — shorter radius = higher capacity
  • •Configuration variables: on rubber vs. on outriggers (fully extended vs. partially extended) vs. on crawlers
  • •Over-front, over-rear, and 360° capacity: structural differences create different capacities by direction
  • •Lattice vs. jib ratings: main boom alone vs. main boom plus jib (fly) sections
  • •OSHA 1926.1417: rated capacity charts must be readily available in the cab at all times
  • •OSHA requirement: if load appears to exceed 75% of rated capacity, operator must confirm actual load weight before proceeding
  • •ASME B30.5: load rating charts must include capacities for all operating radii, boom angles, and work areas
  • •Rigging requirements: all slings, shackles, hooks, and rigging hardware must have documented Working Load Limits (WLL)
  • •Derating factors: dynamic loading from wind, accelerating, or swinging increases effective load beyond static weight
  • •Minimum two full wraps of rope on the drum at maximum hook lowering (OSHA 1926.1417)

Resources

OSHA 1926.1417 — Operation (load chart access and rated capacity)

osha

Required

230 CMR 6.00 — Hoisting Machinery (mass.gov)

regulation

Required

Self-Check Questions

Question 1: A crane's load chart shows a rated capacity of 12 tons at a 30-ft load radius with the boom at 60° on outriggers fully extended. The same chart shows 8 tons at a 40-ft radius. You need to lift a 10-ton load. What must you verify first?

  1. A. That the load weighs no more than 10 tons by estimation
  2. B. The exact horizontal distance from the center of rotation to the load, and that outriggers are fully extended(correct)
  3. C. That the boom angle is at least 60°
  4. D. That you have a qualified rigger on site
Show Explanation

Explanation:

Rated capacity varies directly with load radius. You must measure the actual load radius and confirm the crane is set up in the configuration shown on the chart — in this case, outriggers fully extended. An error in either variable can take the lift beyond rated capacity.

Question 2: Under OSHA 1926.1417, if a crane operator estimates that a load may exceed 75% of the rated capacity, what must the operator do before proceeding?

  1. A. Sound the horn and proceed at half speed
  2. B. Confirm the actual load weight through recognized measurement methods(correct)
  3. C. Get verbal approval from the lift supervisor
  4. D. Reduce boom angle to increase rated capacity
Show Explanation

Explanation:

OSHA 1926.1417 requires the operator to verify the actual load weight through industry-recognized methods before lifting any load that appears to exceed 75% of rated capacity. Estimation alone is not acceptable — the load must be positively identified.

Question 3: What is the minimum number of wire rope wraps that must remain on the hoist drum when the hook is at its lowest point, per OSHA 1926.1417?

  1. A. One wrap
  2. B. Two wraps(correct)
  3. C. Three wraps
  4. D. Five wraps
Show Explanation

Explanation:

OSHA 1926.1417 requires that neither the load line nor the boom hoist line be lowered to fewer than two full wraps remaining on the drum. This ensures the rope end anchor is never subjected to full load, preventing rope pull-out from the drum.

Question 4: A lattice-boom crane load chart shows separate capacity columns for "on outriggers — fully extended" and "on crawlers." You need to lift 15 tons. The chart shows 15 tons is within capacity on outriggers fully extended, but only 10 tons on crawlers. What must you do?

  1. A. Proceed on crawlers since the load is close to capacity
  2. B. Deploy and fully extend the outriggers before making the lift(correct)
  3. C. Reduce boom length to improve the on-crawler rating
  4. D. Lift on crawlers but use a tag line to prevent swinging
Show Explanation

Explanation:

Load chart ratings are configuration-specific. You must set up the crane in the configuration for which the capacity applies — in this case, outriggers fully extended. Operating at 15 tons on crawlers when the crawler rating is only 10 tons is an overload regardless of the outrigger column.

Question 5: Why does a crane's rated capacity decrease as the load radius increases?

  1. A. The wire rope becomes longer and heavier, reducing net capacity
  2. B. The greater radius creates a larger overturning moment, reducing stability(correct)
  3. C. The boom is weaker at lower angles due to compression loading
  4. D. Hydraulic pressure drops at longer extensions
Show Explanation

Explanation:

Rated capacity is governed by the overturning moment, which equals the load multiplied by the horizontal distance (radius) from the tipping fulcrum. As radius increases, the moment increases, requiring a lower rated load to keep the crane stable. Both structural strength and tipping stability are accounted for in the chart.

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