Load Restrictions
1.5 hours
Learning Objectives
- •Read and interpret a telescoping boom truck load chart
- •Explain how radius, boom angle, and extension affect rated capacity
- •Identify the consequences of exceeding rated load limits under MA law
- •Describe how outrigger position affects the applicable load chart section
Topics Covered
- •ASME B30.5 rated capacity: the maximum load at a given radius and configuration
- •Load chart sections: over-end vs. over-side capacities
- •Gross vs. net capacity: deducting the weight of rigging and headache ball
- •Radius: measured horizontally from center of rotation to load center
- •Boom angle and length: how extending the boom increases radius and reduces capacity
- •Two-blocking: boom tip block contacts headache ball — immediate shutdown required
- •Anti-two-block (ATB) devices: required on telescoping booms by ASME B30.5
- •Outrigger deployment: fully extended vs. partially extended changes which chart to use
- •Outrigger float contact: all floats must bear on firm, level ground
- •Side loading: telescoping booms are not designed for side loading
- •MGL §65 — operator must not exceed rated capacity under any circumstance
Resources
Self-Check Questions
Question 1: A boom truck load chart shows 8,000 lbs capacity at 20 ft radius. You plan to lift a 7,500 lb load with 600 lbs of rigging. Can you make the lift at 20 ft radius?
- A. Yes — 7,500 lbs is under the 8,000 lb chart limit
- B. No — the total load including rigging is 8,100 lbs, which exceeds rated capacity(correct)
- C. Yes — rigging weight is never included in the load calculation
- D. Yes — you can exceed capacity by 10% for a short-duration lift
Show Explanation
Explanation:
Rated capacity is the maximum total suspended load — including the weight of all rigging, slings, hooks, and the headache ball. Total here is 8,100 lbs, which exceeds the 8,000 lb chart limit. The lift cannot be made at this radius.
Question 2: A telescoping boom truck load chart has separate sections for "on outriggers fully extended" and "on outriggers retracted." You have deployed outriggers but only 75% extended. Which chart applies?
- A. The fully extended chart, because outriggers are deployed
- B. The on-tires chart, because outriggers are not fully extended(correct)
- C. You must interpolate between both charts
- D. Either chart may be used at operator discretion
Show Explanation
Explanation:
If outriggers are not in the exact configuration shown on the load chart, you must use the more conservative (lower capacity) chart. Partial extension does not achieve the stability of full extension, so the on-tires (retracted) chart applies.
Question 3: What is "two-blocking" on a telescoping boom truck?
- A. Using two outrigger pads stacked under one float
- B. The condition where the upper load block contacts the boom tip(correct)
- C. Lifting two separate loads simultaneously
- D. Deploying both front and rear outriggers at the same time
Show Explanation
Explanation:
Two-blocking occurs when the traveling block (headache ball or hook block) rises and contacts the boom tip block, which can snap the wire rope or cause structural failure. Anti-two-block devices are required by ASME B30.5 to stop hoist motion before contact.
Question 4: As you extend a telescoping boom to a longer length at the same angle, what happens to the rated capacity?
- A. It stays the same — angle is the only variable
- B. It increases — a longer boom can reach more load
- C. It decreases — longer boom means greater radius and less capacity(correct)
- D. It depends on the load chart manufacturer
Show Explanation
Explanation:
Extending the boom at a fixed angle increases the horizontal radius. Greater radius creates a larger overturning moment, which reduces the rated capacity shown in the load chart.
Question 5: What does the "over-end" section of a boom truck load chart describe?
- A. Lifts made at maximum boom extension
- B. Lifts made with the boom positioned over the front or rear of the truck(correct)
- C. Lifts that require special over-the-side outrigger pads
- D. Lifts exceeding the gross vehicle weight rating
Show Explanation
Explanation:
Boom trucks have higher capacity when lifting over the front or rear (the structural strong axis) versus over the side. The load chart is divided into over-end and over-side sections to reflect this. Always verify your boom orientation before selecting the applicable column.