Load Charts 101 — Reading the Chart (and the Notes That Fail Operators)

Core · Domain 4: Load Charts & Capacity · ~25 min · cited to OSHA 1926 Subpart CC + ASME B30.5-2025 (Authored & cited — pending SME review.)

1. Why this matters

Load charts are roughly 26% of the CCO Core written exam — the single heaviest domain and the one most candidates fail on. Beyond the exam, the chart is the line between a routine pick and a tip-over or boom failure. Two things to anchor on:

• The chart is a legal limit. OSHA prohibits operating a crane in excess of its manufacturer rated capacity (29 CFR 1926.1417(b)–(c)). The chart isn't a suggestion or a "safe estimate with margin to spare" — it's the ceiling.
• Most chart errors aren't arithmetic — they're skipped notes. A candidate can read the grid perfectly and still get a deadly-wrong answer by ignoring a footnote. This lesson spends as much time on the notes as on the numbers.

2. What a load chart actually is (so the rules make sense)

Every capacity in the chart is the lesser of two independent limits at that exact configuration:

1. Structural strength — how much the boom, jib, cylinders, and components can physically carry before something yields or buckles. This dominates at short radii / steep boom angles, where the crane is nowhere near tipping but the steel is highly stressed.
2. Stability (tipping) — how much can be lifted before the crane starts to tip about its tipping fulcrum (the outrigger float centerline, or the tire/track contact line). Stability-based ratings are set as a percentage of the tipping load — by industry test code (SAE, referenced by ASME B30.5), typically 85% of tipping on outriggers and 75% on tires. Stability dominates at long radii.

The chart prints whichever number is smaller. That's why the bold "stability line" matters (Section 8): above it you're structure-limited; below it you're tip-limited. Understanding this tells you when counterweight helps and when it does nothing.

Cited: ASME B30.5-2025 §5-1.1 (Load Ratings & Technical Information), §5-1.2 (Backward Stability).

3. Key terms (get these exact)

• Operating (working) radius — horizontal distance from the center of rotation to the center of the hook/load line. Not boom length, not distance from the cab.
• Loaded radius — the radius with the load applied. The boom deflects and the machine settles under load, pushing the hook outward, so the loaded radius is larger than the radius you measured empty. Charts are read at the loaded radius.
• Boom length / boom angle — telescoping length and the angle of the base section above horizontal.
• Gross capacity — the raw number in the chart cell.
• Net (available) capacity — gross minus all load-handling devices (Section 5).
• Rated capacity — the maximum the manufacturer permits at a configuration = the charted value.
• Tipping fulcrum — the line the crane would rotate about if it tipped (outrigger float line / tire line). Radius and stability are referenced to it.
• Quadrant / area of operation — the zone the load is over (e.g., over-rear vs over-side vs over- front). Capacity can differ by quadrant; a 360° chart (like ours) gives one value for all directions, which is the most conservative case.
• Parts of line — the number of hoist-rope segments supporting the load block (Section 6).

4. Reading the chart — step by step (Academy generic telescopic chart)

1. Verify the setup matches the chart's stated configuration: outriggers fully extended, 360°, firm ground, level within 1%. If outriggers are partially extended or you're on rubber, this chart does not apply — you need the separate chart for that configuration.
2. Establish the loaded radius and boom length for the planned lift.
3. Read gross at that row/column. Example: 80 ft boom, 30 ft radius → 43,000 lb gross.
4. Subtract all deductions (Section 5) to get net. Hook block 1,000 + slings 500 → 41,500 lb.
5. Check the second limit — reeving (Section 6): is the rope/parts-of-line capacity ≥ what you're lifting? The lift is limited by the smaller of net chart capacity and reeving capacity.
6. Compare: (load + rigging) must be ≤ the governing limit. Then check the lift as a % of capacity — many crews set an internal caution threshold (e.g., re-plan above 75–90%).

5. Gross → net: deductions (where points and cranes are lost)

The chart capacity is for a bare hook line. Everything you hang to make the lift is part of the load and comes out of capacity:

Two of these are the classic exam traps because they apply even when you're not using them:

Erected-jib trap: 100 ft boom, 40 ft radius shows 27,000 lb. Load is 25,500 lb. An offsettable jib is erected but stowed (not used). Lookup says fine (25,500 < 27,000) — but the jib costs 2,000 lb → effective 25,000. 25,500 > 25,000 → NO LIFT. The note flips it.

Aux-sheave trap: 80 ft boom, 50 ft radius = 22,500 lb. Aux tip sheave installed + hook block reeved. Net for the load = 22,500 − 150 − 1,000 = 21,350 lb. Forgetting the small 150 is the trap.

Jib + reeved-block trap: lifting on the jib, you must also deduct main-boom devices left reeved (e.g., the hook block) from the jib capacity.

6. The second limit: wire rope & parts of line

Chart capacity assumes the load is actually reeved with enough parts of line. Each part of hoist rope shares the load, so the hook capacity from reeving = (rope's rated single-line pull) × (number of parts). If the charted capacity is higher than what your current reeving can carry, the reeving governs — you must add parts of line (or you simply cannot lift the charted number).

Example: a rope rated 12,000 lb/line, reeved with 4 parts → 48,000 lb hook capacity. If the chart says 60,000 lb at your config, you're rope-limited to 48,000 until you reeve more parts.

Always confirm the chart's wire-rope/parts-of-line reference, not just the capacity grid.

Cited: ASME B30.5-2025 §5-1.1, §5-1.7 (Ropes and Reeving Accessories).

7. Structural vs. stability — and when counterweight helps

• Above the bold line → structural limit. The number is set by the strength of the boom/components. Adding counterweight does nothing to raise it — counterweight fights tipping, not steel stress.
• Below the bold line → stability limit. Here the machine is tip-governed; correct counterweight, outrigger setup, and being level are what protect you.
• Practical takeaway: never reason "I'll throw on more counterweight to pick more" at a short-radius, structure-limited pick. It won't work and signals a dangerous misunderstanding.

Cited: ASME B30.5-2025 §5-1.1, §5-1.2.

8. The range diagram

A separate diagram pairs boom length + boom angle with the resulting radius and hook (tip) height. Use it to confirm a lift is geometrically reachable — can this boom, at a workable angle, get the hook to the needed radius and height? — before you trust the capacity cell. A lift can be within capacity yet unreachable, or reachable only at an angle that changes your radius.

9. Configuration factors that change everything

• Outrigger extension — fully vs. intermediate vs. retracted each has its own chart. Never apply a percentage in your head; use the matching chart. Partial extension is permitted only if the manufacturer provides charts for it.
• On rubber (on tires) — much lower capacities, separate chart, often with creep/pick-and-carry rules and speed limits.
• Pick-and-carry / traveling with a load — only if the manufacturer allows it, within stated boom position, capacity, ground, and speed limits.
• Quadrant — over-the-side is usually weakest; a 360° chart already assumes the worst direction.
• Wind & dynamics — charts assume freely suspended loads, no wind, smooth control. Wind on the load and the boom, swinging, and sudden stops all add effective load; reduce per the manufacturer and stop at the wind limit.
• Level — within 1%; out-of-level rapidly erodes capacity and is a common tip-over cause.

10. Putting it together — a worked lift

Plan: pick a 19,000 lb load at a 50 ft radius. Rigging: hook block 1,000 + slings 1,000 (total devices 2,000). No jib, no aux sheave. Outriggers full.

1. Total to lift = 19,000 + 2,000 = 21,000 lb must be ≤ net.
2. Pick a boom length that reaches 50 ft with margin. At 100 ft boom, 50 ft radius → 20,500 gross. Net = 20,500 − 2,000 = 18,500. 21,000 > 18,500 → won't work on the 100 ft boom.
3. Try 80 ft boom, 50 ft radius → 22,500 gross; net = 22,500 − 2,000 = 20,500. 21,000 > 20,500 → still short. Shorten radius or boom.
4. At 80 ft boom, 40 ft radius → 31,000 gross; net 29,000 → comfortably OK if the geometry lets you set up at 40 ft. Decision: reduce radius to 40 ft (reposition the crane) rather than force it.

That sequence — total load incl. devices, find net, check reeving, adjust radius/boom — is exactly the judgment the exam (and the job) wants.

11. Common mistakes

• Reading the unloaded radius instead of the loaded radius.
• Treating gross as net (forgetting hook block / ball / slings).
• Ignoring an erected-but-unused jib or an installed aux sheave.
• Using the fully-extended-outrigger chart while on partial outriggers or rubber.
• Assuming counterweight raises a structure-limited capacity.
• Forgetting the parts-of-line / rope limit can be lower than the chart.
• Not re-checking radius after the boom deflects under load.

12. Quick check

1. 60 ft boom, 25 ft radius (gross 61,000). Hook block 1,000 + slings 800. Max load? → 59,200 lb.
2. Jib erected but not used — does it affect main-boom capacity? → Yes, deduct it.
3. Chart shows 60,000; rope reeved 4 parts at 12,000/line. Governing limit? → 48,000 lb (reeving).
4. A pick is above the bold line. Will adding counterweight raise capacity? → No (structural limit).

13. Key terms glossary

Radius · Loaded radius · Boom length/angle · Gross/Net capacity · Rated capacity · Tipping fulcrum · Structural vs. stability limit · Quadrant/area of operation · Parts of line · Deduction · Range diagram — (definitions in Section 3 / inline).

14. The standards behind this

• OSHA 29 CFR 1926.1417(b)–(c) — do not operate above rated capacity.
• ASME B30.5-2025 §5-1.1 / §5-1.1.3 — load ratings, technical info, the load rating chart, deductions.
• ASME B30.5-2025 §5-1.2 — backward stability (the structural-vs-stability basis).
• ASME B30.5-2025 §5-1.7 — ropes & reeving accessories (parts of line).
• ASME B30.5-2025 §5-3.4.7 — footing / level within 1%.

15. Now test yourself

→ Practice: Load Charts & Capacity — lookups, net-capacity, the note-traps, jib charts, go/no-go, and max-radius questions built on this same chart.