TSS Load Charts — Telescopic Boom, Fixed Cab

Specialty: TSS (Telescopic — Fixed Cab) · Domain: Load Charts (~35% of the exam) · ~22 min · OSHA 1926 Subpart CC + ASME B30.5-2025 (Authored & cited — pending SME review. Capacities below reference the synthetic Academy Generic Telescopic — 90-Ton chart; no OEM chart is reproduced.)

1. What a TSS chart is — a hydraulic telescopic chart

Rated capacity is the maximum allowable load at a given radius and configuration (ASME B30.5-2025 §5-1.1). On a telescopic crane it is set by a grid indexed by boom length and loaded radius, printed for one exact setup: outriggers fully extended and set, firm level ground, 360°. Field: the chart, the load chart, cap chart.

Every cell is the lesser of two limits — structural strength (short radius, steep boom) or stability (long radius), the latter rated as a percentage of tipping (§5-1.1.1(a); Table 5-1.1.1-1). The chart prints the smaller.

Test trap: treating the chart as one number for the whole machine. It is per boom-length and per radius and per outrigger/quadrant configuration. Change any one and you read a different cell — or a different chart.

Recap: TSS chart = boom-length × loaded-radius grid, one configuration, cell = lesser of structure vs stability.

2. The fixed-cab wrinkle

TSS = telescopic boom, fixed cab — the operator cab is mounted to the carrier and does not rotate with the boom (ASME B30.5-2025 §5-0.2.1, single control station). Field: fixed cab, carrier-cab crane, taxi-cab.

This changes nothing about how you read the capacity grid, but it changes your quadrant awareness: because the cab faces forward while the boom swings, you must track which area of operation the load is over from the chart, not from what you see out the window.

Test trap: assuming the cab direction tells you the working quadrant. It doesn't — the boom swings independently of the fixed cab. Confirm over-rear / over-side / over-front against the chart's stated area.

Recap: fixed cab = cab doesn't swing with the boom; read the quadrant off the chart, not the windshield.

3. Loaded radius — the number everyone reads wrong

Operating radius is the horizontal distance from the center of rotation to the center of the load (§5-1.1). Loaded radius is that distance with the load applied — boom deflection and machine settle push the hook outward, so it is always larger than the empty-hook radius. Field: working radius.

You read the chart at the loaded radius.

Test trap: measuring radius empty, then reading the chart. On the Academy tele chart, 100 ft boom at 50 ft = 20,500 lb, but at 60 ft = 14,000 lb. A load that deflects the boom out from 50 to ~55 ft has quietly dropped you toward the next-lower row.

Recap: always read the loaded (larger) radius, never the unloaded one.

4. Gross → net: deduct everything you hang

The chart cell is gross — bare hook line. Net (available) capacity is gross minus every load-handling device, because blocks, balls, and slings count as part of the load (§5-1.1.1(c)).

The last two are the classic traps: they cost capacity even when stowed.

Test trap: 80 ft boom, 40 ft radius = 31,000 lb gross (Academy chart). Load 29,500 lb, hook block 1,000, and an offsettable jib erected-but-stowed costs 2,000. Net = 31,000 − 1,000 − 2,000 = 28,000. 29,500 > 28,000 → NO LIFT, even though the grid cell looked fine.

Recap: net = gross − (block + ball + rigging + any erected jib/aux sheave). An erected jib is a deduction whether you use it or not.

5. Extending the boom under load

Telescopic sections may be extended or retracted under load only within the manufacturer's stated maximum for that motion — the chart states the maximum loads permitted during actual boom extension/retraction (ASME B30.5-2025 §5-1.1.3(b)(10)). Field: tele under load, powering out.

Moving sections under load adds dynamic and hydraulic demand a static cell does not cover, so the permitted load during motion is typically lower than the static rating at the same geometry.

Test trap: "lighter loads extend faster" or "OSHA sets a fixed 50% reduction." Neither is true — the chart's own note governs the max during extension, and it applies to telescopic booms specifically.

Recap: extend/retract under load only per the chart's boom-motion note, not the static cell.

6. Outrigger position and quadrant — match the chart, don't interpolate

Each outrigger position is its own chart. Fully extended, intermediate, and retracted each rate differently, and partial extension is permitted only when the manufacturer supplies that chart and the beams are set at equal positions matching that chart (ASME B30.5-2025 §5-3.2.1.5(k)). Field: on full, mid, on rubber.

• On outriggers, fully set: 85% stability basis (Table 5-1.1.1-1).
• On rubber / on tires: a separate, much lower chart, often with pick-and-carry (creep) rules.
• Quadrant: over-the-side is weakest; a 360° chart already assumes the worst direction.

Read the boom-length indicator for actual length (§5-1.9.1(e)) and use the row for the actual length — not the base length, not the longest available.

Test trap: using the fully-extended chart with beams set to mid, or interpolating between two outrigger charts. There is no interpolation between configurations — wrong chart, wrong number.

Recap: one chart per outrigger position and quadrant; equal beam settings; actual boom length; never interpolate across configurations.

7. The second limit — reeving

Charted capacity assumes the reeving can carry it. Reeving capacity = single-line pull × parts of line; if the cell exceeds it, reeving governs (§5-1.7). An anti-two-block device must be operational before lifting (§5-1.9.10.1).

Example: rope 12,000 lb/line × 3 parts = 36,000 lb at the hook. Chart shows 43,000 → you are rope-limited to 36,000 until you add parts.

Recap: confirm parts-of-line capacity ≥ the load; the grid is not the only ceiling.

8. Worked go/no-go

Plan (Academy tele chart): pick 24,000 lb at 40 ft loaded radius, outriggers full, over-side. Rigging: block 1,000 + slings 800 = 1,800 lb devices. No jib.

1. Total to lift = 24,000 + 1,800 = 25,800 lb must be ≤ net.
2. 100 ft boom, 40 ft radius → 27,000 gross. Net = 27,000 − 1,800 = 25,200. 25,800 > 25,200 → short.
3. 80 ft boom, 40 ft radius → 31,000 gross. Net = 29,200. 25,800 ≤ 29,200 → OK if 80 ft reaches the height.
4. Never exceed the cell — OSHA prohibits operating above rated capacity (29 CFR 1926.1417(b)–(c)).

Recap: total the load with devices → net → pick the boom length that clears it → never round up.

Common traps

• Reading the unloaded radius instead of the loaded radius.
• Treating gross as net; missing an erected-but-unused jib or installed aux sheave.
• Using the fully-extended chart on partial outriggers or on rubber.
• Interpolating between outrigger/quadrant charts.
• Extending under load past the chart's boom-motion note.
• Assuming the cab direction is the working quadrant.

Quick check

1. 100 ft boom, 50 ft loaded radius, gross 20,500; block 1,000 + slings 500. Net? → 19,000 lb.
2. Offsettable jib erected but stowed — does it reduce main-boom capacity? → Yes, deduct it (§5-1.1.1(e)).
3. Beams set to mid-extension. May you use the fully-extended chart? → No — use the matching partial chart (§5-3.2.1.5(k)).
4. What governs the maximum load while powering the boom out? → The chart's boom-extension note (§5-1.1.3(b)(10)).

Now test yourself

→ Practice: TSS — Load Charts — net-capacity, note-traps, loaded-radius, outrigger/quadrant selection, and extend-under-load reading on the Academy telescopic chart.