LBT Load Charts — Lattice Boom, Truck-Mounted

Specialty: LBT (Lattice Boom — Truck) · Domain: Load Charts (~35% of the exam) · ~22 min · OSHA 1926 Subpart CC + ASME B30.5-2025 (Authored & cited — pending SME review. Capacities reference the synthetic Academy Generic Lattice Truck — 100-Ton chart; no OEM chart is reproduced.)

1. The LBT chart — assembled lattice boom on outriggers

Rated capacity = maximum allowable load at a given radius and configuration (ASME B30.5-2025 §5-1.1), read from a boom-length × loaded-radius grid. The difference from a telescopic crane: a lattice boom is a built-up structure assembled from sections to a fixed length on the ground (ASME B30.5-2025, GENERAL NOTE to Fig. 5-0.2.1-4) — you do not telescope it, you build it. Field: lattice truck, conventional truck crane, stick.

So the boom-length column is the length you assembled, and there is no "extend under load." The grid still prints the lesser of structure vs stability, stability rated as a percentage of tipping (§5-1.1.1(a); Table 5-1.1.1-1).

Test trap: expecting a telescoping/extend-under-load note on an LBT chart. There isn't one — the boom is a fixed assembled length. If you need a different length, you disassemble and rebuild, then read that column.

Recap: LBT boom is assembled to a fixed length; read that column; no telescoping, no extend-under-load.

2. Quadrant is king — over-rear vs over-side vs over-front

A truck crane on outriggers is not 360° equal. It is strongest over-rear, weaker over-side, and weakest over-front (over the cab/steer axles). Each area has its own chart. Field: over the back, over the side, over the front.

The Academy LBT chart is the over-rear chart; over-side and over-front capacities are lower and read from their own charts (chart Note 1). There is no single 360° number.

Test trap: reading the over-rear chart for a swing over the side. On a truck crane the side is the weak quadrant — using the over-rear number over the side is how you tip a "charted" pick.

Recap: pick the chart for the actual area of operation; over-rear ≠ over-side ≠ over-front, and side/front are lower.

3. Loaded radius, gross → net

Read the loaded radius (radius with the load applied — larger than the empty-hook radius from boom deflection; chart Note 4). The cell is gross; net = gross minus every device, since blocks, balls, and slings count as load (§5-1.1.1(c); chart Note 2):

Test trap: 90 ft boom, 30 ft radius, over-rear = 63,000 gross (Academy chart). Load 60,000, block 1,500, ball 400 → net 61,100. 60,000 ≤ 61,100 → OK. Swing the same pick over-side and the governing chart cell drops below 60,000 → NO LIFT. Same load, same geometry, different quadrant.

Recap: loaded radius, net = gross − block − ball − rigging − any erected jib, and re-check net in the quadrant you'll actually swing to.

4. On outriggers vs on rubber (pick-and-carry)

A truck crane has two families of chart: on outriggers (fully extended and set — 85% stability basis, Table 5-1.1.1-1) and on rubber / on tires (pick-and-carry). On rubber the capacities are far lower and carry creep-speed, tire-pressure, and boom-centered rules. Partial outrigger extension is permitted only with the manufacturer's matching chart at equal beam settings (§5-3.2.1.5(k)). Field: on the sticks, on rubber, pick-and-carry.

Test trap: using the on-outrigger chart while rolling with a load, or the fully-extended chart on partial beams. Each is a different chart — never interpolate between them.

Recap: on-outrigger and on-rubber are separate charts; equal beam settings for partials; no interpolation.

5. Reeving, two-block, assembled length

• 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; chart Note 7).
• Use the actual assembled boom length column; intermediate lengths use the next longer rated column (chart Note 6) — do not interpolate rows/columns beyond the table.

Recap: confirm parts-of-line ≥ load, ATB working, and read the actual/next-longer assembled length.

6. Worked go/no-go

Plan (Academy LBT chart, over-rear): 45,000 lb at 40 ft loaded radius, outriggers full. Block 1,500 + ball 400 + slings 1,100 = 3,000 devices.

1. Total = 45,000 + 3,000 = 48,000 lb ≤ net?
2. 90 ft boom, 40 ft radius, over-rear → 47,000 gross. Net = 44,000. 48,000 > 44,000 → NO LIFT.
3. 60 ft boom, 40 ft radius, over-rear → 58,000 gross. Net = 55,000 → OK if 60 ft clears the height and the pick stays over-rear.
4. Never exceed the cell (29 CFR 1926.1417(b)–(c)).

Recap: total with devices → net → shorter/assembled boom or better quadrant to clear it → never round up.

Common traps

• Using the over-rear chart for an over-side or over-front swing.
• Expecting an extend-under-load note (lattice boom is fixed length).
• Treating gross as net; missing block/ball/erected-jib deductions.
• Using the on-outrigger chart on rubber, or the full chart on partial beams.
• Interpolating beyond the table instead of using the next-longer column.

Quick check

1. Strongest quadrant for a truck crane on outriggers? → Over-rear. Weakest? → Over-front.
2. 120 ft boom, 50 ft loaded radius, over-rear = 28,000 gross; block 1,500 + ball 400. Net? → 26,100 lb.
3. Can you telescope an LBT boom under load? → No — it's an assembled lattice boom, fixed length.
4. Rolling a load on tires — which chart? → The on-rubber / pick-and-carry chart, not the outrigger chart.

Now test yourself

→ Practice: LBT — Load Charts — quadrant selection, net-capacity, on-outrigger vs on-rubber, and assembled-length reading on the Academy lattice-truck chart.