LBC Load Charts — Lattice Boom, Crawler

Specialty: LBC (Lattice Boom — Crawler) · 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 Crawler — 200-Ton chart; no OEM chart is reproduced.)

1. The LBC chart — assembled lattice boom, on tracks, no 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. A crawler is a rotating superstructure and lattice boom on crawler treads (§5-0.2.1) — it works on its tracks, without outriggers. The lattice boom is assembled to a fixed length on the ground (GENERAL NOTE to Fig. 5-0.2.1-4). Field: crawler, lattice crawler, on tracks.

Cell = lesser of structure vs stability, stability set as a percentage of tipping (§5-1.1.1(a); Table 5-1.1.1-1).

Recap: LBC = assembled lattice boom on tracks, no outriggers, fixed boom length; cell = lesser of structure vs stability.

2. The 75% rule — the number that separates crawlers

A crawler working on its tracks without outrigger support is rated at 75% of the tipping load (ASME B30.5-2025 Table 5-1.1.1-1). Only when a crawler has outriggers that are fully set do you move to the 85% chart. Field: on tracks, 75 percent chart.

Test trap: applying 85% to a crawler on tracks. On rubber-or-tracks without outriggers, the stability basis is 75%, not 85%. The Academy LBC chart (Note 2) is a 75% on-tracks chart; grabbing an 85% number is a 13% overload waiting to tip.

Recap: on tracks, no outriggers = 75% of tipping; 85% only applies with outriggers fully set.

3. Area of operation — over-side vs over-end

A crawler rotates 360°, but capacity is not equal in all directions. The narrow dimension (over-side) is the least stable and gives the lowest capacity; over-end (over an idler/drive end, the long dimension) rates higher and uses a separate chart. Field: over the side, over the end.

A 360° chart prints the over-side (conservative) value so it is safe in any direction — but if the manufacturer supplies an over-end chart and you stay over the end, you may use its higher values (chart Note 1).

Test trap: using the higher over-end numbers while swinging across the side. The moment the load passes over the side, the over-side (lower) chart governs. A 360° pick must respect the over-side value through the whole swing.

Recap: over-side is weakest and governs any 360° swing; over-end is a higher, separate chart valid only while you stay over the end.

4. 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). Cell is gross; net = gross minus every device, since blocks, balls, and slings count as load (§5-1.1.1(c); chart Note 3):

Test trap: 160 ft boom, 40 ft loaded radius, over-side = 77,000 gross (Academy chart). Load 73,000, block 2,000, ball 500 → net 74,500. 73,000 ≤ 74,500 → OK. Forget the 2,500 lb of devices and you read 77,000 as usable — a false go.

Recap: loaded radius, net = gross − block − ball − rigging − any erected jib.

5. Traveling with a suspended load

Crawlers can travel with a suspended load — but only under the manufacturer's stated conditions for that machine (boom position, radius, ground, speed) (chart Note 7; ASME B30.5-2025 §5-3.4.5). Field: walking the load, crawling with the load.

Test trap: assuming any crawler may freely pick-and-carry. It is permitted only within the manufacturer's rules; outside them it is prohibited, and firm, level, planned ground still governs.

Recap: travel with a load only within the manufacturer's stated conditions — not a free capability.

6. 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).
• Use the actual assembled boom length column; between entries, use the next longer column (chart Note 6) — never interpolate beyond the table.

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

7. Worked go/no-go

Plan (Academy LBC chart, 360° swing so over-side governs): 60,000 lb at 50 ft loaded radius, on tracks. Block 2,000 + ball 500 + slings 1,500 = 4,000 devices.

1. Total = 60,000 + 4,000 = 64,000 lb ≤ net?
2. 120 ft boom, 50 ft radius, over-side → 70,000 gross. Net = 66,000. 64,000 ≤ 66,000 → OK (thin).
3. 160 ft boom, 50 ft radius → 59,000 gross. Net = 55,000 → NO LIFT at that length. Shorter assembled boom rates higher at this radius.
4. Never exceed the cell (29 CFR 1926.1417(b)–(c)).

Recap: total with devices → net at the over-side value → choose the assembled length that clears it → never round up.

Common traps

• Applying 85% to a crawler on tracks (it's 75%).
• Using over-end numbers while swinging over the side.
• Treating gross as net; missing block/ball/erected-jib deductions.
• Assuming free pick-and-carry instead of the manufacturer's stated conditions.
• Interpolating beyond the table instead of using the next-longer column.

Quick check

1. Crawler on tracks, no outriggers — stability basis? → 75% of tipping (Table 5-1.1.1-1).
2. Weakest area of operation on a crawler? → Over-side.
3. 200 ft boom, 60 ft loaded radius, over-side = 38,000 gross; block 2,000 + ball 500. Net? → 35,500 lb.
4. May a crawler travel with a suspended load? → Only under the manufacturer's stated conditions (§5-3.4.5).

Now test yourself

→ Practice: LBC — Load Charts — the 75% on-tracks basis, over-side vs over-end, net-capacity, travel-with-load rules, and assembled-length reading on the Academy lattice-crawler chart.