NCCCO Lattice Boom Crane Configuration and Operations — Questions and Answers
Question 1: What is the primary function of a boom pendant (back hitch) on a lattice boom crane?
- It connects the load block to the hook at the boom tip
- It suspends and supports the boom from the mast or A-frame, controlling boom angle (Correct answer)
- It secures adjacent boom sections together during assembly
- It provides a secondary load path if the main hoist rope fails
Correct answer: It suspends and supports the boom from the mast or A-frame, controlling boom angle
Boom pendants run from the boom tip back to the crane's A-frame or mast, supporting the boom's weight and maintaining its working angle. They are part of the boom suspension system and must be correctly rigged and tensioned before any lifting begins.
Question 2: What distinguishes a luffing jib from a fixed jib on a lattice boom crane?
- A luffing jib uses wire rope construction while a fixed jib uses tubular steel
- A luffing jib can be raised or lowered independently while the crane is in service (Correct answer)
- A luffing jib is rated for heavier loads than a fixed jib of the same length
- A luffing jib requires a separate operator to control while the main operator handles the crane
Correct answer: A luffing jib can be raised or lowered independently while the crane is in service
A luffing jib can be raised and lowered (luffed) independently while the crane is working, allowing the operator to change working radius without repositioning the crane. A fixed jib is set at a fixed offset angle and cannot be adjusted during operations.
Question 3: When assembling boom sections on a lattice boom crane, what must be verified before adding additional sections?
- All section pins are fully inserted and secured with their retaining devices (Correct answer)
- The load block has been reeved through each section before pinning
- The counterweight has been fully installed to match the additional boom weight
- The hydraulic outriggers have extended to maximum spread
Correct answer: All section pins are fully inserted and secured with their retaining devices
Each boom section must be connected using the correct pins, with all retaining devices (cotter pins, keeper plates, or snap rings) fully installed before the next section is added or the boom is raised. A missing or partially inserted pin can cause catastrophic boom collapse.
Question 4: What is the primary ground-bearing advantage of a crawler crane over a rubber-tired mobile crane?
- Crawlers allow higher travel speeds on paved surfaces
- Crawlers distribute the crane's weight over a much larger footprint, reducing ground bearing pressure (Correct answer)
- Crawlers eliminate the need for outriggers during lifting operations
- Crawlers allow the crane to travel on public roads without oversize permits
Correct answer: Crawlers distribute the crane's weight over a much larger footprint, reducing ground bearing pressure
Crawler undercarriages spread the crane's total weight across the full length of both crawler pads, dramatically reducing ground bearing pressure per square foot compared to rubber-tired cranes that concentrate weight on discrete tire contact patches. This makes crawler cranes better suited for soft or uneven terrain.
Question 5: What hazard results from allowing boom suspension pendants to go slack on a lattice boom crane while a load is being handled?
- Slack pendants cause the hoist rope to jump off the boom tip sheave
- Slack pendants allow the boom to swing laterally beyond the rated radius
- Slack pendants remove the boom's rear support, allowing the boom to kick forward suddenly when load is applied, increasing radius uncontrollably (Correct answer)
- Slack pendants increase wind-induced vibration that fatigues the lattice sections
Correct answer: Slack pendants remove the boom's rear support, allowing the boom to kick forward suddenly when load is applied, increasing radius uncontrollably
If boom pendants go slack, the boom loses its rear suspension. When a load is applied, the boom can rotate forward suddenly (boom fallover), dramatically increasing the working radius beyond the load chart value — frequently causing the crane to tip or the boom to buckle.
Question 6: A 'superlift' configuration on a large lattice boom crane is designed to accomplish what?
- Reduce the crane's overall height to allow operation under power lines
- Add counterweight on a trailing arm to allow heavier lifts at greater radii (Correct answer)
- Raise the crane's center of gravity to permit steeper boom elevation angles
- Transfer load directly to the crawlers rather than through the swing bearing
Correct answer: Add counterweight on a trailing arm to allow heavier lifts at greater radii
A superlift system positions additional counterweight on an extended rear frame or trailing arm, increasing the effective counterbalancing moment. This allows the crane to safely lift heavier loads at longer radii than possible with standard counterweight configurations mounted at the crane body.
NCCCO Lattice Boom Crane Configuration and Operations
What is the primary function of a boom pendant (back hitch) on a lattice boom crane?