NCCCO Mobile Crane Assembly and Disassembly 2 — Questions and Answers
Question 1: What is the first step that must be completed before beginning mobile crane assembly?
- Install the boom sections
- Conduct a site survey and ground bearing capacity assessment (Correct answer)
- Connect all hydraulic lines
- Attach the load hook
Correct answer: Conduct a site survey and ground bearing capacity assessment
A thorough site survey including ground bearing capacity assessment must be completed first to ensure the ground can support the crane and outrigger loads.
Ground conditions are the foundation of safe crane assembly. Inadequate ground bearing capacity has caused numerous crane collapses during setup. The site survey identifies soil type, underground utilities, slopes, and areas of fill or weak ground. Outrigger pad placement must be based on verified ground bearing capacity data from geotechnical assessment or site investigation before assembly begins.
Question 2: When erecting a lattice boom crane, in what sequence should boom sections typically be assembled?
- From tip section to butt section
- From butt section (base) upward toward the tip (Correct answer)
- In any order as long as all pins are secured
- Starting with the middle sections first
Correct answer: From butt section (base) upward toward the tip
Lattice boom assembly proceeds from the butt (base) section outward toward the tip, with each section connected and pinned before adding the next.
Assembling from butt to tip ensures each section is properly supported as it is added. Working outward from the base allows the assembled sections to be controlled and pinned securely before extending further. Reverse assembly (tip to butt) would leave unsupported sections hanging, creating uncontrolled load conditions and pin alignment difficulties that compromise assembly safety.
Question 3: What must be verified after installing counterweights during mobile crane assembly?
- That counterweights are painted the correct color
- That counterweight quantity and placement matches the load chart configuration being used (Correct answer)
- That counterweights are at least 10 feet from the ground
- That counterweights are installed before any boom sections
Correct answer: That counterweight quantity and placement matches the load chart configuration being used
Counterweight configuration must exactly match the load chart being used, as different lift configurations require specific counterweight amounts and positions.
Mobile crane load charts are developed for specific counterweight configurations. Using incorrect counterweight amounts or placement invalidates the load chart, either reducing actual capacity below what operators expect (creating overload risk) or creating asymmetric loading conditions that affect crane stability. After installation, the operator must verify counterweight weight and position against the applicable load chart configuration.
Question 4: Which component should be inspected specifically for proper engagement before the crane is put into service after assembly?
- The crane's paint condition
- All safety devices, limit switches, and anti-two-block systems (Correct answer)
- The operator cab lighting
- The fuel tank level indicator
Correct answer: All safety devices, limit switches, and anti-two-block systems
All safety devices including load moment indicators, anti-two-block systems, and limit switches must be tested and verified operational before placing the crane into service.
Safety devices are the last line of defense against structural overload and equipment damage. After assembly, each device must be function-tested: anti-two-block protection prevents wire rope and hook block damage, load moment indicators alert operators to overload conditions, and travel and boom limit switches prevent mechanical overtravel. OSHA 29 CFR 1926.1416 requires inspection of all safety devices before operations begin.
Question 5: What is the purpose of the boom backstop or boom stop device on a mobile crane?
- To prevent the boom from being lowered too far
- To prevent the boom from traveling past vertical and over-luffing backward (Correct answer)
- To lock the boom in the transport position
- To measure boom angle accurately
Correct answer: To prevent the boom from traveling past vertical and over-luffing backward
Boom backstops prevent the boom from exceeding maximum boom angle, which could cause it to tip backward (over-luffing), potentially causing catastrophic structural failure.
If a crane boom is raised beyond the maximum design angle, it can pass through vertical and fall backward, a catastrophic failure mode called over-luffing or boom back. Boom backstops are mechanical stops or hydraulic cylinders that prevent the boom from reaching this dangerous position. They must be properly adjusted and verified during assembly as a critical safety component of the crane configuration.
Question 6: During mobile crane disassembly, when should the wire rope be removed from the boom?
- Before any boom sections are disassembled
- After the boom is fully lowered and the last section is on the ground (Correct answer)
- As each boom section is removed from the assembly
- Wire rope removal is not part of the disassembly process
Correct answer: After the boom is fully lowered and the last section is on the ground
Wire rope should be removed after the boom is fully lowered to a safe position and controlled, preventing uncontrolled rope movement during structural disassembly.
Removing wire rope while the boom is still elevated creates uncontrolled load conditions and fall hazards. Once the boom is fully lowered to the ground or a stable near-ground position, the wire rope can be carefully removed from sheaves and drums following the manufacturer's procedure. Attempting to remove or reeve rope while working at height on an elevated boom adds unnecessary risk to an already complex operation.
NCCCO Mobile Crane Assembly and Disassembly 2
What is the first step that must be completed before beginning mobile crane assembly?