NCCCO Crane Type Identification and Applications 2 — Questions and Answers
Question 1: What is the primary advantage of an all-terrain crane over a rough terrain crane?
- All-terrain cranes have higher capacity than rough terrain cranes at all radii
- All-terrain cranes are designed for both highway travel at highway speeds and off-road operation, while rough terrain cranes require transport by trailer for road travel (Correct answer)
- All-terrain cranes are always less expensive to operate
- All-terrain cranes do not require outriggers for lifting
Correct answer: All-terrain cranes are designed for both highway travel at highway speeds and off-road operation, while rough terrain cranes require transport by trailer for road travel
All-terrain cranes can travel on public highways under their own power at highway speeds and also operate on rough job sites, whereas rough terrain cranes cannot travel on public roads at speed and require transport by trailer.
All-terrain (AT) cranes combine highway capability with the off-road mobility of rough terrain cranes. AT cranes have multi-axle all-wheel-drive and all-wheel-steering undercarriages that allow them to travel at highway speeds (60-plus mph) between sites, yet negotiate unpaved, muddy, or rough terrain on the job site. Rough terrain (RT) cranes have large, dedicated off-road tires and are highly maneuverable on job sites but typically cannot self-propel on public roads at highway speeds. All-terrain cranes tend to have higher capacities and longer boom lengths than rough terrain cranes. For urban construction projects where the crane must travel from site to site, AT cranes are a common choice.
Question 2: A crawler crane is selected for a long-duration heavy industrial lift. What is the main advantage of a crawler crane in this application?
- Crawler cranes can travel on public roads without permits
- Crawlers provide a very stable platform with high lifting capacity and can travel slowly with a suspended load over prepared surfaces (Correct answer)
- Crawler cranes require no ground bearing considerations
- Crawler cranes are the fastest type of crane to set up
Correct answer: Crawlers provide a very stable platform with high lifting capacity and can travel slowly with a suspended load over prepared surfaces
Crawler cranes offer exceptional stability due to their wide track base, can achieve very high lifting capacities, and can travel short distances on site with a suspended load — advantages that make them ideal for long-duration, heavy industrial projects.
Crawler cranes use steel tracks instead of wheels, providing a wide, stable base that distributes machine weight over a large ground area. Key advantages for heavy industrial applications include: very high rated capacities (some exceeding 3,000 tons), wide track base providing excellent stability without outriggers, ability to travel slowly with loads on prepared surfaces, less ground bearing pressure per unit area than wheeled machines of similar weight, and counterweights that can be expanded for maximum capacity. Disadvantages include inability to travel on public roads (must be disassembled and transported by specialized trailers) and potential for track damage to paved surfaces. Crawler cranes are the crane of choice for large-scale construction: refineries, power plants, bridge construction, and offshore module setting.
Question 3: A boom truck (service truck crane) is most appropriate for which type of work?
- Large heavy lifts over 50 tons requiring maximum reach
- Service and maintenance work requiring moderate lifts and utility of the truck body for material transport (Correct answer)
- High-rise building construction where the crane must climb with the building
- Lifts in restricted areas where outriggers cannot be deployed
Correct answer: Service and maintenance work requiring moderate lifts and utility of the truck body for material transport
Boom trucks combine a crane with a service body on a standard truck chassis, making them ideal for service, utility, maintenance, and delivery work requiring moderate lifts alongside the carrying capacity of the truck.
A boom truck (also called a service truck crane or knuckle boom truck) mounts a telescoping crane on a standard truck chassis, often combined with a service body, flatbed, or utility body. They are purpose-built for: utility and telecommunications work such as setting poles, stringing wire, and servicing equipment; HVAC and mechanical contractors for setting rooftop units and handling ductwork; tower maintenance and equipment installation; and general service and maintenance where the truck also carries the tools and materials needed for the job. Capacities typically range from 3 to 30 tons. NCCCO offers a specific Service Truck Crane certification (STC) for operators working with this equipment type, recognizing its unique operational characteristics.
Question 4: What distinguishes a tower crane from a mobile crane in terms of how it achieves its lifting radius?
- Tower cranes use a telescoping boom while mobile cranes use a fixed jib
- Tower cranes use a rotating horizontal jib with a trolley that travels in and out to change radius, while mobile cranes use an inclined boom that is raised or lowered to change radius (Correct answer)
- Tower cranes can only lift directly overhead; mobile cranes can reach outward
- Tower cranes have no rated capacity limits; mobile cranes are limited by their outrigger spread
Correct answer: Tower cranes use a rotating horizontal jib with a trolley that travels in and out to change radius, while mobile cranes use an inclined boom that is raised or lowered to change radius
Tower cranes use a horizontal jib with a trolley that travels in and out to change the working radius, while mobile cranes change radius by raising or lowering the inclined boom angle. This fundamental difference affects how each type is set up and operated.
Tower cranes have a vertical mast supporting a horizontal jib. A trolley travels along the jib's length to change the working radius (the distance from the mast centerline to the load). Radius is changed by moving the trolley — the jib stays horizontal. Mobile cranes have an inclined boom that pivots from a near-vertical angle (short radius, maximum capacity) to a more horizontal position (long radius, lower capacity). The boom angle is changed by luffing (raising or lowering the boom). This difference makes tower crane load charts fundamentally different from mobile crane charts — tower charts show capacity vs. radius while mobile crane charts relate capacity to boom angle, boom length, and radius.
Question 5: What is the primary difference in how an overhead bridge crane (EOT crane) achieves load movement compared to a mobile crane?
- Overhead cranes use an outrigger system for stability
- Overhead cranes travel on fixed runway rails mounted to the building structure, providing longitudinal, transverse, and vertical movement within a defined work envelope (Correct answer)
- Overhead cranes require a boom angle indicator for operation
- Overhead cranes can only lift loads up to 5 tons
Correct answer: Overhead cranes travel on fixed runway rails mounted to the building structure, providing longitudinal, transverse, and vertical movement within a defined work envelope
Overhead bridge cranes travel on fixed runway rails installed in the building, with the bridge spanning the runway width and a hoist trolley traveling along the bridge, providing 3-axis movement within the building's work envelope.
An overhead bridge crane consists of: end trucks that ride on runway rails mounted to the building columns or walls at high level, a bridge girder spanning between the end trucks, and a hoist trolley that travels along the bridge. Load movement is achieved in three axes: longitudinal (the bridge travels the length of the runway), transverse (the trolley travels across the bridge width), and vertical (the hoist raises and lowers the load). The crane's work envelope is the rectangular volume covered by the runway length, bridge span, and hook height. Overhead cranes are governed by ASME B30.2 and are the primary material handling solution in manufacturing, steel mills, power plants, and large maintenance facilities.
Question 6: Which crane type uses a lattice boom structure rather than a telescoping hydraulic boom, and what is the primary reason for choosing lattice construction?
- Lattice boom cranes include all hydraulic telescoping cranes for rough terrain use
- Lattice boom cranes (crawler, lattice boom truck, luffing tower) use truss structure because lattice provides the highest strength-to-weight ratio for very long boom lengths and maximum capacities (Correct answer)
- Lattice booms are only used on cranes below 10 tons capacity
- Telescoping booms are always stronger than lattice booms of the same length
Correct answer: Lattice boom cranes (crawler, lattice boom truck, luffing tower) use truss structure because lattice provides the highest strength-to-weight ratio for very long boom lengths and maximum capacities
Lattice boom construction uses a truss structure with open-web sections that provides maximum structural efficiency (strength-to-weight ratio) for very long booms. This allows much greater lengths and capacities than hydraulic telescoping booms.
Lattice boom cranes use a structural truss design where the boom is assembled from sections of welded steel forming an open-web lattice similar to a bridge truss. This construction provides: exceptionally high strength-to-weight ratio (the lattice removes material from the interior of the boom where stress is low, concentrating material at the outer chords where bending stress is highest), ability to achieve extremely long boom lengths (200 feet and beyond, plus jibs), and much higher lifting capacities at long radii compared to hydraulic cranes of similar weight. For heavy industrial and civil construction requiring capacities over 200 tons or boom lengths over 200 feet, lattice boom cranes (crawler or lattice boom truck) are the standard choice.
NCCCO Crane Type Identification and Applications 2
What is the primary advantage of an all-terrain crane over a rough terrain crane?