Crawler cranes (or "lattice boom” crawlers) are usually the most eye-catching equipment on a job site. Their height and size let them handle loads that other cranes cannot support. With a reach up to 700 feet, they can pick up loads up to 2,000 tons.
The jib (the lattice structure used to extend the boom past the main boom) is most often a fixed jib, meaning it has a set angle relative to the boom and is stowed alongside the main boom. Sometimes the jib can fold into itself (known as a bi-fold jib), which allows a long jib to be stowed with a smaller footprint. Most manufacturers offer multi-functional jib systems that increase maneuverability and reach.
A luffing jib allows the jib angle to be changed ("luffed”) depending on where the load needs to be. The luffing jib is operated by a pulley or winch and works separately from the main boom.
The crane operator can also change the angle of the jib with a hydraulically offset jib, which uses a hydraulic cylinder instead of pulleys and a winch. These jibs are commonly found on hydraulic cranes.
Lattice boom/jib repair
Replacing a lattice or hydraulic crane boom or jib section is expensive and time-consuming. It could take weeks for a manufacturer to supply a new one, meaning your job is on hold until it arrives.
So here’s the good news: Damaged lattice booms don’t always have to be replaced. Booms get banged up in everyday operation. In the case of these small dents and scrapes, lacing repair may be all that is needed.
Boom repair is a specialized service that must be compliant with all applicable standards, such as OSHA, Cal-OSHA, ANSI and AWS. Technicians should refer to the manufacturer’s specifications to make sure they are using the correct materials. This may mean conducting metallurgical tests to determine steel quality, for example. The piece to be repaired has to be engineered, welded to precise specifications, non-destructive tested and certified.
OSHA mandates that all repair/adjusted equipment be inspected "by a qualified person after such a repair or adjustment has been completed, prior to the initial use.” This final inspection includes functional testing of the repaired parts and other components that might be affected by the repair. A simple load test should then be conducted by a qualified person will finalize the process.
Some crane manufacturers won’t approve repairs to chords. If the chords are damaged, replacing the damaged section of the boom may be your only option. OEM’s may also specify the number of lattices that can be repaired or replaced per boom over the section’s lifetime. They will also have guidelines (specific to the crane’s model) regarding how significant the damage can be and still be repaired without having to replace the boom outright.
Liability is a huge issue with cranes. A lot of crane dealers, rental companies and fleet owners do not want the manufacturer to know about repairs they’ve made for fear of getting a "flag” on their equipment. Third-party repairs (those not made by the manufacturer) increase potential liability for these folks—that’s why it is so important to use technicians with the expertise to provide the highest quality repair and rebuild services.