SP load cells assist ship-to-shore crane project

Lifting Gear Hire (LGH) provided 16 wireless compression load cells from Straightpoint to perform benchmark weighing as 10 ship-to-shore cranes were raised 33 feet by Shanghai Zhenhua Port Machinery Company (ZPMC) at Port of Los Angeles in early August.

The 150-metric ton capacity load cells combined to weigh one Noell ship-to-shore container handling crane, originally estimated to have a weight of 1,350te, and provide benchmark data before it and nine other cranes were to be raised to accommodate larger ships calling the port.

The project, managed by ZPMC North America, involved raising the cranes and inserting longer leg sections; it was a collaborative effort between the crane’s original equipment manufacturer (OEM) and ZPMC. Structural fabrication of the new leg sections and frame bracing was accomplished at ZPMC’s Shanghai facility.

Rick Pope, vice president at ZPMC North America, explained that a key part of the project included benchmark weighing of one raised crane to determine the new, as-built weight and center of gravity. He said, ”From this data, the crane OEM calculated the required concrete ballast that needed to be added to establish the crane’s designed operational center of gravity and stability. The results became the basis of ballasting for the other cranes being raised.”

The weighing procedure included lifting the crane utilizing ZPMC’s self-propelled modular trailers, placing the load cells in pairs under the eight intermediate gantry equalizers on specially designed pedestals, and lowering the crane down to rest on the load cells. The crane was lifted off the load cells between trials to allow for three distinct weighing evolutions.

The initial as-built weight of the crane as provided in historical documents was 1,185te. Post-construction weighing indicated the raising added 193te, for a total pre-ballast weight of 1,378te. Concrete ballast was added according to OEM specifications and resulted in a post-ballast weight of 1,414te and shift of the operational center of gravity approximately 3 feet toward the rear of the crane.

LGH also provided a rugged SP wireless tablet with data logging software and USB wireless base station. The data logging software provided user-configurable screens, recording the physical location of the load cells and collection of data. Center of gravity software collected data over three trials of weighing to calculate an average. A report was automatically created upon completion of the tests, including each load cell’s load, location, calculated center of gravity and standard deviation of weight data.

John Molidor, director of projects and market development at Straightpoint, said, “It was great to witness the application in person and get a first-hand impression of the 16 load cell system delivering safety and accuracy to such a landmark project. We enjoyed working with LGH and ZPMC North America to deliver the state-of-the-art solution.”