Tall order for Essex
20 June 2011
A barge-mounted Manitowoc 888 Ringer crawler crane, belonging to Essex Crane Rental Corp., helped replace a navigational lock gate at the John Day Dam on the Columbia River, USA.
Situated between Oregon and Washington, the downstream navigational lock gate is 113 feet (37 m) tall, making it the tallest lock in the United States. Advanced American Construction, Inc., the contractor for the project, chose the Manitowoc 888 Ringer, mounted on a barge, to reduce the load radius that would otherwise be required when lifting on land.
The 1,000 US ton gate was removed and replaced in four sections, weighing up to 572,400 pounds (260 tonnes). Two of the components, weighing 130,000 pounds (59 tonnes) each, were lifted from the roof of the lock towers, more than 130 feet (43 m) above the barge.
The inherent instability of working on a barge also presented challenges, said Manitowoc. The contractor used a self-contained ballast system to transfer water between hull tanks to steady the barge as the crane hoisted each load. Maintaining balance was critical because, for the crane to complete the picks, the bow of the barge needed to be secured within six inches of the dam.
The Manitowoc 888 Ringer has a capacity of 661 US tonnes and a maximum jib capacity of 275 US tonnes. It has a 435 foot (133 m) maximum radius and a 45 foot (13.7 m) diameter ring. For this project, the crane was rigged with 250 foot (76 m) of boom and 1.4 million pounds (635 tonnes) of counterweight.
The work on the John Day Dam is part of a larger maintenance and repair initiative including the John Day, Dalles, and Lower Monumental dams along the Columbia-Snake Rivers. The project, which includes replacement of the gates, drive machinery, and electrical systems, began in October 2010 and was complete in March 2011.
