Work took place at the Puget Sound Naval Shipyard just outside Seattle, in nearby Bremerton, and lasted just over a month. Ness’s directive for the 550 USt (450t) GMK7550 was to replace the ship’s main mast, as the additional weight of new antennae exceeded the structural limit for the old mast. The heaviest load to be lifted onto the ship, however, was the GMK7550 itself. Weighing 450t (550 USt), it is the largest mobile crane in the Grove line, and had to be carried on board by an adjacent harbour crane.
Kurt Kleppe, vice president of Ness Cranes, said: “Lifting the crane onboard the ship was the most complicated part of the whole project, but having the GMK7550 on board the ship was crucial; we needed its excellent lifting capacity to take down the old mast and erect the new one.”
The first lift on board was to remove the original mast which weighed around 26,500kg (71,000lbs), and measured 32m (105ft) tall. With a 60m (197ft) maximum boom, the GMK7550 was able to reach the necessary heights for dismantling the old mast. With this completed, the crane installed the new mast which weighed almost twice as much as the original at 46,655kg (125,000lbs). Standing at a height of 35m (116ft) tall, USS Stennis’s new mast is more than capable of handling the necessary antennae inputs and alterations.
Ness started business in 1950 and today employs 57 people and owns 37 cranes; including 24 Manitowoc Crane Group products – 17 Grove mobile cranes and seven National boom trucks.
