Underwater Propeller Change,
USS Enterprise, CVN-65

US Navy Divers Remove the Propeller

After the boss nut was broken off, the shaft threads were checked and chased. All appeared to be in perfect condition. The threads were cleaned and wrapped with a 9 thread line. The entire shaft was then covered with canvas and a thin protective sleeve. A large diameter wire rope grommets and 2-1/2 inch shackles were attached in each of the propeller lifting shell fittings. A snatch block and a tight grip wire were attached to the after fitting in preparation for rigging the 50 ton chain hoists. Propeller removing studs were machined down 0.040 of an inch and installed. (This allowed water to flow out of the huge threads without building up what we called Hydraulic Lock. Seawater doesn't compress, and if you don't give the water some place to go, it builds up enough pressure to prevent screwing bolts into their threaded holes.)

Two 50-ton chain hoist were placed on board the barge by the pier crane. The barge was then repositioned alongside Enterprise in line with frame to 228, where a tight grip wire was attached to the Enterprise after hull fitting. One snatch block was attached at the Enterprise after hull fitting and two additional snatch blocks were attached on the barge deck. Line's rigged through the snatch blocks were controlled by grip hoiss located on the barge. The 50-ton chain hoist was then hooked on to the tight grip wire which would support its way and guide its movement. Once in the vicinity of the after hull fitting it was disconnected from the tight grip wire and lowered so it could be attached to the grommet and shackle which was already on the after all fitting. The procedure was repeated to locate the other 50-ton chain hoist temporarily on the after all fitting. The shaft was then jacked over to position the propeller studs at 3 and 9 o'clock.

The pilgrim nut method was chosen for unseating the propeller after learning from NAVSEA that an excess of 700 tons of force would be required to unseat the propeller from the shaft. Preparations were made to install the pilgrim nut on the shaft and the backing played on the propeller stunts as soon as the backing plate had arrived from Puget Sound naval shipyard. The pilgrim nut was tested pier side using a 10 ton concrete block. The barge was then positioned alongside the carrier and the pilgrim nut was yard and stayed into position on the propeller shaft. The backing plate followed into its position on the propeller studs. The stud nuts were installed on the propeller studs, the pilgrim nut was tightened, and 4 by 6 inch wooden blocks were placed at 3 and 9 o'clock positions to absorb some of the impact when the propeller was unseated. 10,000 PSI of pressure was applied to the pilgrim nut to break the propeller free from the shaft taper. The propeller moved one inch along the shaft in two extensions of the pilgrim nut. The studs, nuts, backing plate and pilgrim nut were then removed.

The damaged Enterprise propeller was removed by the yard and stayed method from the forward to after air hoist. Once off the shaft, the propeller was positioned alongside the barge. It was suspended on the 50-ton air hoist which had been connected to the propeller balance beam. The barge was warped to within reach of the YD 116 floating crane, which hooked on to the propeller, lifted it from the barge balance laid it down on the pier. The propeller studs were then removed and lifting eyes in installed so it could be lifted onto the flatbed truck. The impact from the grounding had reduced the distance across the propeller blade tips from 21 to 17 feet. After underwater inspection of the other Enterprise propellers the #1 shaft was inspected to verify that there had been no damage during removal of the old propeller. The shaft taper runout was checked using dial indicators. A mounting fixture was especially fabricated to fit on the strut barrel and hold the three dial indicators. The shaft was then jacked over and readings taken at designated 12,3, 6, 9 o'clock positions and ending again at the 12 o'clock position. Shaft alignment was satisfactory.

WebMaster Bruce