The rotors and casings of the four astern turbines were all partially rebladed in place in the ship.
The dummy ring and piston were found broken in the port H. P. astern; but these were renewed and machined in place, the jacking engine turning the rotor while a cutting tool was attached to the flange of the casting, thus making a lathe out of the turbine and solving the practically impossible problem of removing the rotor from the ship to be placed in a lathe ashore.
It was found that the impulse stages in this turbine had been the cause of the damage to this dummy, so it was decided to remove the impulse stages entirely, which was done. This decreases the economy of the turbine, but the safety guarantee to the successful operation of this unit so far overbalanced this factor that economy was sacrificed.
The starboard H. P. astern casing had several bad cracks in both top and bottom, and from records on board had not been in use on the last voyage of the vessel. This was in process of being electrically welded when I reported on board. The method in use, however, proved later on test, to give a faulty weld, so that it was decided to cut a deep “V” groove in the cracks and lace with steel studs, the lacing being filled in with the weld, thus giving the weld holding power due to the welding material fusing with the studs. This machine operated successfully during the entire commission of the vessel with no signs of ruptures or faulty welds.
On examination of the main throttles the starboard H. P. astern throttle spool was found to be broken and off the stem. This throttle was renewed and operated satisfactorily.
The system of automatic control of feed pumps in the engine room by float and pressure control was decided on as being highly dangerous, this system was at once removed and hand control of pumps substituted.
After operating for some time it was found impossible to obtain a vacuum that would afford economical operation for a turbine plant. The capacities of the pumps and condensers were computed and checked up and found adequate for the horsepower to be handled. The low pressure system was then tested out by water pressure and every noticeable leak stopped. This however gave us no better results, the best vacuum we could obtain averaging around 27 inches under normal operating conditions. The question of the wet and dry suctions of the pumps was next taken into consideration and it was decided to blank the dry suction off from the condenser and lead it into the wet suction of its own pump. This was done and with the results desired. The vacuum desired can be obtained at all times. With circulating water at forty degrees a vacuum of as high as twenty-nine inches has been obtained. The average vacuum under all conditions obtained since this change is about twenty-eight inches.
Gland Steam Turbine Supply
In order to further increase economy a radical change was made in the method of supplying the turbines with gland steam. As installed, all turbine glands required the use of live steam, which with turbines of such large dimensions, was quite an item. By a simple change in pipe leads and valves, the leak off from the H. P. ahead glands, which formerly led to the condenser, was piped to supply the glands of all astern turbines and the I. P. and L. P. ahead turbines, thus utilizing a three-inch line of steam which was formerly wasted in the condenser. It is believed that this vessel is the only vessel afloat that uses this system of gland steam.
The above concludes briefly a history of the major items of alterations and repairs in the engine rooms.