Tsuyoshi Kawazoe

Corrosive Wear of Bronze Propeller Shaft Sleeve (Part 2; Wear Control by Cathodic Protection and Application to an Actual Ferry)

The previous report described corrosive wear of propeller shaft sleeves made of bronze in seawater-lubricated stern tube bearings, as well as the occurrence of craters on the sleeve surface due to the action of erosion corrosion. Based on the mechanism, this second report provides the development of an impressed current cathodic protection method that prevents the corrosion of the sleeve surface and reduces wear. Using Pt/Ti anodes installed in some of the water channel grooves for the rubber bearings, this method is characterized by intermittent protection, and protection conditions were investigated by means of fundamental tests using bearings 140 mm in diameter. As a result, a current density of 8 A/m 2 was found to protect the sleeve from corrosion, and it was confirmed that the sleeve wear was reduced. Cathodically protected bearings were applied to bearings 500 mm in diameter equipped for an actual ferry vessel, and the results are presented here in terms of bearing design, trial running, and in-service progress. Presented at the STLE Annual Meeting, in Toronto, Ontario, Canada, May 17-20, 2004, Review led by Jim Netzel

Corrosive Wear of Bronze Propeller Shaft Sleeve (Part 1; Investigation of the Sleeve Used and Fundamental Corrosive Wear Test)

As propeller shaft diameters of ferries become larger in conjunction with higher vessel speed and equipping with CPPs (controllable pitch propellers), the life duration of a stern tube bearing under seawater lubrication has a tendency to be reduced. The wear of the propeller shaft sleeve is typically greater than that of the rubber bearings, with triangularly shaped craters appearing on the sleeve surface. In this paper, we describe the investigation of a used sleeve sample taken from an actual vessel, as well as the wear characteristics of various bronze alloys examined by conducting corrosive wear testing under sliding conditions equivalent to actual ferry service. The results indicated that corrosive wear was the main cause of sleeve wear and, based on comparisons between the amount of wear in seawater and in distilled water, the influence of corrosion on sleeve wear was found to be substantial. Also, the craters are considered to be formed by erosion corrosion. In a follow-up report, cathodic protection is applied to the sleeve as a countermeasure based on the mechanism, and the wear characteristics are reported together with the application to an actual vessel. Presented at the STLE Annual Meeting, in Toronto, Ontario, Canada, May 17-20, 2004, Review led by Jim Netzel

Development of Multi-Connected Floating Body System

A multi-connected floating body system composed of many connected small-scale floating body units has a number of advantages with regard to construction and performance. To realize the multi-connected floating body system, a new type of mechanical connecting device was developed. It is composed of multi-degrees of freedom connecting mechanism and restricting mechanism to control a restricting condition between floating body units, and its effectiveness was confirmed by model basin test in waves. Next, friction and wear tests in the seawater environment led to the discovery of suitable materials for oscillatory sliding parts in multi-degrees of freedom connecting mechanism. Finally, a field test performed for two floating body units connected by use of the mechanical connecting device proved that the developed mechanical connecting device was of practical use.Copyright

Sliding Wear Characteristics of Anticorrosive Platings in Artificial Seawater

The objective of this study is to evaluate sliding wear resistance of anticorrosive Ni and Cr base electroplatings and Ni-P electroless plating in seawater. Sliding wear tests against Al2O3 and bearing steel (SUJ2) were carried out in artificial seawater using an electrochemical potentiostat. Friction and wear were measured, and the wear track and the corrosion products at the contact were analyzed by SEM and ESCA. As the results, the corrosive wear of the platings is affected by material properties of the counterface. Under the electrode and catholic potentials for practical use, Ni base platings show more superior corrosive wear resistance than Cr base platings sliding against Al2O3. In the case of the counterface of SUJ2, the corrosive wear hardly occurs on the platings except for Ni-P electroless plating. Main factors of the surface damage within this experimental condition are anticorrosion of the platings and adhesion between the platings and the counterface.

Friction of Wire Rope in Cable Puller.

It is very important for a cable puller to grasp a wire rope tightly without any slippage and with no damage on both of the rope surface and cable gripper. The friction mechanism of a wire rope under a large deformation due to high grasp force, however, has not been sufficiently clarified. The present paper will report some results on friction of the wire rope under high compressive load on some cases such as under lubricated condition and under different contact conditions using three types of wire rope with steel core, fiber core and a galvanized rope with fiber core. As the results, the difference of contact area between the wire rope and gripper greatly affects the friction behavior; that is, the gripper with a curved surface can bring large friction force comparing with the gripper with a flat surface owing to its large real contact area, which is dominated by a restriction of the escape of wire between gripper surfaces and the deformation of a rope and a core.

Development of Mitsubishi Marine Propeller

Due to the strong demands for energy saving and improved habitability of ships, design of propellers with higher efficiency and lower cavitation induced excitation is recognized to be most impotant, together with matching of the propeller with the given engine and ship performances.Under these circumstances, MHI developed propellers with integrated performances called MAP (Mitsubishi Advanced Propellers), together with a new stainless type propeller material called MCRS (Mitsubishi Corrosion Resistance Steel), intending not only improved performances but also reduced propeller weight.