The corrosion behavior of such materials composing a ship as Ti-6Al-4V for propeller shaft, an Al-Mg alloy for body and Al-bronze for propeller are investigated. A kind of Al-Zn-Ga alloy is found out to be a good sacrificial anode. The good properties are proved by a corrosion test in real sea water for a year, too. A crevice corrosion test is carried out to check the corrosion behavior of propeller shaft coupled with a kind of stainless steel, and proved to be no problem. The effects of hydrogen absorption on the mechanical properties of Ti-6Al-4V is examined, and it shows no change up to about 1000ppm in the case of specimen absorbing it uniformly. The size effect of fatigue strength of Ti-6Al-4V is proved to be no more than that of steels. The propagation rate of fatigue crack in synthetic sea water is proved to be equal to that in air, if Ti-6Al-4V is applied under cathodic protection.
On the former report, loss coefficients of various type valves of 200 mm bore were compared and discussed. In the case of butterfly valve, loss coefficients are mainly affected by valve bore, disc shape and disc thickness ratio for valve bore. In this report, the effects of disc thickness and disc shape on the loss coefficients for 200 mm bore butterfly valves are investigated and the effect of opening ratio on the coefficient at partial open and cavitation points are discussed. At valve full open, the coefficients increase according to the increase of disc thickness, but change is irregular by the shape effect. As per disc shape, the coefficient with spindle shape disc is 40% smaller than that with projection type disc having same thickness. At partial open, the coefficients are put in order by the opening ratio.
The new type of sealing system is based on the idea that lube oil pressure in the stern tube is always lower than sea water pressure, whereby complete no oil leakage is achieved and sea water ingress into the stern tube is also checked step by step. By applying the “High Specific Gravity Oil” with this system which have higher specific gravity than sea water, sea water ingressed into the stern tube aft seal can be automatically separated upward by the difference of specific gravity, and collected through the lube oil piping line. The paper reports as to experimental study of the “High Specific Gravity Oil” concerning to load carrying capacity, water separating property, hydrolic stability & aptitude to seal ring materials, and the simulation test supposing sea water ingress into the stern tube aft seal. Some highlighted aspects are that the system can be engaged with no oil leakage and no bearing damage. As a result, the New Type of Sealing System applying the “High Specific Gravity Oil” is confirmed to be excellent for the prevention of oil pollution.
The temperature rise characteristics of the induction motor can be calculated, if the copper loss, the iron loss and thermal model constants are given. Thermal model constants include thermal conductivity from coil to core (λcf), heat transfer coefficient from coil to air (λca), heat transfer coefficient from core to air (λfa ), λa ≡λcf+λca, λb≡λcf+λfa, thermal unit capacities of coils (Hc) and iron cores (Hf) . The time constant of temperature rise of the induction motor increases with the load increasing. In this case, values of Hc and Hf are made to hold constant and λa, λb and λcf decrease as the load increases. In this paper, the temperature rise characteristics of the continuous operation, intermittent operation and the repeated on-off operation are analyzed and calculated by using the afore mentioned method.
This report describes investigation of tow-boat traulers in the east china sea with medium-speed diesel engines burning blended fuel of Bunker C and marine diesel oil to save the fuel cost. Performance and maintenance of engines were investigated and compared economical efficiency of blended fuel with marine diesel oil on fishing boat engine. Running the engines in its standard marine diesel oil form except for fuel heater and Stellite-face exhaust valves on blended fuel proved to increase exhaust temperature and specific fuel consumption. Maintenance interval of valve, injector and turbo-charger reduce about a half period in comparison with burning marine diesel oil. However satisfactory results was obtained on newly-built fishing boat with new engine which had sufficiently considered the counterplan for low quality fuel.