Various water droplet separators are being used in power plants, chemical plants and others. Of these separators, the eliminator, which is made of thin plates bended to make zig-zag flow passages, is comparatively simple and high performance. In this report, the separation performance of the eliminator is theoretically analysed. The efficiency ηd, of catching water droplets is given by the following equation: ηd=DN(β)/p* where, DN(β)=1-β/1n(1/β)(1+1-βN/1+β) N = number of bending If N is an odd number, use N-1 instead of an index number N. β= function of water droplet diameter, air velocity, bending plate length and bending angle p= dimensionless pitch of eliminator The separation efficiency is 100% for water droplets which are larger than the droplet diameter satisfying DN (β) = p. In other words, such droplets will be separated completely. If the size distribution of droplets is known at the inlet to the eliminator, the separation efficiency ηN of the eliminator is given by the following equation: ηN=1-Σf(1-ηd)Dp where, f = size distribution of droplets at the inlet to the eliminator.
Careful attentions have been paid to boiler and feed water treatment in case of operating the pressure of 100 kg/cm2 class marine boilers installed on the tanker“Idemitsu Maru”, for the purpose of minimizing damage to the inner surface of boiler tubes due to an obstruction of heat transfer by scaling and alkali corrosion. Some investigations concerning scale formation on the inner surface of boiler tubes have been continued to cross check the above mentioned water treatment. The results are as follows. (1) After 8 years operation, the max. inner scale mass is only about 50 mg/cm2and the location is the fire-side of rear water wall panel, 3300-3400 mm hight from furnace floor level. This boiler and feed water treatment will be certainly satisfactory for the protection from obstruction of heat transfer by scaling. (2) The alkali corrosion on the inner surface of boiler tubes after descaling is not observed at all. This boiler water treatment will be certainly satisfactory for the protection of alkali corrosion. (3) The formation rate of inner scale on the fire-side is approximately two times compared with anti-fire side of rear water wall panel for both reheat and straight boilers. (4) The formation rate of inner total scale and Fe3O4of its main component increases exponentially, but ZnO and Cu component in the scale picked up from feed water system and PO4component deposited from boiler water increase linearly. However, the formation rate of CaO, MgO and SiO2component increases little anti-exponentially. This increasing rate may depend upon slightly delayed regeneration of ion exchange resin for make up water.
Many studies on gear have been done in the past, and many papers have been published. However many of them were on the theory of gear shape, the problems on pitting and scouring, on vibration, and the prevention of noise, a few study has been conducted on fatigue strength of gear. In this paper the fatigue strength of the large sized reduction gear used in marine-transmission is discussed, and summarized as follows; 1) Fatigue test results with the smooth and notched specimen of the actually used material having 1% Cr-Mo and 3% Cr-Mo, and on the influence of heat treatment on the fatigue strength were given. 2) The method of estimating the stress-number of frequency curve for the fatigue life prediction was proposed. 3) The method of fatigue life prediction was proposed, and was dependent on the combination of S-N curves and stress-number of frequency curves. 4) The problems on the fatigue strength of gear to study in future were also explained.
For the propeller material, manganese or aluminum bronze have been generally used for many years. In recent years, these bronze propellers have been often suffered from corrosion due to polluted sea water and damaged by cavitation-erosion in high-speed ships mainly. In order to overcome this matter, it has required to develop new material which has excellent resistance of corrosion and cavitation-erosion, and high mechanical and corrosion fatigue strength for marine propellers. To cope with this situation, comprehensive research work has been carried out on the various stainless steel and found the new stainless steel called KS-2 which can surely meet the requirement to advanced material for marine propellers. In this report, various properties of KS-2, such as resistance of corrosion and cavitation-erosion, mechanical property, weldability and corrosion fatigue strength are described with test results on an actual blade. In addition, the result on a propeller in an actual ship test is also included.
The adoption of keyless propellers in Nippon Kaiji Kyokai classed ships first came in 1971, somewhat later than in other countries. Up to the end of 1976, more than 80 ships have been fitted with keyless propellers, all of which have shown excellent results in operation and 10% of which, having had shaft surveys by taking off the propellers, have shown satisfactory results on the contact surfaces. The value in adopting keyless propellers and the actual results in operation are described in this paper.
On March 1976, M/T TOEIMARU, 36000 Dead Weight tanker succeeded her three years of operation with none of her main engine piston's overhauled in that period and is now challenging four years non-overhaul operation. Cylinder liner wear rate during the period is 0.02-0.03mm/1000hrs and estimated piston ring wear is 0.05-0.15mm/1000hrs at the top ring. In this paper, the detail of operation and inspection results and also improved points for the long term non-overhaul operation is reported.
Recently it is conspicuous that the increasing tendency of the capacity of the ship's AC power system adopted to the large vessel like container ship. So it is easy to predict that the greater the electric power capacity becomes, the larger the leakage current between the power circuit and the hull increases according to the large changes of electrostatic capacitance C and small leakage resistance ρ. This paper describes the measured results of the arcing grounded current of non-grounding three-phase power system for ships service, and the relationships between the electric power capacity P and the leakage circuit parameters C and ρ, and the direct arcing grounded current IR0 and safety voltage VB. It is confirmed that the leakage parameters C and ρ can be estimated by the electric power capacity P. Consequently it may be suggested that a given value of P can give not only the values of IR0 and VB but also the relationship between the grounded resistance RG and VB for the non-grounded electric power system.