Journal of the Kansai Society of Naval Architects, Japan

"Cement carriers" or "cement tankers" are bulk cargo ships which carry cement in bulk. They have become to be noticed in our country after the War, and now are being built one by one, and are serving for almost all of the long way transportation of cement. These ships have some problems awaiting solution caused by the peculiarity of cement and cement industry. In this paper we discuss these problems, and will consider of the fundamental design of these ships. At the next opportunity we will refer to their practical construction and the self-unloading apparatus.

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Capacity of mooring winch must be powerful enough to pull a ship, but unnecessarily powerful winch tends to cause breakage of rope. So, in order to determine suitable winch capacity, the writer examined both load of mooring winch requisite to pull a ship against wind and breaking strength of mooring rope, and consequently next conclusions were obtained. Load of mooring winch and diameter of mooring rope for an ordinary ship may be decided from Fig.2 and Fig.7. In the case of winding rope by warping end of winch, it is not adequate to use wire rope for ships over 150 m. It may be insecure to pull ships over 200 m by only two lines. Maximum load of mooring winch should not exceed about 15t.

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Generally insulation tests are held to confirm the insulation effect of chamber walls after cooling down. From the records with self-recording thermometers during insulation tests, we derived a temperature-hour formula, which can be used to confirm the insulation effect in chambers. We also obtained the values 0.365 and 0.353 kcal/hr m^2℃ as heat transmission coefficient k for refrigerated cargo chambers by the tests in the cargo ships A and B. These values are about 2.2 times as much as the value calculated from conductivity coefficient of each insulation material. Heat transmission is increased by effects of steel structure, e.g. beams, frames and stiffeners, and supporting timbers in insulation walls.

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With the recent tendency to build high speed vessels high powered enginers are installed, and diesel engines are more frequently used than before to meet economic demand. But, one of the problems encountered in the installation of diesel engines is that of reducing the intake noise and exhaust gas noise to acceptable values. Specially the exhaust gas noise is increased with the power up of main engine and affects the surrounding bridge area. Exhaust gas noise has low frequency, peculiar to the large engines, and in some cases the noise exceeds the acceptable values. Although the spectra of the noise which is to be diminished must be thoroughly examined prior to the designing of exhaust gas muffler, such examination has not been extensively made, so that no muffler up to this day has been quite effective. In view of the above situation, spectra of the exhaust gas noise were measured on board and an exhaust gas muffler has been attempted to meet the characteristics revealed by the model tests.

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