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GUIDELINES ON SHAFTING ALIGNMENT phần 9

mà không cần dùng lực lượng nổi trên các cánh quạt vào tài khoản. Khi aftmost mang ống đuôi tàu bao gồm dầu bôi trơn bằng kim loại màu trắng, đánh giá là được làm bằng áp lực mang danh nghĩa cùng với khuynh hướng, hoặc tương đối giữa các trục cánh quạt và ống mang aftmost nghiêm khắc hoặc chịu áp lực tối đa trong ống nghiêm khắc aftmost mang | ClassNK PART B AMENDMENT OF THE GUIDANCE TO THE RULES AND ITS EXPLANATORY NOTES load of other bearings differ from the actual respective values for each bearing. In order to prevent such a situation from occurring the Guidance specifies that calculation results with a negative bearing load are not acceptable. R1 I Unloading ỉ-ị R3 R2 i R3 R2 Figure 3.1 Negative bearing load. 1.3.2 -1 Light Draught Condition Hot Condition This calculation condition is used to examine the strength of the intermediate shaft bearings engine bearings and other bearings in the ship s ballast condition when the propulsion machinery is in the hot condition. It is assumed here that the hull girder deflection is the same as that in the condition described in paragraph 1.3.1 above and that the differences in the change in bearing offsets are only attributable to differences in temperature. Temperature changes cause changes in the offsets of all bearings such as the stern tube bearings intermediate shaft bearings gear shaft bearings engine bearings and the like. However since large offset changes are seen especially on gear shaft bearings and engine bearings temperature changes on at least these bearings are to be considered in the calculation. The amount of the offset change is to be in accordance with the manufacturer s instructions as it varies depending on the manufacturer and their respective models. For main engines an increase in temperature of from 20 to 55 C is generally considered and as shown in Figure 3.2 the resulting change in the bearing offset becomes larger as the scale of the engine bore of the cylinder becomes greater. 0.40 0.30 0.20 0.10 0.00 300 400 500 600 700 800 900 Cylinder bore mm Figure 3.2 Relationship between change in bearing offset and cylinder bore. -2 -3 Buoyancy acting on the propeller changes depending on the extent of immersion of the propeller. However the effect of buoyancy is such a degree that the load on the aftmost stern tube bearing changes only .