Section 2 Propulsion System

201. Propulsion system

1. The material of shafts is to be of mild steel, stainless steel, bronze or monel and the tensile strength of the material is not to be less than 45kgĤmmË. The shafts are to be made of forged or

rolled steel and pressed steel is not to used for shaft.

2. Propeller shaft or stern tube of mild steel is to be of construction which is not to be contacted with sea water, such as continuos bronze sleeve. However, the above requirements are not apply to

the oil lubricating system with approved oil sealing device. The part between stern tube and brack- et is to be protected from contact with sea water using approved paint.

3. In case propeller shafts or stern tube shafts are made of corrosion resistance steel such as stainless steel, bronze or monel, the measurement to prevent from contact with sea water is not needed.

4. The diameter of intermediate shaft(ẀŊ ) is not to be less than that obtained from following formula.

Ĭ

Ė JĂ

ẀŊ G ËŊË ŸJ

(mm)

Ă : Continuous maximum output of engine (PS)

Ÿ : Continuous maximum revolution of shaft (rpm)

5. The diameter of propeller shaft or stern tube shaft (dp) is not to be less than that obtained from following formula.

ẀỲ G ËĦËẀŊ (mm)

ẀŊ : Required diameter of intermediate shaft (mm)

6. Where the propeller shafts or stern tube shafts used the materials of which the tensile strength ex- ceeds 45 kgĤmmË , the diameter of propeller shafts or stern tube shafts may be reduced to the value

multiplied by K of following formula.

However, the propeller shafts or stern tube shafts made of mild steel are not allowed to reduce the

diameter even if the materials of high tensile steel are used.

Ä G Ė

JĖÈ JË

ĖÈ Ğ J FÅ G ĖÈF

Å : minimum tensile strength(kgĤmmË)

7. The thickness of bronze sleeves used in propeller shaft or stern tube shaft is not to be less than that obtained from following formula.

ŹË GŊĦŊĖẀỲĞĒĦŊ ŹË GŊĦĒÈŹË

(mm)

(mm)

Ch 8 Machinery Installations Ch 8

ŹË : thickness of sleeve where stern tube or strut bearings

ŹË : thickness other than above

are contacting

ẀỲ : Required diameter of propeller or stern tube in calculating (mm)

8. In case of propeller shaft set sleeve, the construction between propeller and propeller shaft is to be prevented sea water from ingress.

9. The diameters of coupling bolts at contacting surface of shaft coupling are not to be less than that obtained from following formula. However, in case of material of which tensile strength exceeds 45 kgĤmmË, the diameters may be reduced to the values which are deemed appropriate by the Society.

JẀĖ

Ŋ (mm)

ẀẄ G ŊĦĒÈĬJŸǼ

10.

11.

ẀŊ : Required diameter of intermediate shaft in calculating (mm)

Ÿ : Number of coupling bolts

Ǽ : Diameter of pitch circle (mm)

The thickness of coupling on pitch circle is not to be less than the required diameter of coupling bolt in calculating. However, the coupling thickness of propeller shaft is to be greater than 0.25 times of required diameter of intermediate shaft. Also, the radius of roots in coupling is to be greater than 0.125 times of shaft diameter. In case, the coupling is fabricating type, it is to be of the structure to withstand in full astern condition.

The bearing length of stern tube or strut bracket supporting propeller shaft is not to be less than 4 times of required propeller shaft diameter in calculating.

12. Where the propeller bearing is a lignumbite or approved synthetic material, it is to be designed to lubricate by sufficient sea water. In relatively large stern tube bearing system, it is needed to sup- ply sea water by circulating pump or other water pressure for lubricating.

13.

The stern tube and propeller brackets are to be rigidly fitted with hull structures to maintain shaft

centerline in normal voyage condition. And, where the length of shaft is long, the bearings are to

be supported so that the space between bearings is not be too long. The bearings installed below engine room upper plate are to be readily accessible.

14. The machinery installation and shaft centerline is to be confirmed by the surveyor in crafts afloat condition.