2.5.1 Flange couplings
The fillet radius at the base of solid forged flanges is to be not less than 0,08 times the actual shaft diameter.
The fillet may be formed of multi-radii in such a way that the stress concentration factor will not be greater than that for a circular fillet with radius 0,08 times the actual shaft diameter.
For non-solid forged flange couplings, the above fillet radius is not to cause a stress in the fillet higher than that caused in the solid forged flange as above.
Fillets are to have a smooth finish and are not to be recessed in way of nuts and bolt heads.
The strength of coupling bolts of the propeller boss to the flange is to be equivalent to that of the aft part of the propeller shaft.
They are to be carefully fitted and shrunk on to the shafts, and the connection is to be such as to reliably resist the vibratory torque and astern pull.
d : Rule diameter of solid intermediate shaft, in mm, taking
into account the ice strengthening requirements of Pt E, Ch 8, Sec
3, where applicable nB : Number of fitted coupling bolts DC : Pitch circle diameter of coupling bolts, in mm Rm : Value of the minimum tensile strength of intermediate shaft
material taken for calculation of d, in N/mm2 RmB : Value of the minimum tensile strength of coupling bolt
material, in N/mm2. Where, in compliance with [2.1.1],
the use of a steel having RmB in excess of the limits
specified in [2.1.4] is
allowed for coupling bolts, the value of RmB to be introduced
in the formula is not exceed the above limits.
To this end, the torque based on friction between the mating surfaces of flanges is not to be less than 2,8 times the transmitted torque, assuming a friction coefficient for steel on steel of 0,18. In addition, the bolt stress due to tightening in way of the minimum cross-section is not to exceed 0,8 times the minimum yield strength (ReH), or 0,2 proof stress (Rp 0,2), of the bolt material.
Transmitted torque has the following meanings:
The value 2,8 above may be reduced to 2,5 in the following cases:
2.5.2 Shrunk couplingsNon-integral couplings which are shrunk on the shaft by means
of the oil pressure injection method or by other means may be accepted
on the basis of the calculation of shrinking and induced stresses,
and assembly instructions.
To this end, the force due to friction between the mating surfaces is not to be less than 2,8 times the total force due to the transmitted torque and thrust.
The value 2,8 above may be reduced to 2,5 in the cases specified under item e) of [2.5.1].
The values of 0,14 and 0,18 will be taken for the friction coefficient in the case of shrinking under oil pressure and dry shrink fitting, respectively.
In addition, the equivalent stress due to shrinkage determined by means of the von Mises-Hencky criterion in the points of maximum stress of the coupling is not to exceed 0,8 times the minimum yield strength (ReH), or 0,2% proof stress (Rp0,2), of the material of the part concerned.
The transmitted torque is that defined under item e) of [2.5.1].
For the determination of the thrust, see Ch 1, Sec 8, [3.1.2].
2.5.3 Other couplingsTypes of couplings other than those mentioned in [2.5.1] and [2.5.2] will be specially considered by the Society.
2.5.4 Flexible couplings
In stiff transmission conditions with the above locking device, a sufficiently wide speed range is to be provided, free from excessive torsional vibrations, such as to enable safe navigation and steering of the ship. As an alternative, a spare flexible element is to be provided on board.
2.5.5 Propeller shaft keys
When these constructional features are intended to obtain an extension of the interval between surveys of the propeller shaft in accordance with the relevant provisions of Pt A, Ch 2, Sec 2, [5.5], they are to be in compliance with Fig 1.
Different scantlings may be accepted, provided that at least the same reduction in stress concentration is ensured.
The fillet radius at the bottom of the keyway is to be not less than 1,25% of the actual propeller shaft diameter at the large end of the cone.
The edges of the key are to be rounded.
The distance from the large end of the propeller shaft cone to the forward end of the key is to be not less than 20% of the actual propeller shaft diameter in way of the large end of the cone.
Key securing screws are not to be located within the first one-third of the cone length from its large end; the edges of the holes are to be carefully faired.
d : Rule diameter, in mm, of the intermediate shaft calculated
in compliance with the requirements of [2.2.2],
Rm = 400 N/mm2
dPM : Actual diameter of propeller shaft at mid-length of the
key, in mm.
|Symbol conventionH = High, HH = High high, G = group
L = Low, LL = Low low, I = individual alarm
X = function is required, R = remote
|Identification of system parameter||Alarm||Indication||Slow-down||Shut-down||Control||Standby Start||Stop|
|Temperature of each shaft thrust bearing|
(non applicable for ball or roller bearings)
|Stern tube bush oil gravity tank level||L|
|Clutches lubricating oil temperature||H||X|
|Clutches oil tank level||L|