1. Documents for approval
Where the pitch-control mechanism is operated hydraulically, two mutually independent, power- driven pump sets are to be fitted. For propulsion plants up to 200 kW, one power-driven pump set is sufficient provided that, in addition, a hand-operated pump is fitted for controlling the blade pitch and this enables the blades to be moved from ahead to the astern position in a short enough time.
Section 11, A to D is to be applied in an analogous manner to hydraulic pipes and pumps.
2. Pitch control mechanism
In the case of the pitch-control mechanism proof is to be furnished that when subjected to impact moments TM as defined by formula (6), the individual
components still have a safely factor of 1,5 relative to the yield strength of the materials used.
! = 3 > = ;! 3 = (
(6)
W06R can be calculated by applying formula 7
W06R = 0,11 · (Bt 2)06R (7)
3. Blade retaining bolts
3.1 The blade retaining bolts shall be designed in such a way as to withstand the forces induced in the even of plastic deformation caused by a force acting on the blade at 0,9R. The bolt material shall have a safety margin of 1,5 against its yield stress. The thread core diameter shall not be less than
' 0 !0 "3 =-
' @ 3 >
(8)
with M0,35R = W!0 "3 · R !0
3.2 The blade retaining bolts are to be tightened in a controlled manner in such a way that the tension on the bolts is about 60 - 70 % of their yield strength. The shank of blade retaining bolts may be designed with a minimum diameter equal to 0,9 times the root diameter of the thread.
3.3 Blade retaining bolts must be secured against unintentionaI loosening.
4. Indicators
Controllable pitch propeller system are to be provided with an engine room indicator showing the actual setting of the blades. Further blade position indicators are to be mounted on the bridge and in the engine room (see also Volume VII and Volume IV Section 9).
5. Failure of control system
Suitable devices are to be fitted to ensure that an alleration of the blade setting cannot overload the propulsion plant or cause it to stall.
Steps must be taken to ensure that, in the event of failure of the control system the setting of the blades - does not change or
- assumes a final position slowly enough to allow the emergency control system to be put into operation.
Controllable pitch propeller systems must be equipped with means of emergency control enabling the controllable pitch propeller to remain in operation should the remote control syslem fail. It is recommended that a device be fitted which locks the propeller blades in the "ahead" setting.
E. Propeller Mounting
1. Tapered Mountings
1.1 Where the tapered joint between the shaft and the propeller is fitted with a key the propeller is to be mounted on the tapered shaft in such a way that approximately the mean torque can be transmitted from the shaft to the propeller by the frictional bond. The propeller nut is to be secured in a suitable manner.
1.2 Where the tapered fit is effected by the hy- draulic oil technique without the use of a key the necessary pull-up distance on the tapered shaft is given by the expression
L1) = L
mech + Ltemp (9)
where Lmech is determined according to the formulae
of elasticity theory applied to shrunk joints for a specific pressure p [N/mm²] at the mean taper diameter found by applying formula (11) and for a water temperature of 35 C. p 2 · T2 f · (c2 · Q2 T2) · T A · f (10) with f = µo S 2 2 Ltemp = · 6 · 10-6 · (35 - t) (11) '
t [ C] The temperature at which the propeller is mounted. Ltemp applies only to propellers made of bronze and
austenitic steel.
1.3 The von Mises’ equivalent stress based on the maximum specific pressure p and the tangential stress in the bore of the propeller hub may not exceed 75 % of the 0,2 % proof stress of yield strength of the propeller material.
1.4 The tapers of propellers which are mounted on the propeller shaft with the aid of the hydraulic oil technique should not be more than 1 : 15 or less than 1 : 20.
1.5 The propeller nut must be strongly secured to the propeller shaft.
2. Flange connections
2.1 Flanged propellers and the bosses of controllable pitch propellers are to be attached using fitted pins and bolts (necked down bolts for preference).
2.2 The diameter of the fitted pins is to be calculated by applying formula (4) given in Section 4, D.4.2.
2.3 The propeller retaining bolts are to be of similar design to those described in D.3.
The thread core diameter shall not be less than
' 0 !0 "3 =-
' @ 3 >
8
F. Vane wheels
1. Dimensioning of vane wheel
1.1 The vane wheel blades are to be dimensioned in such a way that the average material strain in the blade does not exceed 25 N/mm². Mathematical proof thereof is to be submitted to the Society.
1.2 The fitting of a vane wheel must not cause the bending stress in the shafting to exceed 40 N/mm² and the surface pressure in the aft stern tube bearing to exceed 8 bar.
2. Vane wheel bearings
2.1 Design of bearings
The bearing loads used as a basis for dimensioning the antifriction bearings are to be notified to the Society. With regard to these loads the irregular flow against the vane wheel is to be taken into account. As vane wheels bearings two self-aligning roller bearings are to be used. The anti-friction bearings are to be designed such that under the maximale bearing loads occurring in service the theoretical bearing life is at least 40 000 hours.
For the dimensioning of the bearing journal, a calculation of mechanical strength under service conditions is to be submitted.
1) Where appropriate, allowance is also to be made for surface smooting when calculating L.
The vane wheel bearings are to be protected against ingress of seawater by means of suitable seals. An effective rope guard is to be provided to protect the sealing.
2.2 Bolted connections
All bolted connections in the guide wheel and for fixing the vane wheel to the ship are to be tightened in such a way that the utilization of the yield strength of the bolt material does not exceed 70 % and a minimum elongation of 0,15 mm is attained.
2.3 Bearing lubrication
Only those lubricants may be used which ensure adequate lubrication of the anti-friction bearings even with a low water content without reducing the service life of the anti-friction bearings in the period between 2 regular docking intervals of the ship.
The lubricants used must be approved by the Society for lubrication of vane wheel bearings.
3. Position on the ship
3.1 The position of the vane wheel in the shafting and the dimensioning of the clearance between the rudder and the vane wheel must be such that if the vane wheel bearings fail neither the propulsion nor the manoeuvrability of the ship are impaired.
3.2 It must be possible to dismount the vane wheel while the ship is afloat.
G. Balancing and testing
1. Balancing
The finished propeller and the blades of controllable pitch propellers and vane wheels are required to undergo static balancing.
2. Testing
Fixed pitch propellers controllable pitch propellers controllable pitch propeller systems and vane wheels are to be presented to the Society for final inspection and verification of the dimensions.
In addition controllable pitch propeller systems are required to undergo pressure tightness and operational tests.
The Society reserves the right to require non- destructive tests to be conducted to detect surface cracks or casting defects.
With regard to the assessment and the repair of defects in propellers and vane wheels see the Society’s Regulations for the Assessment and Repair of Defects in Propellers.
H [m2] N · 860
18000