6.1 Scope
6.1.1 The requirements of this chapter apply to the design and construction of Directional Control systems. A Directional Control System includes all steering devices, all mechanical, electrical and hydraulic linkages, all power devices, including manual devices, all controls and all actuating systems. Steering may be achieved by means of air or water rudders, foils, flaps, steerable propellers or jets, yaw control ports or transverse thrusters, differential propulsive thrust, variable geometry of the Ship or its lift system components or by a combination of these devices.
6.2 General
6.2.1 Ship should be provided with means for directional control of adequate strength and suitable design to enable the Ship’s heading and direction of travel to be effectively controlled to the maximum extent possible in the prevailing conditions and Ship spaced without undue physical effort at all speeds and in all conditions for which the Ship is to be certified.
6.2.2 Attention is drawn to the possibility of interaction between directional control system and stabilization systems. Where such interaction occurs or where dual purpose components are fitted requirement of the independent circuits of stabilization system and of controllability to be complied with.
6.3 Definitions
6.3.1 Part 4, Chapter 6 of the ‘Rules and Regulations for the Construction and Classification of Steel Ships’ .may be referred for all applicable definitions, installation and location requirements of steering gear compartment..
6.4 Plans and documents
6.4.1 Plans and documents of the steering gear system to be submitted are as follows:
Plans
a) General arrangements of the main and auxiliary steering gears, and of the steering gear compartment.
b) Assembly of upper rudder stock, tiller, tie rod, rudder actuators, etc. as applicable.
c) Construction details of all torque transmitting components of steering gear such as tiller, tiller pin, tiller/rudder stock interference fit mechanism, tie rod, rudder actuator, etc. including bill of materials, welding procedures, non-destructive testing, as applicable.
d) Schematic hydraulic piping diagram, incorporating hydraulic logic diagram and including bill of materials, typical pipe to pipe joint details, pipe to valve joint details, pipe to equipment joint details, pressure rating of valves and pipe fittings and pressure relief valve settings.
e) Steering gear control system, incorporating schematic electrical control logic diagram, instrumentation, alarm devices, etc. including bill of materials.
f) Electrical power supply to power units to steering gear control, including schematic diagram of motor controlled feeder cables, feeder cable electrical protection.
Documents
− Rated torque of main steering gear.
− Calculations of torque-transmitting components
− such as tiller, tie rod, rudder actuator, etc.
6.5 Materials
6.5.1 All the steering gear components and the rudder stock are to be of sound and reliable construction to the Surveyor's satisfaction.
6.5.2 All components transmitting mechanical forces to the rudder stock are to be tested according to the requirements of Part 2 of the ‘Rules and Regulations for the Construction and Classification of Steel Ships’.
6.5.3 Ram; cylinders; pressure housing of rotary vane type actuators; hydraulic power piping;
valves; flanges and fittings; and all steering gear components transmitting mechanical forces to the rudder stock (such as tillers, quadrants, or similar components) are to be of steel or other approved ductile material, duly tested in accordance with the requirements of Part 2 of the ‘Rules and Regulations for the Construction and Classification of Steel Ships’. In general, such material is not to have an elongation of less than 12 per cent nor a tensile strength in excess of 650 [N/mm2]. The use of ductile (nodular) iron castings will be acceptable provided the material has an elongation of not less than 12 per cent.
6.6 Rudder, rudder stock, vanes, tiller and quadrant
6.6.1 Details and scantlings of rudder and rudder stock are to be as per Section 4 above. Maximum permissible jumping clearances and rudder bush clearances are to be clearly mentioned in the drawings and same is to be also clearly indicated in the manuals.
6.6.2 Details and scantlings of vanes, tiller and quadrants are to be as per Part 4, Chapter 6 of the
‘Rules and Regulations for the Construction and Classification of Steel Ships’.
Indian Register of Shipping
6.7 Requirements for design and performance
6.7.1 For design and performance requirements refer to Part 4, Chapter 6 of ‘Rules and Regulations for the Construction and Classification of Steel Ships’. For mechanical steering gear, the requirements given in 6.8 would apply.
6.7.2 In Ship with Rule rudder stock diameter of 120 mm and above the main steering gear is to be power operated.
6.7.3 Where manual power wheel steering is fitted an alternative means of steering which may be a hand tiller is to be readily available and the performance of both systems are to be in accordance with Part 4, Chapter 6 of ‘Rules and Regulations for the Construction and Classification of Steel Ships’.
6.8 Mechanical steering gear
6.8.1 Steel-wire rope, chain and other mechanical systems, when these are used for rudder stock diameters of 120 [mm] and less but excluding allowance for strengthening in ice, will be specially considered. In general the breaking strength of rods/chains etc. is not to be less than :
] [ R Qr 6 strength
Breaking = N
Where,
R = the distance [m] from the point of application of the effort on the tiller to the centre of rudder stock.
Qr = rudder torque [N-m], calculated as per Part 3, chapter 14, Section 3.2 of the ‘Rules and Regulations for the Construction and Classification of Steel Ships’.
6.8.2 Sheaves: Sheaves are to be of ample size and so placed as to provide a fair lead to the quadrant and avoid acute angles. Parts subjected to shock are not to be of cast iron. Guards are to be placed around the sheaves to protect against injury. For sheaves intended to use with ropes, the radius of the grooves is to be equal to that of the rope plus 0.8 mm (1/32in) and the sheave diameter is to be determined on the basis of wire rope flexibility. For 5 x 37 wire rope, the sheave diameter are to be not less than 18 times that of the rope. For wire ropes of lesser flexibility, the sheave diameter is to be increased accordingly. Sheave diameters for chain are to be not less than 30 times the chain diameter.
6.8.3 Buffers : Steering gears other than hydraulic type are to be designed with suitable buffer arrangement to relieve the gear from shocks to the rudder.
6.9 Control and monitoring
6.9.1 The controls and monitoring systems are to be designed in accordance with Part 4, Chapter 6 of ‘Rules and Regulations for the Construction and Classification of Steel Ships’.
6.9.2 The alarms and safeguards Ship of less than 150 GT are to be adequate for the type of steering system employed. See Table 6.9
6.9.3 Ships of less than 150 GT need not be provided with two exclusive electrical circuits for steering gear.
Table 6.9
Item Alarm Note
Angular position of the steering mechanism
- Indication
Steering power units, power Failure -
Steering motors Overload single
phase
Also running indication on bridge
Control system power Failure -
Steering gear hydraulic oil tank level Low
Auto pilot Failure Running
indication
Hydraulic oil temperature High Where oil
cooler is fitted