B Lateral Thrust Propellers and Manoeuvring Aids ... 7-5 C Variable Pitch Propellers for Main Propulsion Systems ... 7-6 D Auxiliary Machinery and Systems ... 7-6 E Deck Machinery ... 7-9 F Electrical Heating Equipment and Heaters ... 7-10 G Heel-Compensating Systems ... 7-10 H Cross-flooding Arrangements ... 7-10
A Steering Gear
A.1 General
A.1.1 Every ship shall be provided with two as far as possible independent steering gear systems, as follows:
1 main and 1 auxiliary steering gear
on every tanker, chemical tanker or gas carrier of 10000 GT and upwards and in every other ship of 70 000 GT with 1 main steering gear with two or more identical power units
on every passenger ship with 2 main steering gears
Where electrical or electro-hydraulic steering gear is installed, the following Rules are to be observed.
A.1.2 The design of main and auxiliary steering gears shall conform to SOLAS, Chapt. II-1, Part C, Reg. 29 and 30, and to the GL Rules set out in Machinery Installations (I-1-2), Section 14, A.
A.1.3 The electrical systems of main and auxiliary steering gears shall be so designed that a failure in one of them shall not affect the operation of the other. This also applies when the main steering gear comprises two or more identical power units, and an auxiliary steering gear need not therefore be provid-ed under the SOLAS regulations.
A.1.4 On every tanker, chemical tanker or gas carrier greater than 10 000 GT the main steering gear system shall be so arranged that in the event of loss of steering capability due to a single failure in any part of the power actuating systems of the main steering gear, excluding the tiller, quadrant or compo-nents serving the same purpose, or seizure of the rudder actuators, steering capability shall be regained in not more than 45 s after the loss of one power actuating system. The isolation of the defect part of the system shall be done by automatic means.
A.1.5 For increased vibration loads in the steering gear compartment, see Section 1, E.
A.2 Power supply
A.2.1 The power supply to steering gears is also required to comply with the provisions of Section 4, I.
A.2.2 A separate power supply circuit from the main switchboard is to be provided for each steering gear power unit.
After an electrical power failure, the steering gear power units shall restart automatically when the power is restored.
A.2.3 On ships with a calculated rudderstock of more than 230 mm in diameter (see the GL Rules for Machinery Installations (I-1-2), Section 14, A.4.1), without ice strengthening, an alternative power source additional to the main power source is required, which is capable of supplying the steering gear in such a way that this is able to perform at least the duties of an auxiliary steering gear. It shall also supply the steering gear control system, the remote control of the power unit and the rudder-angle indicator. In addi-tion, the alternative power source shall be automatically connected within 45 s after a power failure. This power source may be the emergency generator set, or an independent power source intended only for this purpose and situated in the steering gear compartment, and shall maintain operation:
for 10 minutes on ships of up to 10 000 GRT and
for 30 minutes on ships of 10 000 GRT and over.
A.2.4 The system is to be so designed that it is possible, from the bridge or the steering gear com-partment, to put each power unit into operation. Mechanically separated switches are to be provided for this purpose.
The supply of the bridge remote control for the power units shall be run from the associated switchgear in the steering gear compartment – same as steering gear control system – and shall be made for its dis-connection without any accessories.
For supplies to the steering gear control systems, see A.6.
A.3 Design of the electric drives
A.3.1 To determine the torque characteristics required for electric motors of power units, account is to be taken of the breakaway torque and the effective maximum torque of the steering gear under all op-erating conditions (see the GL Rules for Machinery Installations (I-1-2), Section 14, A.4).
A.3.2 The following requirements apply to the modes of operation:
A.3.2.1 Steering gear with intermittent power demand:
S 6 - 25 % for converters and the motors of electro-hydraulic drives
S 3 - 40 % for the motors of electromechanical steering gears The ratio of pull-out torque to rated torque is to be at least 1.6 in all cases.
A.3.2.2 Steering gear with constant power demand:
S 1 - 100 % continuous service
A.3.3 For the motor design, see Section 20.
A.4 Switchgear
A.4.1 Each steering gear motor shall have its own separate switchgear. Combined contactor cabi-nets are not permitted.
Each steering gear motor shall have an ammeter mounted in the main or emergency switchboard, as applicable, or in the contactor cabinets.
A.4.2 The remote control systems of the power units and the rudder control shall be capable of be-ing disconnected or isolated inside the contactor cabinets (e.g. by removal of the fuse-links or switchbe-ing off the automatic circuit breakers). These switches or fuses are to be specially marked.
A.5 Protection equipment
A.5.1 The circuits for the control systems and motors of steering gears are to be protected only against short circuits.
A.5.2 Where fuses are used, their current ratings shall be two steps higher than the rated current of the motors. However, in the case of intermittent-service motors, the fuse rating shall not exceed 160 % of the rated motor current.
Section 7 Power Equipment
A.5.3 Protection equipment against excess current, including starting current, if provided, is to be required to be not for less than twice the rated current of the motor so protected. Steering gear motor circuits obtaining their power supply via an electronic converter and which are limited to full load current are exempt from above requirement.
A.5.4 The instantaneous short-circuit trip of circuit breakers shall be set to a value not greater than 15 times the rated current of the drive motor.
A.5.5 The protection of control circuits shall correspond to at least twice the maximum rated current of the circuit, though not, if possible, below 6 A.
A.6 Steering gear control systems
A.6.1 Ships with electrically operated steering gear controls shall have two independent steering gear control systems. Separated cables and wires are to be provided for these control systems.
A common steering wheel or a common tiller may be used.
A.6.2 If a follow-up (FU) control system and a non-follow-up (NFU) control system are provided, each of these systems shall be able to operate on each power unit. Switching of the control systems shall be possible on the bridge.
Where two identical control systems are installed, each control system can be permanently assigned to a power unit.
If a follow-up control system is installed on the bridge wing, then the follow-up tiller shall be fitted with a retaining spring to midship position, or a take-over arrangement shall be installed on bridge wings.
A.6.3 Provision shall be made for operating the main and auxiliary steering gear from the bridge and the steering gear compartment.
A.6.4 The power supplies to the electrical steering gear control systems shall be taken from the power unit supplies in the steering gear compartment, or from the corresponding power unit feeders in the main or emergency switchboard (see A.2.4).
A.6.5 The electrical separation from each other of the steering gear control systems shall not be impaired by the addition of extra systems, such as autopilot systems.
A.6.6 For change-over between different control systems a common control selector switch may be provided. The circuits of the various control systems shall be arranged electrically and physically separat-ed.
A.6.7 On ships where an automatic control system like heading- or track control system is installed, an override facility shall be installed close to the operator unit of the automatic steering system. The Over-ride facility shall be so designed that self-induced return to automatic control is not possible except where the heading preselection of the automatic system is automatically kept in line. The switch-over from au-tomatic- to manual control by "Override" is to be indicated optically and audibly at the steering position.
The override facility shall be independent of the automatic control system or follow-up control mode.
A.6.8 Different steering modes including steering gear control positions on the bridge wings shall be changed over by all poles, when it cannot be verified that it is free of reactive effects. Portable steering consoles are to be connected via plugs with pin coding. It is necessary to ensure that the rudder-angle indicator can be read within the range of operation of the portable steering console.
A.6.9 Repeaters and limit switches - if provided - shall be linked electrically and mechanically to the respective control system and mounted separately to the rudder stock or the adjusting devices.
A.7 Alarms and indicators
A.7.1 Alarms and indicators for steering gears and controls are to be gathered from Table 7.1.
A.7.2 Depending on the rudder characteristic, critical deviations between rudder order and response shall be indicated visually and audibly as actual steering mode failure alarm on the navigating bridge. The following parameters shall be monitored:
Direction: actual rudder position follows the set value;
Delay: rudder´s actual position reaches set position within defined time limits;
Accuracy: the end actual position shall correspond to the set value within the design offset toleranc-es.
A.7.3 The alarms/indicators listed in Table 7.1 shall be signalled visually and audibly irrespective from the automation equipment.
Alarms and indicators on the bridge shall be announced at a position close to main steering station.
A.7.4 In case of fixed relation between control system and power unit the alarms No. 2 and No. 5 of Table 7.1 may be grouped.
A.7.5 The energy supply for the alarms and indicators shall be in accordance with A.2 A.8 Rudder-angle indicator
See Section 9, C.4 A.9 Tests
A.9.1 For the testing of electrical motors, see Section 20.
A.9.2 The following monitoring devices are subject to mandatory type approval:
phase-failure detection
level switches
A.9.3 Steering gear control systems with all components important for the function are subject to a mandatory type approval, e.g.:
steering mode selector switch
follow-up (FU) / non-follow-up (NFU) control devices
rudder angle feedback units, incl. lever drive
Table 7.1 Alarms and indicators of steering gear and controls
No. Alarms/indicators
Main and auxiliary steering gear
Bridge Engine room
1 Operation of power unit
2 Power failure of power unit/control
3 Overload of electric drive or phase failure of supply
4 Low level of hydraulic oil tank
5 Power failure of steering control system
6 Hydraulic lock
7 Failure actual steering mode
Note
= Single indication, see also A.7.3
= Group indication
Section 7 Power Equipment
A.10 Control of steering propeller systems for main propulsion units A.10.1 Control of the direction of thrust
The requirements of A.6 shall be applied in an appropriate manner.
A.10.2 Monitoring and testing
The requirements of A.7 and A.9 shall be applied in appropriate manner.
A.10.3 Indicator
The effect on the course shall be indicated. The regulations in Section 9, C shall be applied in appropriate manner.