Section 2 Performance

2.1 General

2.1.1 Unless the main steering gear comprises two or more identical power units, in accordance with Pt 5, Ch 19, 2.1 General 2.1.4 or Pt 5, Ch 19, 8.1 For oil storage units of 10 000 tons gross and upwards and every other unit of 70 000 tons gross and upwards 8.1.1, every unit is to be provided with a main steering gear and an auxiliary steering gear, in accordance with the requirements of the Rules. The main steering gear and the auxiliary steering gear are to be so arranged that the failure of one of them will not render the other one inoperative.

2.1.2 The main steering gear and rudder stock is to be:

Of adequate strength and capable of steering the unit at maximum ahead service speed, which shall be demonstrated in accordance with Pt 5, Ch 19, 7.2 Trials;
Capable of putting the rudder over from 35° on one side to 35° on the other side with the unit at its deepest sea-going draught and running ahead at maximum ahead service speed and under the same conditions, from 35° on either side to 30° on the other side in not more than 28 seconds;
Operated by power where necessary to meet the requirements of Pt 5, Ch 19, 2.1 General 2.1.2 and in any case when the Rules, excluding strengthening for navigation in ice, require a rudder stock over 120 mm diameter in way of the tiller; and
So designed that they will not be damaged at maximum astern speed; however, this design requirement need not be proved by trials at maximum astern speed and maximum rudder angle.

2.1.3 The auxiliary steering gear is to be:

Of adequate strength and capable of steering the unit at navigable speed and of being brought speedily into action in an emergency;
Capable of putting the rudder over from 15° on one side to 15° on the other side in not more than 60 seconds with the unit at its deepest sea-going draught and running ahead at one half of the maximum ahead service speed or 7 knots, whichever is the greater; and
Operated by power where necessary to meet the requirements of Pt 5, Ch 19, 2.1 General 2.1.3 and in any case when the Rules, excluding strengthening for navigation in ice, require a rudder stock over 230 mm diameter in way of the tiller.

2.1.4 Where the main steering gear comprises two or more identical power units, an auxiliary steering gear need not be fitted, provided that the main steering gear is arranged so that, after a single failure in its piping system or in one of the power units, the defect can be isolated so that steering capability can be maintained or speedily regained.

2.1.5 Main and auxiliary steering gear power units are to be:

Arranged to restart automatically when power is restored after power failure;
Capable of being brought into operation from a position on the navigating bridge. In the event of a power failure to any one of the steering gear power units, an audible and visual alarm is to be given on the navigating bridge;
Arranged so that transfer between units can be readily effected.

2.1.6 Where the steering gear is so arranged that more than one power or control system can be simultaneously operated, the risk of hydraulic locking caused by a single failure is to be considered.

2.1.7 A means of communication is to be provided between the navigating bridge and the steering gear compartment.

2.1.8 Steering gear, other than of the hydraulic type, will be accepted provided the standards are considered equivalent to the requirements of this Section.

2.2 Rudder angle limiters

2.2.1 Power-operated steering gears are to be provided with positive arrangements, such as limit switches, for stopping the gear before the rudder stops are reached. These arrangements are to be synchronised with the gear only and not with the steering gear control.