7.5 Steering gear
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Statutory Documents - IMO Publications and Documents - International Codes - 1979 MODU Code – Code for the Construction and Equipment of Mobile Offshore Drilling Units – Resolution A.414(XI) - Chapter 7 – Machinery and Electrical Installations for Self-propelled Units(See also 4.1) - 7.5 Steering gear

7.5 Steering gear

  7.5.1

  • .1 Except as provided in 7.5.2, units should be provided with a main steering gear and an auxiliary steering gear to the satisfaction of the Administration. The main steering gear and the auxiliary steering gear should be so arranged that a single failure in one of them so far as is reasonable and practicable will not render the other one inoperative.

  • .2 The main steering gear should be of adequate strength and sufficient to steer the unit at maximum service speed and this should be demonstrated. The main steering gear and rudder stock should be so designed that they will not be damaged at maximum astern speed but this design requirement need not be proved by trials at maximum astern speed and maximum rudder angle.

  • .3 The main steering gear should, with the unit at her deepest sea-going draught, be capable of putting the rudder over from 35 degrees on one side to 35 degrees on the other side with the unit running ahead at maximum service speed. The rudder should be capable of being put over from 35 degrees on either side to 30 degrees on the other side in not more than 28 seconds, under the same conditions.

  • .4 The main steering gear should be operated by power where necessary to fulfil the requirements of 7.5.1.3 and in any case in which the Administration would require a rudder stock of over 120 millimetres diameter in way of the tiller.

  • .5 The main steering gear power unit(s) should be arranged to start automatically when power is restored after a power failure.

  • .6 The auxiliary steering gear should be of adequate strength and sufficient to steer the unit at navigable speed and capable of being brought speedily into action in an emergency.

  • .7 The auxiliary steering gear should be capable of putting the rudder over from 15 degrees on one side to 15 degrees on the other side in not more than 60 seconds with the unit at its deepest sea-going draught while running at one half of its maximum speed ahead or seven knots, whichever is the greater.

  • .8 The auxiliary steering gear should be operated by power where necessary to fulfil the requirements of 7.5.1.7, and in any case in which the Administration would require a rudder stock of over 230 millimetres diameter in way of the tiller.

  • .9 Where the main steering gear comprises two or more identical power units an auxiliary steering gear need not be fitted if the main steering gear is capable of operating the rudder as required by 7.5.1.3 while operating with all power units. As far as is reasonable and practicable the main steering gear should be so arranged that a single failure in its piping or in one of the power units will not impair the integrity of the remaining part of the steering gear.

  • .10

    • .1 Control of the main steering gear should be provided both on the navigating bridge and in the steering gear compartment. The steering gear control system which provides for control from the navigating bridge, if electric, should be supplied from the steering gear power circuit from a point within the steering gear compartment.

    • .2 When the main steering gear is arranged according to 7.5.1.9 there should be two independent control systems provided, each of which can be operated from the navigating bridge. Where the control system comprises a hydraulic telemotor, the Administration may waive the requirement for a second independent control system.

    • .3 Where the auxiliary steering gear is power operated, it should be provided with a control system operated from the navigating bridge and this should be independent of the control system for the main steering gear.

    • .4 Means should be provided in the steering gear compartment to disconnect the steering gear control system from the power circuit.

  • .11 A means of communication should be provided between the navigating bridge and the steering gear compartment.

  • .12

    • .1 The exact angular position of the rudder, if power operated, should be indicated on the navigating bridge. The rudder angle indication should be independent of the steering gear control system.

    • .2 The angular position of the rudder should be recognizable in the steering gear compartment.

  • .13 An alternative power supply, sufficient at least to supply a steering gear power unit which complies with the requirement of 7.5.1.7 and also its associated control system and the rudder angle indicator, should be provided, automatically, within 45 seconds, either from the emergency source of electrical power, or from another independent source of power located in the steering gear compartment. This independent source of power should be used only for this purpose and should have a capacity sufficient for 10 minutes of continuous operation.

  7.5.2 Where a non-conventional rudder is installed the Administration should give special consideration to the steering system, so as to ensure that an acceptable degree of reliability and effectiveness which is based on 7.5.1 is provided.

Parent topic: Chapter 7 – Machinery and Electrical Installations for Self-propelled Units(See also 4.1 )
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