Control and indicating systems
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - International Codes - 1989 MODU Code – Code for the Construction and Equipment of Mobile Offshore Drilling Units, 1989 – Resolution A.649(16) - Chapter 4 – Machinery Installations for all Types of Units - 4.9 Ballast pumping arrangements on column-stabilized units - Control and indicating systems

Control and indicating systems

  4.9.10 A central ballast control station should be provided. It should be located above the worst damage waterline and in a space not within the assumed extent of damage referred to in chapter 3 and adequately protected from weather. It should be provided with the following control and indicating systems where applicable:

  • .1 ballast pump control system;

  • .2 ballast pump status-indicating system;

  • .3 ballast valve control system;

  • .4 ballast valve position-indicating system;

  • .5 tank level indicating system;

  • .6 draught indicating system;

  • .7 heel and trim indicators;

  • .8 power availability indicating system (main and emergency);

  • .9 ballast system hydraulic/pneumatic pressure-indicating system.

  4.9.11 In addition to remote control of the ballast pumps and valves from the central ballast control station, all ballast pumps and valves should be fitted with independent local control operable in the event of remote control failure. The independent local control of each ballast pump and of its associated ballast tank valves should be in the same location.

  4.9.12 The control and indicating systems listed in 4.9.10 should function independently of one another, or have sufficient redundancy, such that a failure in one system does not jeopardize the operation of any of the other systems.

  4.9.13 Each power-actuated ballast valve should fail to the closed position upon loss of control power. Upon reactivation of control power, each such valve should remain closed until the ballast control operator assumes control of the reactivated system. The Administration may accept ballast valve arrangements that do not fail to the closed position upon loss of power provided the Administration is satisfied that the safety of the unit is not impaired.

  4.9.14 The tank level indicating system required by 4.9.10.5 should provide means to:

  • .1 indicate liquid levels in all ballast tanks. A secondary means of determining levels in ballast tanks, which may be a sounding pipe, should be provided. Tank level sensors should not be situated in the tank suction lines;

  • .2 indicate liquid levels in other tanks, such as fuel oil, fresh water, drilling water or liquid storage tanks, the filling or emptying of which, in the view of the Administration, could affect the stability of the unit. Tank level sensors should not be situated in the tank suction lines.

  4.9.15 The draught indicating system should indicate the draught at each corner of the unit or at representative positions as required by the Administration.

  4.9.16 Enclosures housing ballast system electrical components, the failure of which would cause unsafe operation of the ballast system upon liquid entry into the enclosure, should comply with 5.5.21.

  4.9.17 A means to indicate whether a valve is open or closed should be provided at each location from which the valve can be controlled. The indicators should rely on movement of the valve spindle.

  4.9.18 Means should be provided at the central ballast control station to isolate or disconnect the ballast pump control and ballast valve control systems from their sources of electrical, pneumatic or hydraulic power.

Parent topic: 4.9 Ballast pumping arrangements on column-stabilized units
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