Section 5 Ballast system

5.1.1 Units are to be provided with an efficient pumping system capable of ballasting and de-ballasting any ballast tank under normal operating and transit conditions. The system is to be arranged to prevent inadvertent transfer of ballast from one tank or hull to another.

5.1.2 The ballast system is to be arranged so that it will remain operable, and tanks can be effectively de-ballasted through at least one suction, up to angles of inclination as specified in Tables 1.1.1, 1.1.2 and 1.1.3 in Chapter 1, as applicable.

5.1.3 The system is to be designed so that a single failure or mal-operation of any item of equipment or component will not lead to uncontrolled liquid movement. Pumps, piping and control systems should not be situated within the defined damage penetration zones, see Pt 5, Ch 13, 1.2 Prevention of progressive flooding in damage condition of the Rules for Ships.

5.2.1 At least two independently driven ballast pumps are to be provided and arranged so that the system will remain operable in the event of failure of any one pump. Consideration should be given to locating the pumps in separate compartments where, in the event of flooding, fire or other damage in a particular compartment, an alternative pump in an unaffected compartment will be available. Such pumps need not be dedicated ballast pumps, but must be readily available for use on the ballast system at all times.

5.2.2 The capacity of each ballast pump is to be sufficient to provide safe handling and operation of the unit.

5.2.3 Ballast pumps should be self-priming unless it can be demonstrated that this would be unnecessary for the intended application. Pumps of the centrifugal type are to be self-priming by means of an automatic priming system.

5.3.1 Ballast pipes are to be of steel or other approved material. Special consideration should be given to the design of pipes passing through tanks, particularly with regard to the effects of corrosion.

5.3.2 All valves are to be clearly marked to identify their function. Positive indication (open/closed) is to be provided at the valve, and at all positions from which the valve can be controlled. The indicators are to rely on the movement of the valve spindle.

5.3.3 The valves in the ballast system are to be self-closing by mechanical means or be power-operated by either a stored energy system provided with no fewer than two power units, or by an electrical supply system. Consideration should also be given to the need for equipment to operate when submerged.

5.3.4 The closing speed of power-operated valves should be limited where necessary, to prevent excessive pressure surges.

5.3.5 Valves which fail to set position are to be provided with an independent secondary means of closure from a readily accessible position above the damage waterplane. Power failure to sea-water inlet and discharge valves for systems such as cooling for essential machinery or for supply to fire pumps should not result in closing of open valves or in opening of closed valves. Such systems, which require the inlet/discharge valve to fail to a set position, are not to share a common inlet/discharge with systems in which the valves fail closed.

5.3.6 All sea inlet and discharge valves which are submerged at maximum operating draught and are located in normally unattended spaces are to be remotely controlled from a manned control station. Such valves are to fail automatically to the closed position on loss of control or actuating power unless overriding considerations require a valve to fail to set position.

5.4.1 All ballast pumps and power-operated valves are to be fitted with independent local control, which may be manual control, in addition to the remote control from the central control station. The independent local control of each ballast pump and of its associated tank valves should be in the same location. Such local controls are to be readily accessible and, where practicable, their access routes should not be situated within the defined damage penetration zones, see Pt 5, Ch 13, 1.2 Prevention of progressive flooding in damage condition of the Rules for Ships. A diagram of the representative part of the ballast system is to be permanently displayed at each location.

5.4.2 The control systems are to function independently of the indicating systems, or have sufficient redundancy, such that failure of one system does not jeopardise the operation of the other systems.

5.4.3 Valves which have failed closed should, on restoration of power, remain closed until the operator assumes control of the reactivated system.

5.4.4 For requirements relating to control and supervision of unattended ballast pumps located in dangerous or hazardous spaces, see Pt 7, Ch 2, 5.1 General 5.1.8.

5.5.1 The general requirements of Pt 5, Ch 13, 5.1 General requirements to Pt 5, Ch 13, 5.4 Control of pumps and valves are to be complied with unless otherwise specified in this Section.

5.5.2 The ballast system is to have the capability to bring the unit, while in an intact condition, from the maximum normal operating draught to a severe storm draught or a decrease in draught of 4,6 m, whichever distance is greater, within three hours.

5.5.3 In the damage condition, see Pt 4, Ch 7, the system is to have the capability of restoring the unit to a level trim and safe draught condition without taking additional ballast and with any one pump inoperable.

5.5.4 The ballast system sea-water inlets and discharges should be separate from those of other systems.

5.5.5 Ballast system manifolds are to be arranged such that a specially defined operational procedure must be carried out when ballast is transferred from one end or side of the unit to the other.

5.6.1 Ballast water treatment systems are to comply with Pt 5, Ch 25 Ballast Water Treatment System and Installation.

5.6.2 Where it is intended to operate the ballast system bypassing the ballast water treatment system (e.g. lifting operations which take in and discharge at the same location before repeating at another location), compliance with Pt 5, Ch 25, 1.1 Application 1.1.3 is required.

5.7.1 Where ballast systems designed for rapid filling/discharge use either piston valves and/or pump ratings without proven service history, the strength of ballast pipe supports and the foundations of the ballast pumps are to be assessed against the forces and moments at the pipe supports and pump flanges for the load combinations defined in Pt 4, Ch 3, 4.3 Load combinations 4.3.1. The permissible stresses are to comply with Table 5.2.1 Factors of safety for the combined load cases.