Section 7 Chilled water systems

7.1.1 The requirements in this Section are additional to those contained in Vol 2, Pt 7, Ch 5, 2 Construction and installation of this Chapter.

7.1.2 Chilled water systems are to produce and distribute treated demineralised chilled water throughout the ship to provide cooling to heat exchangers and other direct cooled equipment that may include air conditioning and weapons systems.

7.1.3 The refrigeration plant and chilled water system is to be designed to be capable of continuously extracting at least 115% of the maximum heat load duty when operating at the conditions stated in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2.

7.1.4 The demineralised water used in chilled water distribution systems is to be in accordance with the system designer's specification.

7.1.5 Where chilled water is used to provide a controlled environment for equipment and machinery intended for Mobility and/or Ship Type systems which require this controlled environment to function, an alternative means is to be provided to maintain the required environment in the event of a failure of the chilled water system. Failure of the chilled water system is to initiate an alarm. Duplication of the equipment requiring cooling can be provided instead of an alternative means of cooling, providing that the duplicated equipment is fed from an alternative, independent chilled water system.

7.2.1 Two or more independent refrigeration plants are to be provided and designed to be capable of extracting the heat load duty required by Vol 2, Pt 7, Ch 5, 7.1 General 7.1.3 when operating at the conditions stated in the System Design Description with any one plant out of action.

7.2.2 The refrigeration plants are to be located in separate compartments and zones such that the loss of one compartment or zone, or failure in equipment will not render the other refrigeration plant(s) inoperative. In NS3 category ships the requirement for plants to be located in separate zones will not be insisted on where agreed by the Owner and included in the System Design Description.

7.2.3 The refrigeration systems and compartments containing the refrigeration plants are to comply with the requirements in Vol 2, Pt 11, Ch 4 Refrigeration System Arrangements, and are to be provided with refrigerant gas detectors in accordance with Vol 2, Pt 9, Ch 11 Gas detection with audible and visual alarms.

7.3.1 Two or more chilled water pumps are to be provided and be of sufficient capacity to circulate chilled water at the flow rate and conditions stated in the System Design Description with any one pump out of action.

7.3.2 The chilled water pumps are to be located in separate compartments and zones such that loss of one compartment or zone or failure in equipment will not render the chilled water system inoperative.

NOTE:

This does not preclude locating the chilled water pumps in the same compartment as the refrigeration plants mentioned in Vol 2, Pt 7, Ch 5, 7.2 Refrigeration plant. Plants and their associated chilled water pumps are to be arranged such that the pumps can be cross-connected to other plants in the event of plant or pump failure. In NS3 category ships the requirement for pumps to be located in separate zones will not be insisted on where agreed by the Owner and included in the System Design Description.

7.3.3  The chilled water distribution system is to be of the constant flow type with a pneumatically pressurised expansion tank. Expansion tanks are to have a membrane fitted at the air/water interface to prevent ingress of air into the chilled water system.

7.3.4 Each user of chilled water is to be provided with means of isolation such that the distribution system can operate at the designed constant flow rate when the user is isolated.

7.3.5 The arrangement of chilled water distribution pipes and isolation valves is to ensure continuous availability of supply in the event of the loss of any one compartment or zone.

7.3.6  Air vent and drain valves with adequate bleed off points for filling and in-service operational requirements are to be provided throughout the system at all high and low points.

7.3.7 Provision is to be made for filling and topping up the chilled water system. A means is also to be provided for connecting the system to a dry main for shore connection above the waterline. The shore connection is to be sized sufficient to enable supply of cooling water for the ship’s requirement as declared in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2.

7.3.8 Provision is to be made to connect the chilled water distribution system to an alternative source of water supply for use in emergency/action damage conditions.

7.3.9 Sea-water systems for refrigeration condensers are to be capable of being supplied from not less than two independent sources located in separate compartments and zones such that the loss of one compartment or zone, or failure in equipment will not render loss of all sea-water sources. In NS3 category ships the requirement for refrigeration condensers to be located in separate zones will not be insisted on where agreed by the Owner and included in the System Design Description.

7.3.10 The capacity of each source of sea-water required by Vol 2, Pt 7, Ch 5, 7.3 Water system 7.3.9 is to be sufficient for the conditions stated in the System Design Description with any one source out of action.