Section 8 High pressure compressed air systems

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

8.1.2 High pressure (HP) compressed air systems are to produce and distribute compressed air throughout the ship to supply all systems and equipment where the air pressure requirement exceeds 7 bar. The systems are to include air compressors, oil/water separators, filter/dryers, distribution lines and air receivers. For the purpose of maintenance and safety regulatory requirements, HP air systems may be defined as those where the air pressure requirements exceed 25–40 bar and this is to be defined in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2.

8.1.3 The requirements for HP compressed air systems include the storage and distribution of compressed air with air pressures above 7 bar and are to be in accordance with the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2. Additional compressed air systems may be installed for specific purposes such as for engine starting (typically 25–30 bar systems) which are also to comply with the requirements of this Section and Vol 2, Pt 7, Ch 3, 12 Air compressors and air starting arrangements as applicable.

8.1.4 The design of HP compressed air systems is to be capable of providing continuous flow for all demands of equipment and system consumers, recognising continuous and intermittent users. This includes any portable equipment that may be part of the ship's equipment.

8.1.5 The compressed air system users' quality (dryness, purity, etc.) requirements of compressed air are to be recognised in the selection of compressors, equipment, filters and dryers to be included in the system(s).

8.1.6 Arrangements for emergency depressurisation of HP compressed air to safe positions on open deck are to be provided. The controls for emergency depressurisation are to be located in readily accessible positions outside the space containing the HP air receivers.

8.2.1 Two or more HP air compressors are to be provided of sufficient capacity to supply the total design demand of the system under defined requirements stated in the System Design Description required by Vol 2, Pt 7, Ch 5, 1.3 Documentation required for design review 1.3.2 with any one compressor out of action.

8.2.2 The compressors 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 compressor(s) inoperative.

8.2.3 Each compressor is to be fitted with a safety valve so proportioned and adjusted that the accumulation of pressure with the outlet valve closed will not exceed 10 per cent of the maximum working pressure of the compressor. The casings of the cooling water spaces are to be fitted with a safety valve or bursting disc so that ample relief will be provided in the event of the bursting of an air cooler tube.

8.2.4 Each compressor is to be provided with an alarm for failure of the lubricating oil supply that will initiate an automatic shutdown.

8.2.5 Adequate air supply arrangements via a steel trunk are to be provided to the compartment where the compressor is located and where a vessel is provided with an CBRN citadel, arrangements are to ensure that there is adequate air supply to the compressor in closedown. Care is to be taken to ensure that the compressor air inlets will be located in an atmosphere reasonably free from oil vapour..

8.2.6 Provision is to be made for intercepting and draining oil and water in the air discharge for which purpose a separator or filter is to be fitted in the discharge pipe from each compressor.

8.2.7 Drain valves for removing accumulations of oil and water are to be fitted on compressors and their associated coolers, separators and filters.

8.3.1 The HP air system and associated air receivers are to be configured to provide sufficient capacity to supply HP compressed air to users when any section of the distribution line is isolated due to failure or damage.

8.3.2 The configuration of the HP air system and associated air receivers for each essential user of HP compressed air is to be arranged to provide without replenishment, sufficient air to operate systems and equipment at an agreed capability level for an agreed period of time. In general, at least two air receivers of approximately equal capacity are to be provided for each essential user or group of users.

8.3.3 All air receivers are to be provided with mounting and fittings required by Vol 2, Pt 8, Ch 2, 9 Mountings and fittings.

8.3.4 Stop valves on air receivers are to permit slow opening to avoid sudden pressure rises in the piping system.

8.3.5 Air receivers used for pressurising magazine water spray systems are to be capable of being isolated from the HP compressed air distribution lines to prevent automatic replenishment of the receiver after use.

8.4.1 The arrangement of HP compressed air pipes and isolation valves is to ensure continuous availability of supply in the event of the loss of any one compartment or zone. Isolating valves are to be fitted in each branch from the main distribution system to permit isolation of any damaged branches.

8.4.2 Drain pots with drain valves are to be provided throughout the distribution system at all low points.

8.4.3 Reducing valves/stations for users of reduced pressure air are to be provided throughout the ship. Pipelines that are situated on the low pressure side of reducing valves/stations, and that are not designed to withstand the full pressure of the source supply, are to be provided with pressure gauges and with relief valves having sufficient capacity to protect the piping against excessive pressure. Inline filters are to be fitted at each reducing valve/station on the high pressure side.

8.4.4 A means is to be provided for connecting the HP compressed air system to a shore connection.