Air and pumping
- The compressed-air system: the compressors, the air receivers with their safety valves and drains, and the starting-air supply.
- Pumps and pumping: centrifugal and positive-displacement pumps and where each is used.
- The bilge system: the bilge wells, the pumps, the oily-water separator and the bilge alarms.
- The ballast, fresh-water and general-service systems.
Compressed air starts many engines and drives controls, and the air receivers store large energy under pressure, so their safety valves, drains and survey requirements are respected. The bilge system removes water from the lowest parts of the vessel, and its oily-water separator ensures any water discharged overboard meets the legal oil limit. A bilge alarm is a warning of water ingress that the watchkeeper investigates at once.
WARNING — Air receivers store dangerous energy An air receiver holds a large amount of energy under pressure. Respect its safety valves and drains, drain the condensate regularly, and never tamper with its pressure settings or survey requirements.
NOTE — The oily-water separator keeps the discharge legal Bilge water is passed through the oily-water separator so that any water discharged overboard is below the legal oil content. Discharging oily bilge water directly overboard is illegal.