Lesson 1. Auxiliary and Deck Machinery

AUXILIARY MACHINERY AND DECK MACHINERY

Machinery other than the main propulsion unit is usually called auxiliary. These include the following: air compressors, heat exchangers, distillation equipment, oil/ bilge water separators, sewage treatment plants and incinerators.

Compressed air has many uses on board ship ranging from diesel engine starting to the cleaning of machinery during maintenance. The air pressures of 25 bar are usually provided in multi-stage machines. Here the air is compressed in the first stage, cooled and compressed to a higher pressure in the next stage and so on. The most common is two stage crank machine.

Heat exchangers on board a ship are mainly coolers where a hot liquid is cooled by sea water. There are some instances where liquid heating is required, such as heavy fuel oil heaters and sea water heaters for tank cleaning. Marine heat exchangers usually have the two liquids flowing in opposite directions, i.e. counter or contra flow, which provides a fairly constant temperature difference between the two liquids and therefore the maximum heat transfer. Coolers at sea fall into 2 groups: the shell and tube and the plate type.

Distillation is the production of pure water from sea water by evaporation and recondensing. Distilled water is produced either by a boiling or a flash process. Oily water separators are used for separation of oil from water. Anti-pollution regulations are becoming more and more stringent so different filters are used to provide the required purity of discharge water.

To meet certain standards introduced by International legislation all new ships have sewage treatment plants installed. There are two particular types of sewage treatment plants using either chemical or biological methods. To achieve the ultimate situation of no discharge a suitable incinerator is used in conjunction with a sewage plant and with facilities for burning oil sludges thus forming a complete waste disposal package.

Deck machinery includes mooring equipment, anchor handling equipment, cargo handling equipment and hatch covers. Other items include life-boats and life-rafts, emergency equipment, watertight doors and bow thrusters. Three forms of power are currently in use for driving deck machinery: steam, hydraulic and electric. All deck machinery is exposed to heavy weather. Total enclosure of all working parts is usual with splash lubrication for gearing. The various bearings on the shafts must be greased by pressure grease points.