The reciprocating pump

Auxiliary Engines

Pumps

Aboard vessels several pumping-systems are used, and they are all essential for a smooth running of all activities and proceedings on board the vessel.

General service pumps serve all kinds of purposes. They may, for example, be used for domestic use.

Ballast pumps are used to trim the vessel. A proper trim will enhance safety and reduce fuel consumption. As a rule cargo vessels should not be trimmed down by the head, but must be slightly down by the stern. Listing will occur when there is a difference between draft at port side and draft at starboard side and must be remedied by ballasting the vessel.

Fresh water pumps provide water for cooling-systems.

Fire pumps are used to extinguish fires.

Fuel pumps (high-pressure fuel pumps and booster pumps) supply the fuel for the engine.

Lubricating oil pumps supply the lubricant for the lubrication of engine parts.

Bilge pumps are used to drain superfluous liquids such as fresh and salt water, sweating water, oils, etc. from the holds. These pumps have been fitted with non-return valves that prevent the liquid from flowing back through the lines. Before the mixture of oils and waters is discharged into the mudbox, it is passed through a strainer that filters the substance.

The entire pumping-arrangement on board a vessel must be interconnected, so that in case of a pump- failure in one system pumping can still be continued by other systems. The most common types of pumps are the displacement pumps and the centrifugal pumps. Examples of displacement pumps are the reciprocating pump and the gearwheel pump.

The reciprocating pump

In a reciprocating pump a piston (or plunger) moves up and down and forces the liquid in and out of the pump chamber by creating a vacuum and a pressure force. In a single acting reciprocating pump the liquid is drawn in when the piston goes up, and is forced out when the piston goes down.

In a double-acting reciprocating pump the upward and downward motions of the piston cause simultaneous suction- and discharge actions.

When the piston goes down the lower chamber is emptied through the discharge valve (D2) by pressure. The other discharge valve (D1) is closed by suction. The suction valve (S1) is opened by suction, allowing liquid to enter the upper pump chamber. The other suction valve (S2) is closed by pressure. When the piston goes up, the reverse process will take place.

Double-acting displacement pump

The gearwheel pump

In a gearwheel pump the liquid (fuel oils and lubricating oil) enters through the suction side.

The liquid is then captured between the teeth of the gearwheels (cogs) and is carried around towards the discharge side.

Gearwheel pump