pump

pump, an essential piece of mechanism on board ship, used for emptying the bilges of any water which may have collected in them. Three types of pumps were fitted in the old sailing vessels to clear the bilges. A small hand-pump, similar to those used ashore, was placed near the mainmast, used when there was only very little water in the bilge and a short spell of pumping would clear it. It was a slow and laborious method. Some ships, particularly Dutch and German ones, used a burr-pump, also known as a bilge pump, in which a spar of wood about 1.8 metres (6 ft) long had a burred end to which a leather was fixed. Two men standing over the pump thrust this down into the box in which the bilge water collected, and six men then hauled it up by a rope fixed to it, thus lifting the water which lay on top of the leather. The third type was the chain-pump, which worked on a similar system to the burr-pump but with an endless motion so that there was no need for men to thrust it down in the bilge-box on each stroke. This was a most efficient pump, and two men working on it could lift a ton of water in 55 seconds. According to Sir Walter Raleigh, it was one of the improvements—bonnets, studsails, anchor capstans, and the ability to strike down a ship's topmast being the others—introduced into the British Navy during his time.

Modern pumps in ships are power driven and are capable of lifting some hundreds of tonnes of water an hour. Most smaller yachts have hand-operated diaphragm pumps which are more efficient than the plunger type. In steamships and their modern equivalents there are many other types of pump, used in connection with their internal machinery, such as fuel pumps to feed the boilers, circulating pumps to draw in seawater for the condensers, feed pumps to return condensed steam to the boilers, trimming pumps to transfer water ballast from one tank to another, and so on.

See also rose box.