Filter & Strainer on Ship
Filter is a fine mesh screen which is used to remove impurities from oil, water and air on ship. Filters are mounted in pairs as a duplex system so that one can be used and other is kept on stand by at a time. Filter can be used both in low pressure (suction) and discharge (high pressure) side of the system and is used to remove the smallest part of dirt which is carried away in the system. The cleaning frequency of filters depends upon the type of the filter and is decided by the manufacturer. The schedule is normally included in the planned maintenance system on board.
Strainer is a type of filter used mostly on low pressure or suction side and is used to remove large contamination particles from the system. This is because the mesh screen openings in the strainer are bigger in size and are similar to those of coarse filter. If the suction condition is critical, then the strainer can be fitted on the discharge side. This purely depends upon the make and recommendation of the manufacturer. Normally strainers are cleaned whenever they are opened or when the pressure drop on the filter side is high.
Type of Filters Used on Ship
Types of filters depending upon the Media
1) Hydraulic Filter: Hydraulic filters are very useful for removing solid contamination from lube and fuel oil systems of marine machinery. Without filters in the lube or fuel oil system, the machinery internal parts, bearings, rings, auxiliary engine fuel oil line & diesel oil line,marine growth preventive system. Normally a strainer is used in the sea chest so that the flow of water in the sea line is always maintained.
b) Fire line suction filter: Fire pump has a suction filter to avoid any solid impurity to come inside the fire line. The filter mesh screen has a moderate opening screen hole for flow of water.
c) Bilge line filter: All the bilge well suctions are provided with a strainer as the well contains the maximum solid contamination. The filter may have a bucket screen or a plate screen to trap solid impurities like rags etc.
d) Fresh water system filter: All the fresh water systems such as drinking water system, sanitary water system, boiler feed water system etc. are incorporated with a line filter in the suction side of the pump.
3) Air Filter: These filters are used on board so that the compressed air supplied to different machinery and systems get pure air for efficient operation of the same. The different application of the air filters are:
a) Control air filter: The control air system or the pneumatic control of the propulsion plant is very critical. It must not contain any moisture for it may block the passages in the system and the main propulsion plant may not start or reverse etc. The control air filter removes the moisture and collects it in a chamber from where it can be drained.
b) Turbocharger filter: air compressor on board. The air is sucked by the compressor through an air filter located in the first stage and is made up of paper and metal mesh.
d) IG system scrubber filter:
