Different Types of Filters and Strainers on a Ship

As ships spend prolonged periods exploring charted and uncharted waters, it is crucial that both their internal and external structures are properly maintained. Making sure that the frames, cargo holds, propellers, and other structures are in optimal working condition ensures that you will not have to shorten your journey due to improper maintenance or impurities entering your systems. Such impurities can be prevented from entering through the use of filters and strainers. With this in mind, this blog will be covering different types of filters and strainers as well as their applications.

Filters are composed of a fine mesh screen that removes impurities from oil, water, and air aboard the ship. The filters are positioned in pairs as a duplex system so that while one filter is being used, the other is on standby. The filter can be utilized in both the low pressure (suction) and high pressure (discharge) sides of the system to sift out even the most microscopic contaminants. There are various types of filters available for such systems that are distinguished by their cleaning frequency.

A strainer is a type of filter that is used in the suction side of the system and is tasked with removing larger pollutants. The mesh screen contains bigger openings to allow those larger particles to filter out. Strainers are typically cleaned whenever they are opened up or when there is a high pressure drop on the filter side. The next section will give a brief overview of the most commonly used filters on a ship.

Hydraulic Filters

Hydraulic filters remove solid contaminants from the lube and fuel oil systems of a ship. Without such filters, the inner workings of the ship like the bearings, rings, and liners can get damaged. Different applications of hydraulic filters are as follows:

Fine Mesh Screen Filter

This type of filter can be used on both the suction and discharge side of the system. Moreover, it is implemented in the cylinder lube oil line, main engine & auxiliary engine fuel oil line, diesel oil line, boiler fuel oil line, and in different lube oil systems onboard.

Magnetic Filter

This filter consists of magnetic filter elements that help catch granular metals as they make their way into the system. These elements are surrounded by a basket screen that acts as a filter which simplifies the cleaning process.

Auto Backwash Filter

In auto backwash filters, you are alerted that the filter is clogged when the pressure difference increases. The auto system responds by cutting off the filter and opening the bypass. In this system, an electric motor connected to a shaft cleans the filter, and the drain of the filter opens up.

Centrifugal Filter

These filters work by using centrifugal force to remove high-density fluids and impurities from oil. They are typically found in the auxiliary engines.

Manual Clean Filter

Manual clean filters have a handle with a shaft that is connected to the inside of a filter. As the pressure difference increases, the filter unit is bypassed, and a lever aids in the manual cleaning of the filter.

Water Filters

The sea water and fresh water systems on a ship usually have line filters that prevent solid impurities from making their way into the system. The sea water side has more filters and the fresh water systems are closed so they require less filtration components. The next group of filters are all categorized as different types and applications of water filters.

Sea Chest Strainer

This kind of strainer is inserted in the main suction line of the sea water inlet system. The filter casing is generally fitted with the marine growth prevention system (MGPS).

Fire Line Suction Filter

The fire pump contains a suction filter to prevent any solid pollutants from going inside the fire line. Moreover, the filter mesh screen has moderately-sized openings to facilitate the flow of water.

Bilge Line Filter

Bilge well suctions are provided with a strainer while the well contains a majority of the solid contamination. Additionally, the filter may be equipped with a bucket or plate screen to trap solid impurities.

Fresh Water System Filter

This type of filter contains a line filter on the suction side of the pump.

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