Core Functions and Working Principle

Bilge water inevitably contains contaminants such as cotton waste, fabric scraps, oily sludge, sediment, and various solid impurities. If this debris enters the suction piping directly, it can cause pump impeller jams and pipe blockages; in severe cases, the entire bilge system could fail, compromising vessel safety.

The marine strum box functions by utilizing a perforated screen structure at the suction pipe inlet to trap solid debris at the source, ensuring that only relatively clean bilge water enters the pumping system. Its operating principle is simple and reliable: water flows through the perforations into the suction pipe, while debris is blocked on the exterior of the screen.

Structure and Materials

In accordance with international standard ISO 6454 and various national marine standards, strum boxes typically feature a perforated housing design with the following characteristics:

Housing Shape:  Available in two main categories:  (Type R) and rectangular (Type S).

Perforation Design: Perforated plates are utilized on the sides and/or top of the housing.

Flow Area: The ratio of the total perforation area to the suction pipe's cross-sectional area is typically at least 2:1 (with some models exceeding 3:1) to ensure adequate flow capacity.

Removable Design: The design allows for the cleaning of the box's interior without disconnecting the suction pipe joint.

Common Materials

Carbon steel, brass or stainless steel.

Installation and Maintenance

The strum box is installed at the intake end of the bilge suction pipe and is directly submerged in the bilge water. It should be positioned as close as possible to the lowest point of the bilge, while also ensuring accessibility for crew members to perform regular inspections and cleaning.

Maintenance Points

Periodically open the strainer box to remove accumulated debris.

Check the strainer mesh for blockages or damage.

Avoid damaging the strainer structure during cleaning.

Applications

Intake ends of bilge suction pipes in dry cargo holds, deep tanks, etc.

Bilge water systems on inland and ocean-going vessels.

Used in conjunction with bilge pumps, fire pumps, etc.