Suction filters are used in the hydraulics sector to protect hydraulic pumps

In general, hydraulic filters serve to keep the oil as clean as possible. They filter suspended particles and prevent further abrasion in all components.

Suction filters are a special type of these containment systems. They are primarily designed for pump protection. Since they are mounted upstream of the hydraulic pump, the volume flow is sucked through the filter housing. Hence the name. Filters mounted on the pressure side are accordingly called pressure filters.

Design of suction filters

A suction filter is technically simple. It consists of a robust housing with two large screw connections. Inside the housing is a replaceable filter cartridge. To replace it, the hydraulic system must be switched off and cooled down! Only then can the suction filter housing be opened easily and safely. When replacing the filter cartridge, it is advisable to clean the housing thoroughly and replace the seal. The flow direction of the hydraulic stream is marked with an arrow on the filter housing. It is very important to install the filter correctly, otherwise it can quickly generate back pressure.

Design and sizing of suction filters

Suction filters must match the hydraulic system and, above all, the pump used. The greater the contamination in the filter cartridge, the more the vacuum behind the suction filter increases. Even from a pressure difference of 0.2 bar, the formation of dreaded cavitation can occur. These are vacuum bubbles in the hydraulic oil that collapse with high force. The resulting shock waves have a destructive effect on all components of the hydraulic system and especially on the directly affected pump.

The suction filter must therefore be precisely tailored in size and performance to the existing conditions! Furthermore, it is particularly important with this type of filter that the replacement intervals for the filter cartridge are strictly observed.

Additional suction filters in hydraulic systems

Suction filters can also be installed on other components of hydraulic systems, e.g., on the tank. There, suction filters are also called “suction strainers.” The suction strainer must be positioned very precisely. Positioned too close to the surface, it can suck in air and thus endanger the function of the hydraulic system. Positioned too close to the bottom of the tank, the filter can suck in deposits, which clog the cartridge prematurely.

Instead of installing the suction filter in the tank, it can also be mounted externally. This is particularly convenient for maintenance and inspection purposes. In mobile hydraulic systems, such as in construction machinery, the in-tank design is nevertheless preferred. This avoids the risk of the external filter being torn off by machine movements.