Suction Filters - Clean the hydraulic medium pumped out of the tank by the pump

The main function of a hydraulic filter is to remove contaminants and particles from the hydraulic fluid. Around 80% of premature hydraulic system failures are caused by contaminated hydraulic fluid. Hydraulic filters significantly help extend component service life, maintain operating efficiency and prevent unexpected downtime.

• Internal contamination: Caused by component wear, rubber particles from hoses or ageing residues of the fluid, intensified by high temperatures.
• External contamination: Enters the system during assembly work, through leaking tanks or inadequate air filters. Some contamination also comes from insufficient tank breather filters.

• Surface filters: Thin mesh (e.g. metal, cellulose, plastic, paper), often pleated to increase the area. Traps particles on the surface. Typical ratings: 25, 60, 90 µm.
• Depth filters: The fluid passes through a porous structure (e.g. cellulose, fibreglass, sintered metal). Particles are retained in deeper layers. Microfibre fleece allows filtration down to 1 µm. Paper filters offer an economical solution (10–25 µm).

A suction filter is a protective filter installed directly before the hydraulic pump. It retains coarse contaminants before they reach the pump and prevents damage. To avoid cavitation, a rather coarse filtration rating (> 25 µm) is used. Suction filters often operate in combination with finer system filters.

• Return filters: Most commonly used, installed directly on the tank or in the return line. Cost-effective, easy to maintain and suitable for fine filtration. Require a bypass valve.
• Pressure filters: Installed after the pump in the pressure line. Protect sensitive components (e.g. proportional valves). Allow very fine filtration, robust, more expensive.
• Tank breather filters: Installed on the filling or breather port. Prevent dirt from entering the tank through the air.

• Pump protection: Against coarse contaminants and tank particles.
• Longer service life: Prevents damage and increases system reliability.
• Easy maintenance: Filter elements can be cleaned or replaced easily.
• High dirt-holding capacity: Efficient design with low differential pressure.
• Low risk of cavitation: Due to coarse filtration (usually > 25 µm), keeping flow resistance low.

• Flow rate: Dimensioned according to maximum flow (e.g. up to 400 l/min).
• Filtration rating: Typically coarse (> 25 µm) to avoid cavitation.
• Hydraulic oil: Filter material must be compatible.
• Load capacity: Housing and element must withstand pressure and temperature conditions.
• Size & installation location: Depending on space and whether tank-mounted or in-tank installation.
• Manufacturer specifications: Observe differential pressure and system compatibility requirements.

Suction filters are easy to maintain. The filter element can be removed, cleaned or replaced. Often washing out is sufficient, but in cases of heavy contamination or damage, replacement is necessary. Maintenance intervals depend on operating conditions and contamination levels. Regular inspection and cleaning significantly extend service life and ensure reliable system protection.