Hydraulic Filters & Hydraulic Filter Accessories

How to Choose the Right Hydraulic Filter

Determine the required filtration level first, match the filter location to the circuit function second, and verify flow capacity and bypass settings before specifying the final housing and element.

• Determine the Required Filtration Level (Micron Rating) Filtration requirements are driven by the most sensitive component in the circuit. Servo valves and proportional valves typically require ISO cleanliness levels of 16/14/11 or better, demanding 3–6 micron filtration. Standard directional valves and cylinders may tolerate 15–25 micron filtration at ISO 18/16/13. Always design filtration to meet the most sensitive component’s requirement — not the average — and verify using a beta ratio rating (β) rather than nominal micron rating alone.
• Match Filter Location to Circuit Function Suction strainers protect the pump at the reservoir outlet but must be sized generously to avoid inlet restriction and cavitation. Return line filters capture system-generated contamination before it re-enters the reservoir and are the most common specification for general hydraulic systems. High-pressure filters downstream of the pump protect precision components in servo and proportional circuits. Offline filter carts supplement the main filtration system for oil conditioning and cleanup without interrupting machine operation.
• Verify Flow Capacity and Bypass Settings A filter sized below the circuit’s peak return flow will open its bypass valve continuously, bypassing unfiltered fluid back to the reservoir and defeating the purpose of the filter entirely. Size the filter housing for maximum flow with adequate margin, and confirm the bypass valve cracking pressure does not interfere with normal back-pressure in the return line. A clogged-filter indicator — visual or electrical — is strongly recommended to prevent operating on a full-bypass condition undetected.