Suction Strainer
The suction strainer sits at the pump inlet and is the coarse filter that keeps large particles out of the pump. Its rating is typically 100-150 micron; using a finer element raises suction resistance and leads to cavitation. Its clogging is a classic cause of pump failures.
On the suction side the pump does not push the oil, it draws it with atmospheric pressure. That is why every resistance in the suction line translates directly into cavitation risk. As the strainer gets dirty, pressure at the pump inlet drops, air in the oil separates out as bubbles, and the bubbles collapse on the discharge side, hammering the metal surface.
- Diagnosis by sound: a scraping pump noise resembling gravel is the first sign.
- Cold starting: suction resistance rises while viscosity is high; in winter strainer clogging shows itself earlier.
- Maintenance: it sits inside the tank and is often forgotten; it must be cleaned at every oil change.
When a spongy and irregular lever feel is reported, this component should be near the top of the checklist. Making the control electronic does not fix the shaky motion caused by aerated oil coming from the suction side; the problem is not on the control side but in the fluid itself.
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