A hydraulic circuit usually has filtration in two places: at the pump inlet and on the return line to the tank. The two elements are not interchangeable, and the reason is pressure drop.
The suction side
A suction strainer sits between the tank and the pump inlet. Its job is to stop large debris — swarf, seal fragments, sand from a badly cleaned reservoir — from reaching the pump. Because it is on the suction side, any pressure drop it creates adds directly to the risk of cavitation. That is why suction elements are coarse: our WU and TFX strainers are rated 80–180 µm and are used at working pressures up to 0.6 MPa.
Suction filters are normally mounted on the side, top or bottom of the tank, with a self-sealing valve so the element can be withdrawn without draining the reservoir, and a bypass valve so a blocked strainer does not starve the pump.
The return side
A return-line filter is where the fine filtration happens. It sees flow at low pressure after the work is done, so it can afford a much finer rating: our return elements are available from 1 µm to 25 µm at β ≥ 100, with structural strength from 1.0 MPa to 21.0 MPa. The housing sits on the tank top and carries a diffuser to avoid foaming, a bypass valve, and a clogging indicator so the element is changed on condition rather than on a schedule.
The practical rule
- Coarse and large-area on the suction side, to protect the pump from cavitation.
- Fine and high β-ratio on the return side, to protect the valves and actuators.
- Never fit a fine element in a suction housing to “improve cleanliness” — you will destroy the pump.
- Change both on differential pressure, and check the indicator is actually working.
Matching an existing machine
Send the model number of the element you are replacing. Suction and return elements are dimensionally different — different diameters, different end caps and different sealing faces — and our interchange check confirms which family a reference belongs to before quoting.