Suction filters are categorised into Strainers/Suction Elements, Spin-On Filters and Tank-Wall Mounted Filters.
Suction elements/strainers are widely used as they are cost effective & are housed within the reservoir thus reducing the need for any external work. They are typically made with a 125 micron wire mesh media to remove large particle that may find their way into the tank & protect the pump.
The negative aspect of strainers is that they have no indicator or bypass & because they are inside the tank it is not possible to know when they need changing. A strainer that is left indefinitely will ultimately become so blocked that it will reduce the oil flow to such an extent that it causes cavitation of the pump.
Spin-on filter – see above but amend flow rates to 80 l/min.
Tank-wall mounted filters such as the MP Filtri SF2 series are designed with a built-in valve that can be closed by use of a handwheel to enable a change of the element without emptying the reservoir. Elements are typically available with 25-250 micron ratings.