In addition to standard strainers, there are several other options available.
A magnetic insert may be placed in a basket type strainer in order to remove small iron or steel debris. Small particles of iron or steel may be present in a fluid where there is wear of iron or steel parts. These particles will pass through even the finest mesh screens, and it is necessary to use a magnetic insert. The insert is designed so that all the fluid passes over the magnet at relatively low velocity and the magnetic element is powerful enough to catch and hold all the metal particles present. The magnetic material is usually encased in an inert material such as stainless steel to prevent corrosion.
There are number of different types of self-cleaning strainer, which enable the build up of debris on the screen to be removed without shutting down the plant. The cleaning process can be initiated either manually or automatically; furthermore, strainers that are automatically cleaned can usually be set to clean either on a periodic basis, or when the pressure drop across the strainer increases.
Mechanical type self-cleaning strainers use some form of mechanical scraper or brush, which is raked over the screen surface. It dislodges any debris that is trapped in the screen, causing it to fall down into a collection area at the bottom of the strainer.
Backwashing type strainers reverse the direction of flow through the screen. A set of valves is changed over so that water is directed across the screen in the reverse direction and out through a flush valve. The fluid dislodges any debris entrained in the screen and carries it out in the backwash fluid to a waste drain.