Strainers:

Strainers are fitted in several piping lines to avoid the passage of scale, grit, dirt, and other foreign matter, that could throttle valves, obstruct pump suction valves, or other machinery elements. One of the easiest and most general categories of strainers found in piping systems is the Y-strainer that is described in Figure.

Figure: Y-strainer

Above figure describes three further general categories of strainers.