Perforated plate strainers provide coarse filtration down to about 150 um. For finer filtering, wire mesh elements are normally used in conjunction with perforated plate or other form of reinforcement, when this is necessary for added mechanical strength. Wire mesh strainers can provide filtration down to about 40m, but with reduced strength due to the increasingly fine wire used.
Numerically, the service life of a strainer (between cleaning times) can be expressed in terms of the ratio of open area of the strainer to the pipe cross-section. Open area is determined by the choice of perforation or mesh, which would normally be of the order of 15–20%. Strainers are usually proportioned to provide a 3:1 area ratio for general service, although this may need to be doubled in the case of more viscous fluids.