## Learn how to figure the ratio of free area to pipe area from Eaton Filtration We are often asked how to figure the ratio of free area to pipe area when a customer changes/requires different perforations or  mesh sizes  in a industrial strainerHere is a simple calculation to do this.

A. With perforated basket( s ), take the gross · screen area of the model and size strainer times the percent open area of the perforation required and divide by 100. This gives the new free area. Divide the new free area by nominal area to get the new ratio of free area to pipe. Ex.: 2″ #72 with 7/64 perf- gross area 50.9 X 46.0 the (% open area of 7/64″) divided by 100 =
23.4. 23.4 divided by 3.35 (nominal area) = ratio free area to pipe of 6.9:1.

B. With mesh basket(s)- the same calculation as for perforated baskets above but use 5/32 perf (standard with mesh lined baskets) having 63.0% open area. After
you get the free area of the perf, multiply it by the open area % of the mesh divided by 1 00 to obtain the free area of perf/mesh combined. Divide this answer by the nominal area of the pipe to get the new  ratio of free area to pipe. Ex.: 2″ #50 with 100 mesh- gross area 64.0 X 63.0 (the % open area of 5/32″ perf) divided by 1 00 = 40.3. 40.3 X 30.3 (% open area of 100
mesh) divided by 100 = 12.2. 12.2 divided by 3.35 (nominal area) = ratio free area to pipe of3.6:1.

After you try it a few times, you will see how really simple it is!

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