hydraulic size
The hydraulic size of a filter media can be calculated directly
from the sieve analysis. The result gives an averaged area size
and is used in the Carman and Kozeny equations to calculate
media flow and backwash expansion.
The calculation of hydraulic size is best illustrated by an example
| Material | Anthracite Filter Media | |
| Grade | 2 [1.18 - 2.50mm] | |
| Sample | 100 grams | |
| Sieve [mm] | Retained % | Retained/Sieve |
| 2.50 | 3.1 | 1.24 |
| 2.00 | 20.4 | 10.20 |
| 1.70 | 29.6 | 17.47 |
| 1.40 | 30.1 | 21.50 |
| 1.18 | 13.8 | 11.69 |
| Tray [0.80] | 3.0 | 3.75 |
| Totals | 100 | 65.85 |
| Divide by 100 | . | 0.66 |
| Reciprocal | . | 1.52 |
| Add 10% | . | 1.67 |
| Hydraulic Size | . | 1.67 mm |