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Engineering ToolBox > Flow Coefficients - Cv - and Flow Factors - Kv - of Straight Through Diaphragm Valves
The table below indicates typical flow coefficients - Cv - and flow factors - Kv - for diaphragm straight through flanged cast iron valves of "Saunders" type.
| Valve Size | Unlined | Rubber Lined | Glass/Plastic Lined | ||||
| DN | Inch | Cv | Kv | Cv | Kv | Cv | Kv |
| 15 | 9 | 7 | 9 | 8 | |||
| 25 | 1 | 38 | 33 | 31 | 26 | 39 | 34 |
| 32 | 1 | 56 | 48 | 46 | 39 | 58 | 50 |
| 40 | 1 | 75 | 65 | 66 | 57 | 79 | 68 |
| 50 | 2 | 128 | 110 | 107 | 92 | 138 | 119 |
| 65 | 2 | 238 | 205 | 195 | 168 | 254 | 219 |
| 80 | 3 | 330 | 284 | 264 | 228 | 342 | 295 |
| 100 | 4 | 588 | 507 | 480 | 414 | 618 | 533 |
| 125 | 5 | 924 | 797 | 720 | 621 | 960 | 828 |
| 150 | 6 | 1 680 | 1 448 | 1 260 | 1 086 | 1 800 | 1 552 |
| 200 | 8 | 2 580 | 2 224 | 2 196 | 1 893 | 2 724 | 2 348 |
| 250 | 10 | 4 020 | 3 466 | 3 420 | 2 948 | 4 296 | 3 703 |
| 300 | 12 | 6 060 | 5 224 | 4 884 | 4 210 | ||
| 350 | 14 | 10 300 | 8 879 | 9 950 | 8 578 | ||
The opening and closing characteristic of the valves are close to positive linear:
This close to linear characteristic make the valves suited for adjustment and balancing operations. In addition the lined versions are able to resist wear and tear and rough environments and processes.