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Pressure Safety valve sizing calculator for blocked outlet of a vapor filled vessel.
The calculated area is the minimum orifice area required to allow the discharge of liquid. The actual orifice area is the next higher available area. Following table presents the standard orifices with their designating letters and corresponding area. For sizing of a PSV on liquid filled vessel, refer to EnggCyclopedia's PSV sizing calculator for blocked liquid outlet.
| Area (cm2) | Designating letter | Valve size (inch) |
| 0.71 | D | 1D2 / 1.5D2 / 1.5D3 |
| 1.26 | E | 1E2 / 1.5E2 / 1.5E3 |
| 1.98 | F | 1.5F2 / 1.5F3 |
| 3.25 | G | 1.5G3 / 2G3 |
| 5.06 | H | 1.5H3 / 2H3 |
| 8.3 | J | 2J3 / 3J4 |
| 11.86 | K | 3K4 / 3K6 |
| 18.49 | L | 3L4 / 4L6 |
| 23.2 | M | 4M6 |
| 28 | N | 4N6 |
| 41.2 | P | 4P6 |
| 71.2 | Q | 6Q8 |
| 103 | R | 6R8 / 6R10 |
| 168 | T | 8T10 |