The 25P is a self-acting pilot-operated pressure reducing valve. It senses downstream pressure through an external pressure sensing tube, adjusts the main valve opening, and maintains stable pressure. The valve can be closed when there is no downstream load.
| Constraints (Ductile) | ● Design pressure (PMA): 21 bar ● Maximum operating pressure (PMO): 17.2 bar ● Maximum operating temperature (TMO): 232°C |
| Downstream Pressure Range | Three different colored springs are available to control downstream pressure: ● Yellow: 0.2 bar – 2.1 bar ● Blue: 1.4 bar – 7.0 bar ● Red: 5.6 bar – 14.0 bar |
| Bill of Materials | ● Valve body and cover: QT400-18 ● Main valve seat and pilot valve seat: Martensitic stainless steel ● Main valve disc and pilot valve core: Martensitic stainless steel ● Pressure regulating spring: Silicon-chromium spring steel ● Other internal parts: Stainless steel |
Flow
The table below shows the Cv value when the valve is fully open, which is used for safety valve selection.
Cv value
| Caliber | 1/2″ | 3/4″ | 1″ | 11/4″ | 1/2″ | 2″ | 21/2″ | 3″ | 4″ | 5″ |
| Cv | 3.48 | 6.5 | 10.5 | 14 | 20 | 35 | 56 | 74 | 115 | 123 |
Conversion formula: Cv(US) = Kv x 1.156
Dimensions/weight (approximately) mm and kg
| model | 25P | ||||||||||
| Nominal diameter | 15 | 20 | 25 | 32 | 40 | 50 | 65 | 80 | 100 | 125 | |
| A(mm) | 140 | 152 | 184 | 216 | / | ||||||
| A1(mm) | 160 | 166 | 205 | 216 | 240 | 288 | 316 | 361 | 400 | ||
| B(mm) | 193 | 219 | 269 | 346 | 397 | ||||||
| C(mm) | 309 | 322 | 338 | 297 | 294 | 325 | |||||
| D(mm) | 157 | 171 | 179 | 208 | 354 | 367 | 410 | ||||
| E(mm) | 466 | 479 | 501 | 546 | 651 | 661 | 735 | ||||
| Weight (Kg) | Thread | 11 | 10.5 | 14 | 16.5 | 16 | 26 | / | |||
| Flange | 12 | 12.5 | 16 | 19 | 20.5 | 31.5 | 63 | 75 | 112 | 132 | |
25P pressure reducing valve steam flow diagram
Note: This diagram is for reference only. For critical applications, it is recommended to select the appropriate flow meter based on CV (CV) calculations. The suggested CV value for actual operating conditions should be between 20% and 80% of the valve’s total CV. This flow meter is based on the installation of an external sensing tube. Without an external sensing tube, the flow rate will decrease. Under very low downstream pressure conditions, the flow rate reduction can reach up to 30%.
How to use flow charts
The following two examples of saturated steam and superheated steam will explain how to use this flow chart.
Saturated steam
Flow rate 5000 kg/h, pressure reduced from 8 bar to 5 bar.
Finding the valve diameter that meets the flow requirements by moving vertically downwards from the fulcrum of the upstream pressure of 8 bar and the downstream pressure of 5 bar, an 80 mm valve is found to be the minimum acceptable diameter.
Due to the higher specific volume of superheated steam, the data obtained from the diagram needs to be corrected. The correction factor for superheating at 55°C (100°F) is 0.95, and the correction factor for superheating at 110°C (200°F) is 0.9. Therefore, with an 80 mm valve, if the steam is superheated to 55°C, the flow rate is 5900 × 0.95 = 5600 kg/h, which is still sufficient to meet the required 5000 kg/h.
Optimized by Seraphinite Accelerator
