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The AH42F safety reflux valve is a composite valve that integrates safety relief and medium reflux functions. It is typically installed at the outlet of a pump or on pipelines requiring pressure protection. When the pipeline pressure exceeds the set safety value, the valve opens as a safety valve to relieve pressure. When the pump suddenly stops or the downstream pressure is higher than the upstream pressure, the valve can act as a check valve to allow limited reflux of the medium, preventing water hammer, system backflow, and pump reversal. The "F" in the valve model indicates that the valve seat sealing surface is directly machined from the valve body material. This valve simplifies pipeline design and provides integrated safety protection and hydraulic control for pumps and pressure systems. It is mainly installed in the outlet pipelines of centrifugal pumps, water supply systems, fire pump sets, irrigation systems, and industrial circulating water systems. It is used to prevent system overpressure, avoid the hazards of water hammer during pump shutdown, and prevent damage to the pump caused by medium backflow. It is a commonly used multifunctional protection valve in pump pipelines.
AQ-20 Air Compressor Safety Valve Product Diagram
Features:
1. Dual function of safety pressure relief and backflow
Integrate the functions of a safety valve and a check valve into a single valve body. The system is protected by releasing pressure in case of overpressure; it allows controlled backflow when the pump stops or the backpressure is too high, preventing water hammer and pump reversal.
2. Valve body sealing surface (Type "F")
The sealing surface is directly machined or built up by welding from the valve body material, which is economical and durable, suitable for non-corrosive media such as water and oil.
3. Spring-loaded, reliable action
The spring direct load mechanism is adopted to provide stable opening pressure and return opening pressure, ensuring sensitive and reliable action.
4. Compact structure, simplified piping
One valve serves two functions, reducing the number of valves required on the pipeline, saving installation space and costs, and simplifying the system.
5. Easy to maintain
The structure is relatively simple, with fewer wearing parts, making maintenance and inspection more convenient.

AQ-20 Air Compressor Safety Valve Structural Diagram
Part Name Material
| 阀体、阀盖 body\cover | WCB |
| 阀座、阀瓣、阀杆 seat\dic\stem | 铬不锈钢Chromium stainless stee |
| 弹簧 spring | 铬钒钢Chromium Vanadium Steel |
| 密封面sealing surface | 聚四氟乙烯PTFE |
Performance Specifications Table
| 公称压力nominal pressure | 壳体试验Shell Test | 密封试验Sealing Test | 开启压力opening pressure | 适用介质Application medium | 适宜温度Applicationtemperature |
| 1.6 | 2.4 | 0.9PK | 用户确定User confirmed | 液化气、天然气等非腐蚀性介质Non-corrosive media such as liquefied gas and natural gas | -40~+80℃ |
| 2.5 | 3.75 | ||||
| 4.0 | 4.4 |

AQ-20 Air Compressor Safety Valve Outline Drawing
Dimension Chart
| 型号model | 公称通径Nominal diameter | do | D | K | g | g1 | b | f | f1 | Z-ød | DN’ | D1 | K1 | g2 | b1 | f’ | Z1-ød1 | L | L1 | ≈H |
| AH42F-16C A42F-16C | 20 | 15 | 105 | 75 | / | 55 | 16 | 2 | / | 4-14 | 25 | 115 | 85 | 65 | 16 | 2 | 4-14 | 110 | 95 | 378 |
| 25 | 16 | 115 | 85 | / | 65 | 16 | 2 | / | 4-14 | 32 | 140 | 100 | 78 | 18 | 2 | 4-18 | 110 | 95 | 378 | |
| 32 | 20 | 140 | 100 | / | 78 | 18 | 2 | / | 4-18 | 40 | 150 | 110 | 85 | 18 | 3 | 4-18 | 115 | 100 | 378 | |
| 40 | 25 | 150 | 110 | / | 85 | 18 | 3 | / | 4-18 | 50 | 165 | 125 | 100 | 20 | 3 | 4-18 | 120 | 110 | 406 | |
| 50 | 32 | 165 | 125 | / | 100 | 20 | 3 | / | 4-18 | 65 | 185 | 145 | 120 | 20 | 3 | 4-18 | 135 | 120 | 450 | |
| 65 | 40 | 185 | 145 | / | 120 | 20 | 3 | / | 4-18 | 80 | 200 | 160 | 135 | 20 | 3 | 8-18 | 160 | 140 | 520 | |
| 80 | 50 | 200 | 160 | / | 135 | 20 | 3 | / | 8-18 | 100 | 220 | 180 | 155 | 22 | 3 | 8-18 | 170 | 135 | 525 | |
| 100 | 65 | 220 | 180 | / | 155 | 22 | 3 | / | 8-18 | 125 | 250 | 210 | 185 | 22 | 3 | 8-18 | 195 | 175 | 690 | |
| 125 | 80 | 250 | 210 | / | 185 | 22 | 3 | / | 8-18 | 150 | 285 | 240 | 210 | 24 | 3 | 8-23 | 210 | 190 | 780 | |
| 150 | 100 | 285 | 240 | / | 210 | 24 | 3 | / | 8-23 | 175 | 310 | 270 | 240 | 26 | 3 | 8-23 | 255 | 230 | 838 | |
| 200 | 125 | 340 | 295 | / | 265 | 26 | 3 | / | 12-23 | 250 | 405 | 355 | 320 | 30 | 3 | 12-26 | 300 | 260 | 992 | |
| 250 | 150 | 405 | 355 | / | 320 | 30 | 3 | / | 12-26 | 300 | 460 | 410 | 375 | 30 | 4 | 12-26 | 350 | 320 | 1266 | |
| 300 | 220 | 460 | 410 | / | 375 | 30 | 4 | / | 12-26 | 400 | 580 | 525 | 485 | 36 | 4 | 16-30 | 370 | 350 | 1283 |
| 350 | 250 | 520 | 470 | / | 435 | 34 | 4 | / | 16-26 | 500 | 715 | 650 | 608 | 44 | 4 | 20-34 | 500 | 450 | 1520 | |
| 400 | 280 | 580 | 525 | / | 485 | 36 | 4 | / | 16-30 | 500 | 715 | 650 | 608 | 44 | 4 | 20-34 | 500 | 450 | 1530 | |
| AH42F-25 A42F-25 | 20 | 15 | 105 | 75 | / | 55 | 16 | 2 | / | 4-14 | 25 | 115 | 85 | 65 | 16 | 2 | 4-14 | 110 | 95 | 378 |
| 25 | 16 | 115 | 85 | / | 65 | 16 | 2 | / | 4-14 | 32 | 140 | 100 | 78 | 18 | 2 | 4-18 | 110 | 95 | 378 | |
| 32 | 20 | 140 | 100 | / | 78 | 18 | 2 | / | 4-18 | 40 | 150 | 110 | 85 | 18 | 3 | 4-18 | 115 | 100 | 378 | |
| 40 | 25 | 150 | 110 | / | 85 | 18 | 3 | / | 4-18 | 50 | 165 | 125 | 100 | 20 | 3 | 4-18 | 120 | 110 | 406 | |
| 50 | 32 | 165 | 125 | / | 100 | 20 | 3 | / | 4-18 | 65 | 185 | 145 | 120 | 20 | 3 | 4-18 | 135 | 120 | 450 | |
| 65 | 40 | 185 | 145 | / | 120 | 22 | 3 | / | 8-18 | 80 | 200 | 160 | 135 | 20 | 3 | 8-18 | 160 | 140 | 520 | |
| 80 | 50 | 200 | 160 | / | 135 | 22 | 3 | / | 8-18 | 100 | 220 | 180 | 155 | 22 | 3 | 8-18 | 170 | 135 | 525 | |
| 100 | 65 | 230 | 190 | / | 160 | 24 | 3 | / | 8-23 | 125 | 250 | 210 | 185 | 22 | 3 | 8-18 | 195 | 175 | 690 | |
| 125 | 80 | 270 | 220 | / | 188 | 28 | 3 | / | 8-26 | 150 | 285 | 240 | 210 | 24 | 3 | 8-23 | 210 | 190 | 780 | |
| 150 | 100 | 300 | 250 | / | 218 | 30 | 3 | / | 8-26 | 175 | 310 | 270 | 240 | 26 | 3 | 8-23 | 255 | 230 | 838 | |
| 200 | 125 | 360 | 310 | / | 278 | 34 | 3 | / | 12-26 | 250 | 405 | 355 | 320 | 30 | 3 | 12-26 | 300 | 260 | 992 | |
| 250 | 150 | 425 | 370 | / | 332 | 36 | 3 | / | 12-30 | 300 | 460 | 410 | 375 | 30 | 4 | 12-26 | 350 | 320 | 1266 |
| AH42F-40 A42F-40 | 300 | 220 | 485 | 430 | / | 390 | 40 | 4 | / | 16-30 | 400 | 580 | 525 | 485 | 36 | 4 | 16-30 | 370 | 350 | 1283 |
| 20 | 15 | 105 | 25 | 51 | 55 | 16 | 2 | 4 | 4-14 | 25 | 115 | 85 | 65 | 16 | 2 | 4-14 | 110 | 95 | 378 | |
| 25 | 16 | 115 | 85 | 58 | 65 | 16 | 2 | 4 | 4-14 | 32 | 140 | 100 | 78 | 18 | 2 | 4-18 | 110 | 95 | 378 | |
| 32 | 20 | 140 | 100 | 66 | 78 | 18 | 2 | 4 | 4-18 | 40 | 150 | 110 | 85 | 18 | 3 | 4-18 | 115 | 100 | 378 | |
| 40 | 25 | 150 | 110 | 76 | 85 | 18 | 3 | 4 | 4-18 | 50 | 165 | 125 | 100 | 20 | 3 | 4-18 | 120 | 110 | 406 | |
| 50 | 32 | 165 | 125 | 88 | 100 | 20 | 3 | 4 | 4-18 | 65 | 185 | 145 | 120 | 20 | 3 | 4-18 | 135 | 120 | 450 | |
| 65 | 40 | 185 | 145 | 110 | 120 | 22 | 3 | 4 | 8-18 | 80 | 200 | 160 | 135 | 20 | 3 | 8-18 | 160 | 140 | 520 | |
| 80 | 50 | 200 | 160 | 121 | 135 | 22 | 3 | 4 | 8-18 | 100 | 220 | 180 | 155 | 22 | 3 | 8-18 | 170 | 135 | 525 | |
| 100 | 65 | 235 | 190 | 150 | 160 | 24 | 3 | 4.5 | 8-23 | 125 | 250 | 210 | 185 | 22 | 3 | 8-18 | 195 | 175 | 690 | |
| 125 | 80 | 270 | 220 | 176 | 188 | 28 | 3 | 4.5 | 8-26 | 150 | 285 | 240 | 210 | 24 | 3 | 8-23 | 210 | 190 | 780 | |
| 150 | 100 | 300 | 250 | 204 | 218 | 30 | 3 | 4.5 | 8-26 | 175 | 310 | 270 | 240 | 26 | 3 | 8-23 | 255 | 230 | 838 | |
| 200 | 125 | 375 | 320 | 260 | 282 | 38 | 3 | 4.5 | 12-30 | 250 | 405 | 355 | 320 | 30 | 3 | 12-26 | 300 | 260 | 992 | |
| 250 | 150 | 450 | 385 | 313 | 345 | 42 | 3 | 4.5 | 12-34 | 300 | 460 | 410 | 375 | 30 | 4 | 12-26 | 350 | 320 | 1266 |

Model:
A51H-10C/A51H-16C/A51H-25C/A51H-40CSpecification:
DN25-DN200Pressure:
10PN-40PNMaterial:
cast steel
Model:
A42C-150LB/A42C-3000LB/A42C-600LB/A42P-150LB/A42P-3000LB/A42P-600LB/A42R-150LB/A42R-3000LB/A42R-600LBSpecification:
DN20-DN300Pressure:
150LB-600LBMaterial:
cast steel, stainless steel, bi-directional stainless steel
Model:
WA42Y-10C/WA42Y-16C/WA42Y-25C/WA42Y-40C/WA42Y-64C/WA42Y-100C/WA42Y-10C/WA42Y-16P/WA42Y-25P/WA42Y-40P/WA42Y-64P/WA42Y-100P/WA42Y-10C/WA42Y-16R/WA42Y-25R/WA42Y-40R/WA42Y-64R/WA42Y-100RSpecification:
DN15-DN400Pressure:
10PN-100PNMaterial:
cast steel, stainless steel, bi-directional stainless steel