In the purchase of back pressure valve, you should pay attention to the problems usually have the following aspects: 1. Pipe diameter DN6,8,10,15,20,25,32,40,50,65,80,100 ten Two models. 2. The inlet pressure 0.3MPa and 1.0MPa two series, import and export side pressure difference can be adjusted by adjusting the length of the spring. 3. The material is PVC (P), SS304 / 316 stainless steel (S), carbon steel (A) 4. Import and export connection to provide internal thread, flange, hose connector in three ways to choose from.