The safety valve A27TW-2Q produced by Changsha No.1 Fan Co., Ltd. is generally of metal-sealed type, whose seat and spool are assembled by mutual grinding, and are not affected by environmental humidity and temperature when in use. However, if there is foreign matter attached around the valve seat, the foreign matter will be adsorbed to the contact surface when the valve spool is in action, thus forming the cause of valve leakage. In addition, pay attention to whether the safety valve is subject to shock during handling, which is also the cause of spool leakage. Safety valve A27TW-2Q model is not much, but the corresponding Roots fan caliber is more. SVF-32 safety valve is used DN50-100 fan caliber, SVF-50, SVF-80, SVF-100 respectively, corresponding to the fan caliber model is DN125-150, DN200, DN250-400, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve, safety valve. SVF-50, SVF-80, SVF-100, respectively, corresponding to the fan caliber models are DN125-150, DN200, DN250-400, safety valves A27TW-2Q is generally the above types of models.