TZA1 series Bellows sealed single seat regulating valve applies roof guide unbalanced structure, which contains characteristics of high strength, heavy load, S-shaped runner, small loss of pressure drop, high flux coefficient, wide adjustable range, high accuracy of flow characteristic. Double sealed bonnet by both bellow and packing, it primarily avoids the possibility of medium leakage. By using hold-down seat on valve cage, it resolves some common problems of traditional thread screw in valve seat, such as uncomfortable disassembling, and large amount of leakage, and also extends the working life. With flow-open designing, fluid medium trends to valve’s opening direction, so it has good controllability in small opening, and small distortion of flow characteristic. TZA1 series regulating valve is suitable for controlling the flow pressure of toxic or valuable medium. In certain conditions, special cage can be applied for noise reduction and anti-cavitation.