Swing check valves, also known as a one-way valve or check valve, and its role is to prevent the line of medium back. Opening and closing pieces by medium flow and strength to turn itself on or off, in order to prevent the media called backflow check valve. Check valves are automatic valves, mainly used for one-way flow of media channels, only allowing media to flow in one direction, in order to prevent accidents. First, use: swing check valves for nominal pressure pn1.0mpa ~ 42.0mpa, class150-2500; nominal diameter dn15 ~ 1200mm, nps1 / 2 ~ 48; working temperature of various pipeline of -196 ~ 540 ℃ used to prevent the media back. By the choice of different materials, applicable to a variety of media water, steam, oil, nitric acid, acetic acid, strong oxidizing medium and urea. Second, the main material: carbon steel, low temperature steel, duplex steel (f51 / f53), titanium, aluminum, bronze, Inconel Seoul (inconel625), ss304, ss304l, ss316, ss316l; chromium-molybdenum steel, Monel ( 400/500), 20 # alloy, Hastelloy and other metal materials Third, standards and specifications 1, the design and manufacture: api594, api6d, jb / t8937 2, length of the structure: api594, api6d, din3202, jb / t8937 3, the pressure A temperature rating: snsib16.34, din2401, gb / t9124, hg20604, hg20625, sh3406, jb / t74 4, test and inspection: api598, jb / t9092 four structural features a short length of the structure, the length of the structure only the traditional method Portland valve 1/4 to 1/82, small size, light weight, its weight is only the traditional flange check valve 1/4 to 1/203, the valve closed fast, small water hammer pressure 4, horizontal or vertical pipe can be used, easy installation 5, flow smooth, fluid resistance 6, sensitive, good sealing performance 7, the valve stroke is short, the impact of small off valve 8, the overall structure is simple and compact, attractive appearance 9 , long life, high reliability five, swing check valve action principle and structure described a principle: by moving up and down the cylinder plug to help quickly open and close the valve sealing surface to achieve 2 Structure Description: a structure in the form of: Swing single valve b Drive: hydraulic c Connection: threaded connection d valve opening and closing is controlled by a pneumatic device to accelerate the valve opening and closing speed.