The NK type, with its reduced body length and its consequent reduced weight, offesr significant cost savings compared with the long pattern NB and ND types. The unique ring disc design ensures that the disc remains light and responsive even in large sizes, which is essential for rapid non-slam closure. Mounted on a multiple spring and radial guide assembly, the disc moves freely without the frictional forces. Combining two ring-shaped annular flow paths with the excellent pressure recovery properties provided by the diffuser, the minimal pressure drop across the Type N valves gives lifetime energy savings when compared to more conventional check valve designs.