Swing Check Valves Sap Cast Steel Check Valves have been designed to meet the requirements of BS 1868 ASME B 16.34API 6D-ISO14313. Butt weld end dimensions conform to ASME B 16.25, The Seat-rings are cylindrical bottom seated type having ample cross section for strength are provided with welded in and threaded Seat-rings will be supplied on request. In case of SS valves the Seat-rings are integral to Body.