DOUBLE ISOLATION AND BLEED TRUNNION MOUNTED BALL VALVES TO NEW API-6D 24th (DIB-Type B to §H12)[R] Author: Alberto Seveso Company: LCM Italia S.p.A. Download Abstract Traditional API-6D trunnion mounted ball valves equipped with bidirectional seat (e.g. double piston effect) are able to provide DIB Type B function when each seat is tested individually.