api5000API 5000, 10000 are used in reference to wellhead 'christmas tree' pressure ratings as well used for the wing valve, master valve ratings. There may be hher classes asAPI 6A TYPE 6B 5000 PSI Blind pipe flanges are used to seal the end of a piping system or pressure vessel openings to prevent flow.API 6A TYPE 6B 5000 PSI Blind flanges are mainly