(1) vacuum valve: the working pressure below standard atmospheric pressure valve.
(2) Low pressure valve: nominal pressure PN ≤1.6Mpa valve.
(3) pressure valve: PN nominal pressure is 2.5Mpa, 4.0Mpa, 6.4Mpa valve.
(4) high-pressure valve: nominal pressure PN is 10.0Mpa ~ 80.0Mpa valve.
(5) high pressure valve: nominal pressure PN≥100.0Mpa valve.