按照介质排放方式的不同， 安全阀又可以分为全封闭式、半封闭式和开放式等三种。
1.全封闭安全阀
全封闭式安全阀排气时，气体全部通过排气管排放，介质不能间外泄漏，主要用于介质为有毒。易燃气体的容器。
2.半封闭式安全阀
半封闭式安全阀所排出的气体一部分通过排气管，也有一部分从阀盖与阀杆间的间隙中漏出，多用于介质为不会污染环境的气体的容器。
3.开放式安全阀
开放式安全阀的阀盖是敞开的，使弹簧腔室与大气相通，这样有利于降低弹簧的温度，主要适用于介质为蒸汽，以及对大气不产生污染的高温气体的容器。
北京华德液压全系列 具体型号及报价请联系客服
北京华德换向阀部分型号如下：
4WE6H61B/CW220-50N9Z44WEH10D20B/6AW220-50NETZ4
4WE6H61B/CW220-50N9Z54WEH10D20B/6AW220-50NETZ5
4WE6H61B/CW220-50N9Z5L4WEH10D20B/6AW220-50NETZ5L
4WE6H61B/CW220-50NK44WEH10D20B/6AW220-50NEZ4
4WE6H61B/CW220-50NZ44WEH10D20B/6AW220-50NEZ5
4WE6H61B/CW220-50NZ54WEH10D20B/6AW220-50NEZ5L
4WE6H61B/CW220-50NZ5L4WEH10D20B/6AW220-50NTZ4
4WE6J50B/AG24N 4WEH10D20B/6AW220-50NTZ5
4WE6J50B/AW220-50N4WEH10D20B/6AW220-50NTZ5L
4WE6J50B/BG24N 4WEH10D20B/6AW220-50NZ4
4WE6J50B/BW220-50N4WEH10D20B/6AW220-50NZ5
4WE6J61B/CG12N9DKL4WEH10D20B/6AW220-50NZ5L
4WE6J61B/CG12N9DL4WEH10D20B/6EW220-50NETZ4
4WE6J61B/CG12N9Z44WEH10D20B/6EW220-50NETZ5
4WE6J61B/CG12N9Z54WEH10D20B/6EW220-50NETZ5L
4WE6J61B/CG12N9Z5L4WEH10D20B/6EW220-50NEZ4
4WE6J61B/CG12NDKL4WEH10D20B/6EW220-50NEZ5
4WE6J61B/CG12NDL4WEH10D20B/6EW220-50NEZ5L
4WE6J61B/CG12NZ44WEH10D20B/6EW220-50NTZ4
4WE6J61B/CG12NZ54WEH10D20B/6EW220-50NTZ5
4WE6J61B/CG12NZ5L4WEH10D20B/6EW220-50NTZ5L
4WE6J61B/CG24N9DKL4WEH10D20B/6EW220-50NZ4
4WE6J61B/CG24N9DL4WEH10D20B/6EW220-50NZ5
4WE6J61B/CG24N9Z44WEH10D20B/6EW220-50NZ5L
4WE6J61B/CG24N9Z54WEH10E20B/6AW220-50NETZ4
4WE6J61B/CG24N9Z5L4WEH10E20B/6AW220-50NETZ5
4WE6J61B/CG24NDKL4WEH10E20B/6AW220-50NETZ5L