A.關(guān)閉放空閥之后,關(guān)閉進液閥; B.關(guān)閉進液閥后,關(guān)閉放空閥; C.關(guān)閉進液閥,暫緩關(guān)閉放空閥; D.關(guān)閉放空閥后,暫緩關(guān)閉進液閥
A.上游; B.下游
A.止回閥 B.節(jié)流閥 C.截止閥 D.閘閥