A valve assembly 200 including a housing 202 with an internally projecting lip 226 that seals against an outer surface of a valve stem 220 inserted through it. A gas inlet 234a is provided above the lip 226 and a liquid inlet 212 is provided below the lip. The lip 226 thus ensures that a gas flow path and a liquid flow path are kept separate until the valve stem 220 is moved to an open position, at which point a liquid inlet hole 284 in the stem is brought into communication with the liquid inlet 212 in the housing and a gas inlet hole 286 in the stem is brought into communication with the gas inlet 234a in the housing for the fluids mix in an outlet conduit 280 in the stem. The arrangement means that there is no contact between the liquid and a sealing gasket 260, thereby avoiding swelling of the gasket that can cause the stem 220 to stick.一種閥件總成其包括一具有內部突出舌狀件的外殼，舌狀件頂靠著插入通過的一閥桿之一外表面而密封。在該唇狀件上方提供一氣體入口以及在該唇狀件下方提供一液體入口。該舌狀件因而確保一氣體流動路徑以及一液體流動路徑保持分開直至該閥桿係移至一開啟位置為止，於該點處位在該閥桿中的一液體入口孔係與該外殼中的該液體入口連通，以及位在該閥桿中的一氣體入口孔係與該外殼中的該氣體入口連通，用於在閥桿之一出口導管中流體混合。該佈置意指該液體與一密封墊片之間並無接觸，從而避免墊片增大會導致該閥桿黏附。
