assembly 42 the sealing arrangement comprises a fixed ring 70 formed as an annular body having three concentrically spaced plates 72 74 and 76 that are joined at their upper ends by annular end closure 78 the plates 72 74 and 76 cooperate to define a pair of downwardly open concentric spaces 80 and 82 respectively the fixed ring 70 is detachably secured to the top wall 38 of housing 36 about the opening 40 by means of threaded connectors not shown or the like that pass through aligned openings in the housing and in an annular flange 84 which extends outwardly from the exterior surface of the radially outermost plate 72 cooperating with the fixed ring 70 is a movable ring 86 formed as an annular body having two plates 88 and 90 that are upstanding from an annular bottom closure 92 plates 88 and 90 are concentrically spaced with respect to each other to define a liquid receptacle 94 therebetween the annular plates 72 74 and 76 on fixed ring 70 and plates 88 and 90 on movable ring 86 are each formed of diameters to permit plates 88 and 90 on the movable ring to extend into the spaces 80 and 82 in the fixed ring and for the intermediate plate 74 on.