Abstract: A variable orifice dual gate valve having two opposed slidable valve gates in overlapping sliding contact relationship. Inner orifice edges of these plates coact to form a variable size orifice in the valve body upon simultaneously sliding of the valve gates in opposite directions through manipulation of a gear and screw drive mechanism. The gear and screw drive mechanism includes a handle drive shaft connected at an exposed end to a valve handle and a drive gear is secured to the other end of the handle drive shaft for axial rotation. This drive gear is meshed in driving engagement with two driven gears that in turn are respectively secured to drive right hand lead screw and left hand lead screw shafts. A right hand follower nut and a left hand follower nut are respectively threadably received on these lead screw shafts and gate slide drive shafts are in turn secured to these nuts respectively for follower movement with the nuts.

Abstract: A self aligning tube alignment bar for aligning and retaining a vertical series of boiler tubes in parallel. The tube alignment bar is comprised of two elongated parallel bar halves having a series of opposed recesses with interengaging protrusions therebetween to initially loosely confine the series of tubes respectively in a separated series. Thereafter the two halves are drawn together by bolts causing the two alignment bar halves to have their protrusions interengage and thereby guide the two halves together in clamping engagement such that ultimately the tubes are retained in a parallel series.