Modern Gasworks Practice

584 MODERN GASWORKS PRACTICE take a downward path. Providing that alternating up and down travel is not desired, the easiest means is that of merely transposing the long outlet pipe, which extends above the grids in the box to the miet main. Special valves, such as Milbourne’s (Fig. 352a and b), can now be had for reversing the direction of flow at will, whilst Dempster’s patent device, which is self-explanatory, is shown in Fig. 353. The Sadler-Cockey valve (Fig. 354) is a new departure which permits of working on either the backward or forward principle of rotation, and either upwards or down- Handwheel (Removable) Position ol Handwheel-when not in Use Gas ________ Inlet Fig. 353. - Dempster’s Reversing Valve-Box. Fig. 354.—The Sadler-Cockey Reversible Valve. wards through the material. The valve certainly gives great elasticity in the operation of the purifiers ; for instance, the boxes can be worked flrstly in downward direction and backward rotation, while the whole stream can be changed immediatelv into an upward and forward rotation. Thus, with four purifiers a variation of thirty-two changes is possible.