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ELECTRICAL EQUIPMENT 



The details of a filter commonly used are shown in Fig. 202, 

 and the detail of the filter units in Fig. 203. It is the devel- 

 opment of this type of filter unit which has made possible the 

 continuous filtration of the enormous quantities of oil required in 

 modern hydro-electric plants. As will be noted from Fig. 202, 

 this design permits of installing a very large amount of filtering 



FIG. 203. Peterson Filtering Unit, Showing Method of Placing 

 Bag Over Frame. 



surface in a comparatively small space, and inasmuch as the cloth 

 on individual units is free from folds or plaits every square inch 

 of it is effective in filtering the oil. Each unit consists of gal- 

 vanized wire screens held in a metal frame. The cloth is in the 

 form of a bag which is brought up over the top of the filter unit and 

 retained in place by a cover which is held down by two thumb 



