Double walled screen-filter with perforated joints

摘要

A well screen-filter includes a pair of substantially spaced concentric screens defining an annular filtering space therebetween, connected with perforated joint(s) closing the lower end of the filtrating space. The annular space is filled with filtrating materials (gravel or synthetic balls) as a pack and an upper joint acts as a cover cap of the annular filtrating space to seal the pack. The lower perforated joint includes holes for passage of fine particles to a sedimentation tube, preventing clogging of the pack and enabling proper functioning of the double walled screen-filter.