A Guide To Water Well Casing and Screen Selection   -   20

7.4  Bridge Slot

Another well screen produced in the United States and overseas is referred to as "bridge slot". This screen is manufactured on a press from flat sheets or plates. The slot opening is usually vertical and provides two orifices, longitudinally aligned to the axis. The perforated steel sheets or plates are then rolled into cylinders and the seam welded. Normally five foot sections of bridge slot screen are welded together into longer lengths suitable for field installation.

Bridge slot screen is usually installed in gravel envelope wells. Its chief advantages are reasonably high area of opening and minimum frictional head losses ate relatively low cost. One important disadvantage is low collapsing strength due to the large number of vertically oriented slots. The manufacturing process is limited with respect to wall thickness and .250 inch is the maximum generally available. Since gravel control is more difficult with any vertical opening as compared to a horizontal opening, a smaller aperature size relative to the pack material should be selected.

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