A Guide To Water Well Casing and Screen Selection   -   27

8.10  Diameter Reductions

Occasionally reductions are made in diameter between casing and/or screen sections. Regular bell pipe reducers have been used, but they are expensive, and the reduction is rather abrupt. Reduction cones have been fabricated from pipe by torch-cutting segments from the pipe, bending the remaining segments inward, and welding the new seams together (orange peeling). This is a fairly expensive operation and results in a non-uniform, frequently weak structure. A better solution consists of the use of a fabricated tapered cone with a short stub joint of each diameter casing welded at each end. These stubs may be machined for greater alignment accuracy.

While no supporting data exists, it has been suggested that the length of the cone of the reducing section should be at least ten times the difference in diameter of the two ends for hydraulic efficiency and strength. It may be added that a longer tapered section or cone mitigates bridging at that point when gravel is introduced from the surface.

8.11  Bottom Plugs

A bull nose or plug is always attached to the bottom of casing and screen strings installed in gravel envelope wells. These may be fabricated by orange peeling a short joint of casing to a one to three foot taper, depending on diameter. Semi-elliptical tank ends, readily available and inexpensive, provide a convenient fulfillment of this requirement

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