MIL-HDBK-1164
(2)
Attach the string of 2-inch (50-mm) pipe to a hose with a
swivel connection at the top.
(3)
Lower the jetting tool into the screen. Turn on the high-
pressure pump and slowly rotate the jetting tool while raising and lowering it. The
forceful action of the high-velocity jets, working the water through the screen openings,
breaks up the clog.
(4)
Pump the well lightly while the jetting is under way in order
to remove the dislodged material. The well pump should pump out approximately 15
percent more water than is being added to the well by the jetting tool.
f)
Sonic Process Cleaning. Normally, this method is performed by
outside contractors. It consists of lowering a series of small, explosive charges on a
wire into the well and detonating them by means of an electrical charge at the surface.
The size of each charge depends on pipe size, thickness, grade, type, and condition.
The charges are placed on a connecting wire at calculated distances and are
detonated in a special time-delay sequence. Each charge, lasting only a fraction of a
second, creates an expanded gas bubble that produces a shock wave at its leading
edge as it rushes down the well column. As the wave strikes the well casing, it causes
strong vibrations that help loosen the clog. The expanding bubble also produces a
surging action that helps clean the screen. This action is repeated with the detonation
of each charge. Sonic processes are most effective in sandstone aquifers where
clogging may only extend 1 to 2 inches into the aquifer.
Caution: Do not use any other method of blasting for cleaning screens.
g)
Surging. Cleaning a well screen by surging is accomplished by a
method different from that used for surging a new well being developed. (See
par. 2.1.3 for a discussion of surging new wells.) This operation can be accomplished
by utility personnel, without pulling the pump and without expert help. Follow these
steps:
(1)
Disconnect the discharge of the pump and alternately start
and stop the pump. This operation raises the water in the pump casing and allows it to
fall again. The greater the distance to the static water level, the more effective the
operation. If the water level in the well stands at a high elevation, a surge pipe may be
attached to the discharge of the pump.
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