MIL-HDBK-1164
(2)
Use an experienced and qualified contractor. Unless
otherwise directed by the utility manager, base personnel do not typically perform
acidizing operations. Be sure all people working on an acidizing project wear proper
protective clothing.
Caution: Before proceeding with the treatment, disconnect the well from
the distribution system.
(3)
Use an inhibited acid. Wells are most often acidized using
muriatic acid (commercial hydrochloric acid, 27 percent concentration) purchased with,
or to which has been added, an inhibitor. These inhibitors are proprietary compounds:
they keep the attack on the metal to a minimum but do not affect the reaction with
calcium carbonate. Select the inhibitor or inhibited acid to obtain the maximum
protection for the particular metal in the screen.
(4)
Add the acid carefully through a hose placed in the case
with its discharge end at the level of the screen. This procedure prevents dilution of
the acid and gives a concentration of about 15 percent at the screen.
(5)
In typical situations, leave the acid in the well for at least
5 hours. For quicker action, the acid may be heated, particularly if there is a flow of
water past the well screen.
(6)
After the acid treatment, pump the well to waste until the pH
of the water returns to normal.
Caution: Provide for neutralization of this wastewater or other safe
disposal until the water returns to normal.
(7)
Sulfamic acid (do not confuse with sulfuric acid) may be
used in place of muriatic acid. Sulfamic acid is a granular solid that is safe and easy to
store and handle. It may be dissolved in water at the job site to provide a strong acid
solution that will do the same cleaning job as muriatic acid. Although sulfamic acid
does not attack metals as rapidly as muriatic acid, inhibitors should still be used to
protect the casing. To dissolve iron oxide deposits on the screens, add 50 pounds
(22.5 kilograms [kg]) of salt (sodium chloride) for every 100 pounds (45 kg) of granular
sulfamic acid.
(8)
Reaction of the acid in the well produces carbon dioxide and
hydrogen. If iron sulfide is present in the well screen, hydrogen sulfide gas is also
produced. Hydrogen sulfide is a toxic gas. Provide adequate ventilation in pump
houses or other confined areas when acidizing the screens. It is recommended that
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