25 May 2005
Remedial Cleaning. Remedial cleaning is performed to restore a water
system that is fouled with scale, corrosion products, or microbiological biomass due to
inadequate or ineffective water treatment. The problem could have resulted from using
improper chemical technology, failure to maintain treatment levels within control
parameters, or the failure of pre-treatment equipment. The cleaning agents used for
remedial cleaning usually include acids, chelants, neutralizing agents, and specialty
Safety and Environmental Issues. Remedial cleaning may pose safety
issues for personnel handling acids, caustics, and various chemicals. There could also
be environmental concerns associated with chemical disposal. Inexperienced personnel
should not perform the chemical cleaning of an industrial water system.
Contracting Cleaning Services. For some cleaning jobs, such as large
boilers and cooling towers, it may be advisable to engage a service company
specializing in chemical cleaning. If the cleaning service is contracted, it is vital that
adequate lines of communication be established, and that safety procedures employed
by the service company comply with military regulations. An orientation meeting should
be scheduled between military installation personnel and the service company
representatives. At that time, the scope of the work can be defined, proper procedures
initiated, and the nature of the hazards described thoroughly. The use of proprietary
cleaning chemicals or chemical formulations may be involved; disclosure of the use and
nature of these chemicals should be made at the orientation meeting. Military policies
and restrictions can also be explained. The inspection of equipment after cleaning is
usually the final step in the overall cleaning process.
Reasons for Cleaning. Maintenance of an effective water treatment
program is essential to minimize scale and corrosion problems in industrial water
systems; however, scale and deposits that form will require remedial cleaning
(descaling). If not removed, these scale and water-caused deposits may impact the
safety of operations personnel, interfere with heat transfer, and cause excessive
damage to, or destruction of, the water-using equipment. Cleaning is not appropriate for
the removal of deposits when corrosion of the system has advanced to the point where
a large number of leaks may result from the removal of the deposits.
Types of Deposits. The deposits that occur in water systems can be
inorganic mineral salts and corrosion products or organic (oily) or biological in nature.
Deposits range in composition from very dense crystalline structures, to very porous
and loosely bound materials, to gelatinous slimes. Most of the deposits formed from
water constituents consist of corrosion products such as iron and copper oxides,
mineral scales, or mixtures of these materials.
Waterside Deposits Located in Heat Exchangers. Water deposits
located in heat exchangers are usually carbonate-based scales, while steamside
deposits may be a mixture of metallic oxides and organic residuals from lubricating oil,
particularly where reciprocating-type engines are used. In steam systems, the oxides