Acid Cleaning. In the coil model, scale generally may be
dissolved quickly by immersing the coil in a 20 percent solution of inhibited muriatic
acid (commercial hydrochloric acid). Wash the coils thoroughly in water before
reinstalling them in the evaporator.
Zinc Plate Replacement. Replace the zinc plates when they
have been reduced to about one-quarter of their original size.
Condenser and Cooler Tube Cleaning. Clean these tubes
(if used) by flushing, wire brushing or scraping, and flushing again before reinstalling
Shutdown Protection. If the plant is to be shut down for an
indefinite period and is subject to freezing conditions, remove all water from all parts of
Flash-Type Evaporators. Specific maintenance instructions are
provided by the manufacturer. The following procedures are the recommended
Check the evaporator stages for corrosion or encrustation
each quarter; clean and repair the evaporator as necessary.
Check the steam tube side of the evaporator twice a year
and repair it if necessary.
Each year, inspect all parts of the unit (both interior and
exterior) for signs of deterioration, and inspect the piping and valves. Repair or renew
parts as necessary; paint interiors.
Vapor-Compression Distillation Units. Detailed maintenance procedures
are found in the manufacturer's instructions. The following procedures are the
After 200 to 400 hours of operation, check the evaporator for
corrosion or encrustation. If the tubes are encrusted, use either chemical or
mechanical means for scale removal. Mechanical cleaning is used for hard scale that
cannot be removed by chemical treatment.
For chemical treatment, add sodium bisulfate directly, or in
solution, to the evaporator. Sulfuric acid and inhibited muriatic acid are better than
sodium bisulfate; however, in general they should be used only if approved by the utility