17
Cleaning Methods
Cleaning requirements fall into two classes, scale
removal and biological cleaning. Scale removal
may be accomplished chemically or mechanical-
ly. Biological cleaning is accomplished with an
isopropyl alcohol solution. For best results all
solutions and water should be heated. The vari-
ous methods of cleaning are described below:
Soft Scale Removal.
Soft scale may be re-
moved with a stiff bristle brush. After cleaning, all
scale particles should be flushed out with water.
Hard Scale Removal.
Hard scale may be re-
moved by using a 10% solution of inhibited HCI.
This acid cleaner is available commercially or
may be prepared using 20 parts water and 6
parts 30% HCI. When using the acid, do not
allow the acid to remain in contact with the part
for more than 20 minutes. Flush the part thor-
oughly after using the acid cleaner. A 5% Sodium
Bicarbonate solution may be used to remove any
acid left on the part.
Organic Scale and Sludge Removal.
If the
scale has a dark brown or black color, it may be
formed from organic impurities present in the
feedwater. This type of scale may be removed
with a strong detergent solution. The detergent
solution should be allowed to be in contact with
the scale or sludge for 24 hours. Rinse off the
parts with water after cleaning.
Silica Scale Removal.
Silica scale is usually
clear and shiny and hard to detect visually. It is
very hard and cannot be removed with an acid
solution. Silica scale formation can be reduced
by controlling the quality of the feedwater by rout-
ing it through a mixed bed deionizer. It is best re-
moved with a blunt instrument.
Maintenance and Servicing
Note
If desired, 10% solutions of sul-
famic or acetic acids may be
used instead of the HCI.
Sulfamic and acetic acids have
an advantage over hydrochloric
acid in that they will not corrode
the metal parts being cleaned.
Under no circumstances
should any concentrated acid
be allowed to come in contact
with tinned surfaces.
Warning
Always wear protective clothing
and eye shields when handling
acid. Disconnect from the power
supply prior to maintenance and
servicing. Refer servicing to
qualified personnel.
