25 May 2005
Cooling Tower Distribution Deck. It is important to look for the presence
of algae, debris, or anything that has plugged water distribution holes causing an
uneven water flow through the tower, thus lowering tower efficiency. Clean plugged
holes and replace damaged water distribution spray nozzles.
In addition, look for the presence of algae deposits. If algae deposits are
present, increase the level or frequency of biocide or algaecide treatment, and cover the
deck if uncovered.
Cooling Tower Fill, Air Intake Slats, and Basin
Scale Deposits on Cooling Tower Fill. The presence of deposits,
particularly on cooling tower fill, can be established by removing some fill to determine if
partial plugging has occurred. Scale can range in color from white to gray or reddish
depending on the scale composition. Scale formation on the cooling tower fill usually
indicates a severe scaling situation. If possible, obtain a sample of the scale for analysis
and, based on the result, select a scale inhibitor for that specific scale.
Scale Deposits on Air Intake Slats. Scale can form on the air intake
slats of a cooling tower. This buildup is due mostly to water splashing and evaporating,
causing deposition of soluble salts or minerals. This situation does not indicate a serious
problem. These deposits can be, and should be, washed off periodically, but ideally not
into the cooling tower basin. Chemical treatment can provide some reduction in the
Slime Deposits. Slime deposits (microbiological) can sometimes be
detected by feeling below the water level on the distribution deck and on the walls of the
cooling tower basin. Most microbiological growth will have a slimy feel. If slime deposits
are present, increase biocide frequency or increase the dosage.
Suspended Solids. The purpose of a dispersant is to keep particulate
solids in suspension and to prevent them from settling or from adhering to heat transfer
surfaces. Adequate water flow is required to prevent them from settling. Particulate
solids in suspension are removed with the blowdown water. The tower water should be
turbid if the dispersant is doing its job. Keep the cooling tower sump clean of SS by
cleaning periodically and using a filter.
Corrosion Test Coupons. When removing corrosion coupons, always
note and record the visual appearance with regard to the presence of scale, rust, or
biomass. Take photographs of the corrosion coupons. Submit (or evaluate) coupons for
corrosion rate and for the type of corrosion that is occurring.
Inside Surface of Heat Exchanger Tubes. To effectively examine the
inside (water-contacted) surfaces of heat exchanger tubes, a boroscope is needed
because only a few inches of the interior can be seen visually using a flashlight. Scale
deposits, typically hard and tightly adhered to the tube surface, range in color from white