25 May 2005
Table 4-1. Summary of Scale Control Methods
1. Solubilize using phophonates.
2. Solubilize using polymers (polyacrylate,
3. Form sludge using specialty polymers.
1. Solubilize using phosphonates.
2. Solubilize using specialty copolymers or terpolymers.
Solubilize using copolymers of acrylate and acrylamide.
Maintain water chemistry of: pH < 9.0, magnesium
hardness < 500 ppm, and silica < 100 ppm.
1. Maintain water chemistry with silica < 150 ppm.
2. Solubilize with silica-specific polymer.
Cooling Water Fouling. The term "fouling" refers to the deposition of
materials that are normally held in suspension in the cooling water: mud, silt, and other
SS brought into the system with the makeup water; dust, dirt, and debris scrubbed out
of the air passing through the tower; product leakage such as oils; corrosion products
or all of these materials can be present in the cooling water.
Fouling Control. Fouling from mud, dirt, and corrosion products can be
controlled by the addition of a water-soluble polymer dispersant, such as a polyacrylate.
The addition of about 4 to 5 ppm of active polymer, together with sufficient water
velocity (e.g., 1 meter per second [3.28 feet per second]), can keep foulants in
suspension and prevent them from being deposited on heat transfer surfaces. Higher
dosages (5 to 20 ppm) of active polymer can be required for heavily fouled systems. It is
best to reduce the loading of SS by mechanically removing them from the system
through blowdown, filtration, and physical sump cleaning. Removing oil or oily materials
requires a non-foaming surfactant. Paragraph 4-4 describes prevention of fouling by
biological organisms. Table 4-2 summarizes foulant control methods.
Table 4-2. Summary of Foulant Control Methods
1. Disperse using polymers and maintain adequate flow.
Mud, dirt, corrosion
2. Form sludge using specialty polymers.
Disperse using a non-foaming surfactant.
MICROBIOLOGICAL DEPOSITS AND CONTROL. Microbiological
organisms are composed of three classes: algae, bacteria, and fungus. Large biological