Closed System Water treatment Additives
Our range of chemical treatments includes : Molybdate/Phosphonate Corrosion Inhibitor, Nitrite Inhibitor, Copper Corrosion Inhibitor, All Organic Scale Inhibitors, Non-oxidising Biocide, Bio-Dispersant, Cleaners
Water Treatment Additives
In a closed system, water circulates in a closed cycle and is subjected to alternate cooling and heating without air contact. Heat, absorbed by the water in the closed system, is normally transferred by a water-to-water exchanger to the recirculating water of an open recirculating system, from which the heat is lost to atmosphere
Closed Recirculating Cooling applications includes :
- Close recirculating cooling water systems (chillers)
- Close recirculating heating water systems
- Gas engines and Compressors
- Power Diesel engines in stationary and locomotive service
- Automobile cooling system
- Air conditioning chilled water systems to transfer the refrigerant cooling to air washers
Advantages of Closed Systems
Closed recirculating systems have many advantages.
- They provide better control of temperatures in heat-producing equipment, and their small makeup water requirements greatly simplify control of potential waterside problems. Makeup water is needed only when leakage has occurred at pump packings or when water has been drained to allow system repair.
- High-quality water can usually be used for makeup, and as a result, scale deposits are not a problem.
- Closed systems are also less susceptible to biological fouling from slime and algae deposits than open systems.
- Closed systems also reduce corrosion problems drastically, because the recirculating water is not continuously saturated with oxygen, as in an open system.
Some closed systems, such as chilled water systems, operate at relatively low temperatures and require very little makeup water. Because no concentration of dissolved solids occurs, fairly hard makeup water may be used with little danger of scale formation. However, in diesel and gas engines, the high temperature of the jacket water significantly increases its tendency to deposit scale. Over a long period, the addition of even small amounts of hard makeup water causes a gradual buildup of scale in cylinders and cylinder heads.
Untreated systems can suffer serious corrosion damage from oxygen pitting, galvanic action, and crevice attack. Closed cooling systems that are shut down, oxygen can enter the water until its saturation limit is reached. When the system is returned to high-temperature operation, oxygen solubility drops and the released oxygen attacks metal surfaces. The metallurgy used in constructing modern engines, compressors, and cooling systems includes cast iron, steel, copper, copper alloys, and aluminum as well as solders. If bimetallic couples are present, galvanic corrosion may develop.
Some times when nitrite base treatments programs used, nitrites are oxidized by microorganisms. This can lead to sever biological fouling.
The three most reliable corrosion inhibitors for closed cooling water systems are :
Generally, the chromate or molybdate types have proven to be superior treatments. For mixed metallurgy systems, the molybdate inhibitors provide the best corrosion protection.
Molybdate treatments provide effective corrosion protection and an environmentally acceptable alternative to chromate inhibitors. Molybdates are thermally stable and can provide excellent corrosion protection in both soft and hard water. Molybdate inhibitors should not be used with calcium levels greater than 500 ppm.
Nitrite- molybdate-azole blends inhibit corrosion in steel, copper, aluminum, and mixed-metallurgy systems. System pH is normally controlled between 7.0 and 9.0. Recommended treatment control limits are 200-300 ppm molybdate as MoO4.
Nitrite is another widely accepted nonchromate closed cooling water inhibitor. Nitrite concentrations in the range of 600-1200 ppm as NO2- will suitably inhibit iron and steel corrosion when the pH is maintained above 7.0. If aluminum is also present, the corrosion problem is intensified, and a treatment level of 10,000 ppm may be required. In all cases, the pH of the circulating water should be maintained in the alkaline range, but below 9.0 when aluminum is present.
One drawback to nitrite treatments is the fact that nitrites are oxidized by microorganisms. This can lead to low inhibitor levels and biological fouling. The feed of nonoxidizing antimicrobial may be necessary to control nitrite reversion and biological fouling.
Monitoring and Testing
Effective corrosion control monitoring is essential to ensure closed system reliability. ADTEC Chemicals provides well planned monitoring program which include the following:
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