How does contamination occur in the Cooling Systems?

Contamination is the formation of particles other than calcite in the cooling water. It should be checked as there is a condition that will generally lead the system to be blocked and stopped. The main factors affecting contamination;

  • Sand, dust, mud and iron oxide particles
  • Lubricant
  • Corrosion products
  • Microbiological developments (bacteria, algae etc.)
  • Lime from feed water
  • Raw materials like rubber plastic etc. which may come from the system

Contamination can lead to clogging of the system and must be controlled as it is one of the important factors that increase corrosion. First of all, good quality feed water should be provided and corrosion lime prevention and microbiological struggle should be done well.

The contamination factor can change the flow regime of the system and surround the wall of the heat transfer pipes, creating an extra resistance for heat transfer. This reduces the efficiency of the system and reduces the cooling capacity. Contamination increasing over time is one of the biggest enemies of evaporators and thus cooling systems.

For evaporator and condenser water, the alkalinity value of the water pH degree, the amount of ions in the hardness and the circulating temperature are effective in corrosion and limestone formation in heat exchangers and other installation components. The recommended water properties for cooling systems are as follows.

  • Ammonium ions (NH4+) in water are very harmful to copper. These ions are one of the most important factors that negatively affect the working life of copper pipes. Ammonium ions (NH4+) must not be present in the water.
  • Chloride ions (Clˉ) cause small holes to form on the surface of copper pipes due to corrosion. Chloride ions in water should be below <10mg/l.
  • Sulphate ions (SO-4²) cause corrosion and small holes on the copper pipe surfaces. Percentage of sulfate ions in water (SO-4²) should be less than <30mg/lt.
  • Fluoride (Fˉ) ions in the water cause acid formation and corrosion. Its amount in the water should be below 0.1 mg/l.
  • Iron (Fe² + and Fe³+) ions in water combine with dissolved oxygen in the water and cause rust and plumbing sludge formation. Therefore, there should be no iron ions in the water. If the dissolved oxygen content in the water is less than <5mg/l, the dissolved iron content in the water should be less than <5mg/l.
  • There is a danger of acid and corrosion of silicon dissolved in water. Its amount in the water should be below <1 mg/l.
  • Total Water Hardness should be TH> 0.5mmol/l. Total Water Hardness is recommended to be between 1÷2.5mmol/l. The formation of some deposits on the inner surfaces of the copper pipes will limit the corrosion of the copper pipes. However, the high water hardness will lead to the formation of excessive amounts of limestone in the copper pipes, preventing water transfer and heat transfer. It is recommended that the Total Alkaline Metric Titer (TAC) of the water is <100.
  • Conditions that will change the state of oxygen in water should be avoided. It is harmful to make the water de-oxygenated by an inert gas such as Nitrogen and saturated with excess oxygen. These irregularities in the amount of oxygen in the water promote the formation of copper oxide and increase the amount of particles.
  • High Electrical Resistivity of water reduces the tendency of corrosion in the system. For this reason, it is recommended that the Electrical Resistivity of the Water be> 30 Ohm.m. Electrical Conductivity of water should be <20 ÷ 60 mS/m.
  • The ideal pH value of water at 20÷25ºC must be between 7<pH<8.

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Churchill
Churchill