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Cooling tower and heat exchanger cleaning process and method

November 5, 2021

In the refrigeration industry, cooling towers are mainly used for condensation and heat dissipation in cold storage, air conditioning, heat pumps and other fields. Using water as the circulating coolant, the cooling water in the tower heats up in contact with the air flow to produce steam, volatilizes away the heat, and is discharged into the atmosphere, which plays the role of evaporative heat dissipation, lowering the water temperature, and ensuring the normal use of the system.

 

The cooling tower is exposed to the outside for many years, and the fan’s adsorption power is very strong, so that a large amount of sand and dirt will enter the tower. Long-term operation will slowly reduce the cooling capacity of the cooling tower. Sand and dirt can also easily enter the cooling water system, which will directly affect the normal cooling of the cooling water system. Therefore, in order to ensure the normal operation of the cooling water system, it is recommended to clean the cooling tower regularly.

 

Cooling tower cleaning process

 

1. Water cleaning

The purpose of water flushing is to flush out loose dirt such as dust, sand, shed algae and corrosive substances in the system as much as possible with a large flow of water, and to check the leakage of the system at the same time. The flow rate of the flushing water should be greater than 0.15m/s. After the flushing is qualified, the flushing water in the system will be drained.

 

2. Stripping and cleaning of sterilization and algae killing slime

The purpose of sterilization and algae cleaning is to kill the microorganisms in the system and to peel off the biological slime attached to the surface of the equipment. After draining the flushing water, add a bactericidal and algaecide to the system for cleaning, and stop cleaning when the turbidity of the system reaches equilibrium.

 

3. Descaling and cleaning of cleaning fluid

The role of the cleaning fluid is to use the cleaning agent to dissolve the scales and oxides in the operating system and dissolve in water. The cleaning agent is added to the central air-conditioning operating system, and the circulating pump cleans and discharges at the highest and lowest points to avoid air blockage and shower blockage, which will damage the cleaning effect. The concentration of the cleaning solution, the concentration of metal ions (Fe2, Fe3, Cu2), temperature and ph should be checked regularly.

 

4. Rinsing after cleaning

The purpose of this water flushing is to flush out the remaining cleaning fluid and impurities during cleaning. The flushing is to not disconnect the pilot shower to flush out the impurities and residual fluid deposited in the short pipe. Flushing is to continuously test the PH value and turbidity, and finish the flushing when the PH value and turbidity tend to be flat.

 

5. Pre-filming

The function of the pre-film is to make the metal surface or the metal surface damaged by the protective film after cleaning, forming a complete anti-corrosion protective film.

 

Non-stop neutral cleaning

 

In the normal operation of the unit, the neutral cleaning agent is added to the cooling water and the refrigerant water system for circulating cleaning for about 30 days to release the cleaning liquid, and the cleaning process with the maintenance agent is over. The cleaning time of this scheme is relatively long, but it can be carried out under the normal operation of the unit, and will not affect the normal operation of the unit. Because the cleaning fluid is neutral, it does not cause corrosion to the system and equipment. During the cleaning process, the dirt in the system slowly dissolves, and no scale flakes will be generated after cleaning to block the filter screen.

 

Condenser and evaporator cleaning

 

The condenser and evaporator are important parts of the refrigeration unit. Its heat exchange effect directly affects the refrigeration effect. The main factor that affects the heat exchange effect is to keep the copper tubes inside the condenser clean, especially to remove the copper tubes on the inner wall. Hard dirt, soft dirt and various impurities; the most commonly used is to use chemical cleaning. It can very effectively remove the cleaning of the heat exchange surface of the heat exchanger in the copper tube, which is a prerequisite for chemical treatment.

 

Operating procedures:

 

  1. Close the water inlet and outlet valves, open the drain valve, and check the closing conditions of the inlet and outlet valves.

  2. Open the end cover to take some scale, and use the descaling agent to do descaling tests with different concentration ratios.

  3. According to the method of low in and high out, correctly connect the cleaning pump.

  4. ​Use an external water pump to fill the bucket with water, and start the cleaning pump to circulate until the water is stable.

  5. ​Slowly add the descaling agent to the bucket in stages, and rinse with tap water repeatedly after the cycle.

  6. ​Rinse and clean the pump with tap water.

  7. ​Open the end cover and use the gun gun to pass the gun.