Common cleaning methods for water cooling systems

Water is a good cooling medium, but all kinds of water contains dissolved solids, gases and various suspended substances to varying degrees, in the water cooling system will cause such as sediment (scale, silt, corrosion products and biological sediments), corrosion, microbial (bacteria, algae) propagation and other problems, to the safe and efficient operation of equipment harm, specific performance in:

1. The heat transfer effect is reduced: the thermal conductivity of carbonate scale is only about 1% of that of carbon steel or copper, so when the scale and other sediments cover the heat transfer surface, the heat transfer efficiency will be greatly reduced.

2. Reduce the circulation water: sediments or microbial mud cover the wall of the heat exchange tube and even block the heat exchange tube, making the cross-sectional area and flux of the circulation channel smaller, thus further reducing the heat exchange effect.

3. Reduces the effectiveness of water treatment agents: sediments and microbial sludge prevent water agents from reaching metal surfaces and react with water treatment agents.

4. Accelerated corrosion: sediments and microorganisms promote the formation of concentrated corrosion batteries and the generation of corrosion under scale, which intensifies the corrosion rate of metals and shortens the service life of equipment.

5. Increased operating costs: heat conduction decreases, production efficiency decreases, and equipment operating costs increase.

Water cooling system cleaning, at present the most effective cleaning methods physical and chemical two methods.

 

The physical cleaning

Will be split into circulating water system such as the cooler, pipelines, tank cleaning, cooling towers, etc several parts. Main ShuaLa useful steel wire brush cleaning method, and using a special scraper, high pressure water jet cleaning, etc.

1. with wire brush pull brush cleaning, suitable for tube and shell heat exchanger cleaning. Remove both ends of the heat exchanger cover, plug the spiral wire brush into the heat exchange tube repeatedly pull brush, and then use slightly less than the heat exchange tube inner diameter of the round rod into the heat exchange tube, pull and poke, rinse with tap water.

 

2. The hard scale can be rolled by special scraper, which is connected to the soft shaft driven by the motor and inserted into the heat exchange tube, so that the special scraper is rolled in the tube edge scraping and washed out with water.

 

3. High pressure water jet cleaning, cleaning the heat exchange tube one by one with high pressure water gun. For pipelines, high pressure water jet with flexible nozzle can be used to clean them. For pools and towers, high pressure water jet cleaning efficiency is higher.

 

4. For sticky mud, it can also be cleaned by blowing off compressed air.

Advantages: can save agent when cleaning reagent cost, avoid the cleaning liquid discharge after chemical cleaning, there is less cleaning equipment corrosion.

 

Disadvantages: most of the physical cleaning methods need to be discharged after the equipment is shut down, disassembling the equipment can only be carried out, difficult to disassemble the pipeline, heat exchanger can not be physically cleaned, cleaning operator labor intensity, high technical requirements for workers, some methods are easy to cause damage to the equipment surface when the operation is not.

 

Chemical cleaning

Chemical cleaning is a method to dissolve, loosen, fall off or peel off the sediment in the cleaning equipment through the chemical reaction or dissolution of chemical agents. Chemical cleaning is also commonly used in conjunction with physical cleaning.

 

Chemical cleaning of water system can be divided into circulation method and soaking method. Circulation method is one of the most widely used methods, the use of the original system of water circulation, or temporary installation of pumps, cleaning tanks, etc., and the cleaning equipment to form a closed loop, continuous circulation of cleaning liquid, sedimentary layer and other constantly by the chemical action of fresh cleaning liquid and scouring and dissolution and fall off. Soaking method is suitable for some small equipment and blocked by sediment, and can not be recycled cleaning equipment.

 

The contents of chemical cleaning of water system circulation method are:
1. water flushing, the purpose is to wash away loose sediment, algae and corrosion products in the system.

 

2. Sterilization and algal cleaning: kill the microorganisms in the system and make the biological mud on the surface of the equipment peel off.

 

3. pickling: The use of acid cleaning agent and calcium carbonate scale and metal oxide chemical reaction, generate soluble substances and remove. In order to restrain the corrosion of metal by cleaning agent, corrosion inhibitor should be added in pickling.

 

4. alkali washing: the purpose of alkali washing is to remove the oil pollution and microorganisms in the system to ensure uniform pickling. Generally, when there is oil pollution in the system, alkali washing is needed, and new equipment is generally needed.

 

5. Water washing between each step: it is to remove the residual cleaning liquid and impurities in the system.

6. Rinsing: The floating rust formed in the water rinsing process of the cleaning system reduces the total iron ion concentration of the system to ensure the passivation effect.

 

7. passivation: the formation of a conductor film on the metal surface can inhibit the dissolution of metal, to prevent metal after pickling and oxygen in the air combined with rust, equipment after cleaning if temporarily not used, you need to passivation treatment.

 

8. pre-film: the purpose of pre-film is to generate a layer of corrosion resistant protective film on the surface of fresh metal after cleaning in the activated state.

 

Advantages: sediment can be completely removed, cleaning effect is good, in some cases can be non-stop cleaning, can not disassemble and physical cleaning is difficult to reach the parts of cleaning, cleaning operation is simple, than physical cleaning save labor.

 

Disadvantages: Choose the right cleaning care agent, improper operation or poor quality of the agent is easy to produce metal corrosion, cleaning waste liquid treatment problems, cleaning costs are relatively high.