Water coolers are also called shell-and-tube heat exchangers or shell-and-tube heat exchangers. They are mainly used in plastic machinery, die-casting machinery, air compressors, bottle blowing machines, hydraulic presses, hydraulic systems, as well as chemical, petroleum, electricity, printing and dyeing, textile and other industries. They meet the energy conversion requirements of two cold and hot fluids in the process, and at the same time recover waste heat resources to reduce energy costs for enterprises.
Corrosion, scaling and microorganisms are the three major hazards of circulating water systems. In order to extend the service life of water coolers, ensure the normal operation of the equipment, reduce the production and operation costs of enterprises, and reduce the damage to the environment in the production of enterprises, it is necessary to analyze the scaling and corrosion mechanism of water coolers, analyze the causes of the corrosion mechanism, and explore the corresponding anti-corrosion solutions to improve the structure of water coolers and the occurrence of corrosion.
1. Mechanism of scaling corrosion of water cooler
The scaling substances in the water cooler system are mainly heavy hydrochloride structures. The higher the concentration, the more water evaporates. When the concentration reaches a certain value, a large amount of water will precipitate from the water body and form scale. Under normal circumstances, when air contacts cooling water, the dissolved oxygen in the water will reach a saturated state. Under the influence of high temperature conditions, the metal bone will be corroded. If the situation is serious, it may even cause perforation problems. If such problems cannot be solved, it will have a serious adverse effect on the operation of the water cooler.
Once scaling corrosion occurs in the water cooler, the anti-corrosion coating is accompanied by the silt, microbial slime and impurities often contained in the circulating water. It is easy to produce sedimentation under slow water flow and cause under-scale corrosion under the sediment. Sediments adhere to the inner wall of the tube bundle, causing the cross-section of the circulating water to become smaller and smaller, the flow rate to become slower, and the fluid temperature to become higher and higher, which in turn increases the amount of sediment. As the amount of sediment increases, the flow rate becomes slower and the temperature becomes higher, leading to a vicious cycle until it is blocked.
2. Countermeasures to prevent scaling and corrosion of water coolers
The commonly used descaling methods in the industry are still manual brushing with a wire brush or cleaning with a flexible shaft pipe washer, and the other is to first boil the scale with alkali or acid until it is loose, and then brush it manually. However, these methods are not satisfactory. Not only are they not cleaned thoroughly, but they also have the disadvantages of high cost and labor intensity. In addition, boiling acid will also affect the life of the equipment.
The cleaning of water coolers is mainly divided into cleaning of tube sheets and tube bundles. Tube sheet cleaning is generally done by manually hand-held high-pressure spray guns. The nozzle is aimed at the longitudinal and transverse gaps between the tubes. The scale between the tubes is cleaned longitudinally while the device is moved until the dirt in all the gaps between the tubes is cleaned, thereby completing the cleaning of the water cooler tube sheet. To clean the tube bundle, first remove the head and tail of the heat exchanger to expose all the tubes, then use a rigid spray gun or a flexible high-pressure spray gun to insert the tube hole 200-300mm away, open the spray gun control valve, and pressurize the high-pressure water until it reaches the rated pressure. Then, during the cleaning process, gradually push the spray gun deeper into the pipe until the high-pressure water jet sprays out from the other end of the heat exchanger. After that, the operator slowly withdraws the spray gun in the working state, and the scale continues to be broken until the spray gun is pulled back to the pipe mouth when it was sent in, and the scale is gradually discharged from the pipe. After that, the same method is used to clean each tube until the entire water cooler pipe is cleaned.
Guangyuan Equipment recommends using a 1500bar, 50L/min high-pressure cleaning machine to clean the water cooler tube sheet and tube bundle. The equipment is simple to operate, highly flexible, and can adjust the cleaning pressure during cleaning. It can operate continuously for a long time and is equipped with water shortage protection. During cleaning, the high-pressure water generated by the high-pressure plunger pump is used to convert the huge pressure into a highly energy-concentrated water jet (150MPa) through the nozzle, which cuts and breaks the scale and peels it off from the surface of the object, achieving the purpose of descaling and solving the scaling and blockage problems inside the heat exchanger.
