The author introduced a German first in March 2003. Manroland UNISET75 high speed rotating newspaper The printing line uses the more advanced shaftless drive technology. The core component of the shaftless drive technology is the variable frequency drive, which generates a lot of heat during operation, affecting the function and service life of the production line. In order to make the variable frequency drive better heat and cool, Manroland installed the variable frequency drive in a relatively closed electrical cabinet and used a cooling water system to cool the electrical cabinet where the variable frequency drive is located. However, after using for a period of time, the author found that water leakage often appeared on the heat exchange sheet of the electrical cabinet, and the heat dissipation and cooling of the variable frequency drive could not be performed well. Based on years of experience, the author has modified the cooling water system and shared the experience with the reader.
Transformation of the former
At the beginning of the Manroland UNISET75 high-speed rotary newspaper printing production line, the author assembled the cooling water system according to the technical specifications of the cooling water system. The structure is shown in Figure 1. Taking into account the climatic characteristics of Nanjing, the cooling water system selects the cooling method combining the refrigeration unit and the air cooling unit. In summer and autumn, refrigeration units are used for refrigeration; in spring and winter, air-cooled units are used for cooling. This is because air-cooled units have lower power consumption than refrigeration units, which can save a lot of electric energy and avoid the problem that winter refrigeration units are not easy to start. . In addition, a water storage tank with a capacity of 5 cubic meters is provided in the cooling water system to provide a relatively constant temperature of cooling water to the equipment pumping station.
After more than one year of operation, the author found that water leakage often appeared on the heat exchange sheets of the electrical cabinets. At first, it was thought that the humidity was high in summer, and the air flowed through the relatively cold heat exchange sheets, but the air was relatively dry. Water seepage will still occur in winter, and the situation is getting worse. To this end, the author opened the protective cover of the heat exchange sheet and found that water droplets appeared on the copper tube of the heat exchange sheet through which the cold water passed, so it was initially confirmed that the heat exchange sheet itself leaked, rather than condensation.
In order to further ascertain the cause of water seepage in the heat exchange sheet, the author tested the water quality in the cooling water system. The test results showed that the particulate matter in the water exceeded the standard. The reason is mainly because the pipeline of the cooling water system is too long, and because the floating ball type water supply valve is installed in the water storage tank, and a maintenance port is left above the cooling water system, the cooling water system is in a relatively open state, and a large amount of air enters. The cooling water system causes oxidation and corrosion of the pipeline. A large amount of rust is peeled off from the pipe wall, and as the water flows into the heat exchange sheet of the electric cabinet, the copper tube of the heat exchange sheet is washed and ground. Over time, the wall of the copper tube becomes thinner and eventually wears out, causing water leakage.
After the cause is ascertained, the author moves the floating ball type water supply valve in the water storage tank and seals the inspection port to make the whole cooling water system in a relatively closed state. At the same time, the water quality detection is strengthened, and the cooling water is regularly replaced. . After adopting the above measures, the water leakage phenomenon of the heat exchange sheets of the electrical cabinet is obviously alleviated.
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