1. The indirect electric hot water boiler does not control the amount of recharge water. Article 100 of the safety supervision procedures for hot water boilers stipulates: “The leakage of hot water system is generally not more than 1% of the water capacity of the system”, but some units mistakenly believe that with hot water boilers, it is convenient to use hot water. The hot water is used for bathing, washing clothes, etc., a 2.8 MW hot water boiler, which replenishes nearly 100 tons of water every day.
2. Do not conscientiously implement the “Low Pressure Boiler Water Quality Standard” (hereinafter referred to as the standard). The standard clearly stipulates that when the water supply temperature is ≤95 °C, the circulating water should control the PH value to 10-12, which is a very important indicator, but some units are not implemented. These units pay more attention to the hardness of the make-up water. Some also deliberately installed the fluidized bed water treatment to meet the need of supplementing the softened water. They mistakenly supply the hot water boiler according to the steam boiler water standard, and think that the softened water is qualified, so Will foul and corrode.
3. The installation of the hot network pipeline is unqualified, and the circulating water is not delivered to the user at the end of the system. Some users increase the number of air discharges in order not to freeze, and the drainage is hot, and the heat is not discharged, resulting in an increase in leakage.
4. The expansion tank is inconsistent with the constant pressure of the boiler. The expansion tank of a unit is located on the fourth floor, its height is less than 15 meters, but the constant pressure of the boiler is 2.5kg/cm2. As a result, the furnace worker maintains the working pressure index of 2.5kg/cm2 and often replenishes the water. The white ground overflows into the ditch, which means that it costs water and costs coal.
5. Indirect electric hot water boiler shutdown is not maintained. After the heating period, the boiler was shut down, temporary workers were dismissed, some boilers were filled with softened water, and some boilers were exposed to the atmosphere, lacking the necessary maintenance.
The above situation can clearly show that the corrosion of hot water boilers is caused by the lack of knowledge of hot water heating by users, especially the large amount of water supplementing, which not only supplements a large amount of dissolved oxygen, but also because of the large amount of water. The processing equipment is overloaded, and the water with a high content of chloride which is not qualified for flushing is often added to the system to ensure the amount of water replenishment. In the case where the pH of the furnace water is only 7-8, hydrogen ions, oxygen ions, chlorine Ions and the like are very active as corrosive media. Since the pH of the furnace water is low and the hydrogen ion concentration is high, the hydrogen will undergo a cathodic reaction under the ulcer corrosion. When there is dissolved oxygen in the water, the presence of chloride will greatly increase the corrosion rate of iron. The ions are easily adsorbed by the oxide film on the metal surface and replace the oxygen ions in the oxide film, thereby forming soluble chloride, destroying the oxide film, and continuing the corrosion of the metal surface. Based on the above, it is known that excessive supply of water to the hot water heating system is the key to causing corrosion and lowering the service life of the hot water boiler.
The ideal indirect electric hot water boiler operating system should be basically tight and not leaking. There is a fixed amount of water circulating in the system, and the process of endothermic heat release is carried out. After the water is recycled, the dissolved oxygen in it is completely absorbed by the iron, and becomes an oxygen-free water, which will not cause serious corrosion to the boiler. It is reasonable to require that the leak rate in the hot water boiler regulations not exceed 1% of the system's water capacity. To prevent corrosion of hot water boilers, the following are recommended:
1. For boilers with excessive water supply rate, it is necessary to find out the cause and cure the disease, cut off all the water drainers, block all run, run, drip and leak, increase the system automatic air release valve, strictly manage the system, and make the water supply rate reach the standard. .
2. A small amount of supplementary water is inevitable, but the quality of the make-up water should be emphasized, and Zui is good to supply deoxygenated water. The boiler water used for heating alone can use the residual heat of the tail flue. Preheat the cold water (soft water) to 70 ° C - 80 ° C, and then add the appropriate amount of trisodium phosphate and sodium sulfite into the boiler at the same time, which is beneficial to the boiler. It is harmless.
3. Strictly control the pH value of the boiler water. It is necessary to check the PH value at regular (two hours). When the pH value is lower than 10, the dosage of trisodium phosphate and sodium hydroxide can be increased to adjust.
4. Make maintenance of the shutdown. There are two kinds of dry method and wet method. If the furnace is shut down for more than one month, the dry maintenance method should be adopted. The wet maintenance method can be used for one month or less after the furnace is shut down. After the hot water boiler is deactivated, the Zui should be cleaned by dry method. The water should be drained, and the moisture should be dried out with a small fire. Then add the raw stone or calcium chloride, and add 2 kg to 3 kg per cubic meter of boiler volume. Make sure the inner wall of the pan is dry, which will effectively prevent corrosion during deactivation.
5. After every 3-6 months of operation of the hot water boiler, the furnace should be shut down for comprehensive inspection and maintenance.