Oxygen corrosion causes and prevention of low pressure hot water boiler




The low pressure hot water boiler responsible for heating, circulating water for 24 hours in a row, the general heating period is 8 months. In the pipe network and internal circulation of the low pressure hot water boiler, the boiler water can not avoid contact with the pressed metal original, which will cause serious corrosion. The boiler is cooled by the drying method. The water quality is tested by the high quality water treatment tester. The boiler is equipped with softened water treatment and the water quality index is recorded every two hours. If the influent liquid level is not up to the normal water level after a period of use, there is water leakage, and a large amount of scale and black residue are found in the boiler discharge. The surface of the pipe of the boiler is covered with brown powdery substance, and most of the analysis is iron oxide. After cleaning, many pit-like etch pits were found, with a depth of about 3 mm. It can be judged as oxygen corrosion by the above phenomenon.
The chemical reaction process of oxygen corrosion in low pressure hot water boilers is: electrochemical corrosion of iron when it is corroded by oxygen in water. Cathodic Process Oxygen is a strong cathode de-leveling agent that absorbs cathode electrons to form fluoride-oxygen ions. The chemical reaction intensified by the corrosion process is an anodic process, the electrode potential of the iron is lower than the electrode potential of the fluorine, and the cathode reaction product reacts with the anode reaction product to form rust.
During the operation of the boiler, the heating system pipe network is aging, and the leakage system is not tight, which is easy to cause oxygen corrosion, effectively strengthen the inspection and management of the pipe network, and avoid rabbit dripping. Boiler water PH value is 5-9, oxygen ions, etc. are active as corrosive media. Because oxygen is a de-leveling agent, its depolarization occurs at the anode and produces rust. Therefore, excessive hot water heating system replenishes water, which is the key to causing boiler corrosion to reduce service life. When the boiler is in normal operation, the pH value of the pot water is controlled within the range of 10-12, which can form a protective film on the metal surface, thereby reducing the corrosion rate of the boiler. Corrosion of boilers during outages is more severe than corrosion during operation. Large-scale corrosion damage and localized corrosion are often caused by outage corrosion. Therefore, it is especially important to maintain the boiler during the four-month shutdown of the boiler. The boiler water is released, the boiler flue door is opened, the scale ash is removed, and the cleaning is thoroughly cleaned. According to the furnace volume calculation, the desiccant dosage is used, and the desiccant is regularly checked. 
Low pressure hot water boilers also have to do a good job in corrosion prevention. First of all, we must strengthen management and supervise the strictness of the pipe network to prevent leakage. Secondly, it is necessary to strengthen the detection of water quality, and the pH value can be controlled within a reasonable range to achieve the purpose of reducing oxygen corrosion. In addition, the boiler shutdown maintenance should be done well, which is very important to prevent corrosion and prevent accidents.
The quality of the low pressure hot water boiler directly affects the degree of corrosion of the boiler and the normal operation of the boiler. In order to prevent corrosion accidents in low pressure hot water boilers, it is necessary to reduce the oxygen corrosion of boiler water.
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