In the knowledge system related to Han Yu boilers, there are some key points worthy of our in-depth exploration. The following mainly provides answers to some specific questions, which are focused on: The manholes and handholes in the furnace body of Han Yu boilers, what exactly do they refer to? In addition, how should we understand the low-temperature and high-temperature corrosion phenomena that occur during the operation of Han Yu boilers? Since they are all closely related to Han Yu boilers, let’s seriously embark on the learning journey.
1.The manholes and handholes in the furnace body of Han Yu boilers
In Han Yu boilers, manholes have specific uses and definitions. It refers to a passage established in the relevant structure of the boiler, similar to that in the sewer scene, allowing operators to enter and exit, and then carry out a series of key operations such as maintenance. Relying on this manhole, maintenance personnel can smoothly enter and exit important facilities such as the exhaust duct, the main body of the boiler, and the sewer pipe. And the handhole can be popularly understood as a reduced version of the manhole. The original intention of installing the handhole is to facilitate the daily operation and maintenance of the boiler, and to facilitate the staff to carry out various internal works such as the installation and disassembly of components, internal cleaning, and maintenance in case of emergencies. It can be regarded as a considerate device that helps the stable operation and maintenance of the boiler.
These two types of holes are basically the same in structure, both composed of short cylinder sections and blind plates. From the perspective of diameter size, the diameter range of handholes is approximately between 150 – 200mm, and the common nominal diameters are DN150 and DN250. In contrast, the diameter of manholes is much larger, usually above 1000mm.
2.Low-temperature and high-temperature corrosion of Han Yu boilers
Low-temperature corrosion of Han Yu boilers: On the tail heating surface of Han Yu boilers, in key parts such as economizers and air preheaters, if there are substances such as sulfuric acid in the environment, sulfuric acid will combine with water vapor, thereby generating sulfuric acid vapor. When the temperature in the area is not high, sulfuric acid vapor is very easy to condense on the heating surface, and thus, sulfuric acid corrosion occurs quietly. This is what we call low-temperature corrosion. This low-temperature corrosion phenomenon mainly occurs on the air preheater, but the economizer is occasionally “invaded” by it.
High-temperature corrosion of Han Yu boilers: When Han Yu boilers are in a high-temperature operating state, alkali metals will sublime, and then chemically react with sulfur trioxide in the flue gas, and then generate complex sulfates. These complex sulfates are corrosive and will cause erosion and damage to the tubes and tube walls of the boiler heating surface. Since this type of corrosion is induced in a high-temperature environment, it is named high-temperature corrosion. It should be particularly noted that high-temperature corrosion generally occurs repeatedly. If it is not detected and dealt with in time, the tube wall will gradually become thinner. In severe cases, it may even cause dangerous situations such as tube explosion, posing a huge threat to the safe operation of the boiler.
