The main factors affecting the corrosion of tube shell heat exchanger

Tube shell type heat exchanger with carbon steel, stainless steel and copper, the carbon steel pipe plate in cooler when in use, the tube plate and the tube seam often corrosion leakage, leakage into the cooling water system caused by environmental pollution and material waste.

In the manufacture of shell and tube heat exchanger, manual arc welding is commonly used in the welding of tube plate and tube plate. The shape of the weld has different defects, such as depression, porosity, slag inclusion and so on. In use, the tube plate is generally in contact with industrial cooling water, and impurities in industrial cooling water, salts, gases, microorganisms, will constitute the corrosion of the pipe plate and weld, which is often said that the electrochemical corrosion. The study shows that the industrial water, whether it is fresh water or sea water, can have all kinds of ions and dissolved oxygen, which changes the concentration of chloride and oxygen, which plays an important role in the corrosion of metal. In addition, the complexity of the metal structure will also affect the corrosion morphology. Therefore, pitting corrosion and crevice corrosion are the main corrosion of tube sheet and tube weld. From the outside, there will be a lot of corrosion products and products of the surface of the tube plate, the distribution of the size of the pit. By using sea water as medium, can generate galvanic corrosion. Chemical corrosion is the medium of corrosion, heat exchanger tube plate contact with a wide variety of chemical media, will be the corrosion of chemical media. In addition, the heat exchanger tube plate and the heat exchange tube will produce a certain double metal corrosion.

In summary, the main factors that affect the corrosion of shell and tube heat exchanger are:

1. Medium composition and concentration: the concentration of different, for example, in hydrochloric acid, the greater the general concentration of the more severe corrosion. Carbon steel and stainless steel in the concentration of 50% sulfuric acid in the most serious corrosion, and when the concentration increased to more than 60%, but the sharp decline in corrosion;

2. Impurities: harmful impurities, including chloride ions, sulfur ions, cyanide ions, ammonia ions, etc., these impurities in some cases will cause serious corrosion

3. Temperature: corrosion is a chemical reaction, the temperature of each increase of 10 degrees Celsius, corrosion rate of about 1~3 times, but there are exceptions;

4. PH value: the smaller the average pH value, the greater the corrosion of metals;

5. Flow rate: in the majority of cases, the greater the flow rate, the greater the corrosion.