Tubular heat exchanger in the production, the tube plate and the tube of the general use of manual arc welding, weld shape there are different degrees of defects, such as depression, pores, slag, etc., the distribution of weld stress is not uniform.
When used, the tubesheet section is generally in contact with industrial cooling water, and impurities, salts, gases, and microbes in industrial cooling water can form corrosion to the tubesheet and welds. This is what we often say about electrochemical corrosion. Studies have shown that industrial water, whether fresh or seawater, will have a variety of ions and dissolved oxygen, which chloride ion and oxygen concentration changes, the corrosion of metal plays an important role in the shape. In addition, the complexity of the metal structure will also affect the corrosion pattern. Therefore, the corrosion of the tube plate and the pipe weld is mainly pitting corrosion and crevice corrosion.
From the outside, the tube plate surface will have many corrosion products and accumulation of objects, the distribution of the size of the pit. When the sea water as the medium, but also produce galvanic corrosion. Chemical corrosion is the corrosion of the medium, the heat exchanger tube board contact with a variety of chemical media, will be subject to chemical corrosion. In addition, the heat exchanger tube plate and the heat transfer tube will produce a certain degree of bimetallic corrosion. Some tube plate is also long in the erosion of corrosive media, especially fixed tube plate heat exchanger, as well as temperature stress, tube plate and heat exchanger connection easily leak, resulting in heat exchanger failure.
Source: China Tube Plate Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)