According to the working principle, there are two kinds of cleaning methods: mechanical cleaning and chemical cleaning; According to whether the equipment is running, it can be divided into online cleaning and off-line cleaning. The following first introduces the mechanical cleaning method of the lower heat exchanger, which provides a force greater than the adhesion force of the dirt by the flow of fluid or mechanical action to make the dirt fall off the heat exchange surface. There are two kinds of mechanical cleaning methods: one is the strong cleaning method, such as spray cleaning, steam spraying cleaning, sand blasting cleaning, scraper or drill bit descaling, etc; The other is soft mechanical cleaning, such as wire brush cleaning and rubber ball cleaning. The following are the methods: water spray cleaning, which is a method of scale removal by high pressure water jet or mechanical impact. The water pressure is generally 20-50mpa when this method is adopted. There are also 50-70mpa with higher pressure. Spray steam cleaning, this kind of washer is similar to that of water spray washer in design and operation. This equipment is used to spray steam into the tube side and shell side of the heat exchanger, and the dirt is removed by impact force and heat. Sand blasting is to generate a strong linear velocity by using compressed air (300-350kpa) of screened quartz sand (generally 3-5mm) through the spray gun, scour the inner wall of the heat exchanger, remove the dirt, and restore the original heat exchange characteristics of the pipe. Scraper or drill bit descaling, this cleaning machine only applies to the dirt in the pipe or cylinder. A descaling scraper or drill bit is installed at the top of the flexible rotating shaft, which is rotated by compressed air or electricity (also with hydraulic or steam). The rubber ball cleaning is carried out with shot peening washer. Shot peening washer is composed of sponge ball and fluid spray gun inside the pipe to be cleaned. The ball is shell shaped, and is made of semi rigid foam polyurethane sponge, which is elastic.