Application characteristics of ultra-high pressure water jet cleaning

　　Ultra-high pressure cleaning equipment is characterized by no damage to the metal surface, no additives, power plant condenser steel pipes, good results in cleaning boiler tubes and rotary air preheaters

　　1) Water is a flexible substance. During cleaning process, water is atomized first, and its quality is small. Although there is a high pressure and a fast flow rate, it will not damage metal surface and will not damage protective film on metal surface.

　　2) The cleaning process is completely carried out with clean water without adding any additives, and there is no environmental pollution and waste disposal.

　　3) Working environment of cleaning process is improved, and labor intensity is low. Suitable for working in flammable and explosive places.

　　4) Cleaning quality is better and cleaning coverage is wider.

　　See Figure 1 for the condition of steam turbine blades after being cleaned by ultra-high pressure water: The steam turbine has been in operation for many years, and has not been sandblasted before, and metal color appears after cleaning. It can be seen from the figure that metal protective film has not been damaged, and metal surface is as smooth as new.

　　See Figure 2 for the condition of lower half of steam turbine rotor after being cleaned with ultra-high pressure water: the steam turbine has been in operation for more than ten years, and has been subjected to sandblasting for many times before. Although original color of metal appears after cleaning, it can be seen from Figure 2 that metal surface is obviously rough and not smooth, leaving traces after sandblasting. The economy of unit operation is also affected at the same time.

　　Ultra-high pressure water cleaning technology has relatively high requirements for both equipment and operation: this equipment includes two parts: the host and accessories. The following are the main performance parameters of the host:

　　Maximum pressure: 3000 MPa

　　Pressure adjustable range: 2200 ~ 3 000 MPa

　　Maximum flow rate: 19 L/min

　　Generally, the cleaning pressure is controlled at about 260 MPa, and the effective cleaning spray distance is about 12 cm.

　　The accessories are mainly composed of three parts: high-pressure delivery pipe, cleaning handgun and nozzle. The key technology is that the cleaning handgun is equipped with a power that can make the nozzle rotate at a high speed, and its maximum speed of the nozzle can reach 3000 r/min. The nozzle is composed of two parts, nozzle holder and nozzle, and diameter of nozzle is only 0.3 ~ 0.4 mm. The rotation of nozzle mainly has several functions: one is to atomize the high-pressure water ejected from nozzle; the other is to minimize residence time of jet on the surface of object to be cleaned during cleaning process. In addition, the cleaning is mainly to use the pressure to convert flow rate of work carrier water. The atomized water particles are very small, quality is also small, and water is a flexible substance. Under the premise of cleaning, the waterpower distribution is more uniform and guaranteed does not damage the base material being cleaned.

　　Ultra-high pressure water cleaning is widely used in power plants, as far as the author personal experience includes power plant condenser tube, boiler tube and rotary, cleaning of air preheater, ash discharge pipe and high temperature superheater, etc. very good results have been achieved.