Reasons and preventive measures for cavitation of circulating water pump impeller

The circulating water pump is one of the important equipment in the circulating cooling water system, and its normal operation is directly related to the synthesis of ammonia and urea in both new and old systems

Long cycle operation of the device. During the operation of the circulating water pump, cavitation is an important hazardous factor affecting the pump outlet flow rate and head.

A certain company's engineering workshop has a total of 13 circulating water pumps for cooling towers 3 #, 4 #, and 5 #. During the annual system overhaul, the pump casing is opened to inspect the impeller, and it is found that there are all 13 circulating water pumps present

Different degrees of cavitation, especially severe cavitation at the suction end of the impeller of the 2201-JA/JB/JC/JD4 circulating water pumps in the 3 # cooling tower

The outer edge is severely corroded and damaged, and there is a large area of ulcerative corrosion and even perforation at the suction end of some impellers;

There is cavitation at the water baffle of the pressure chamber of the pump casing of the 1101-J3/J4/J53 circulating water pumps in the 4 # cooling tower, and some impellers have severe corrosion.

Due to the fact that the impeller and upper and lower pump casings of the circulating water pump are made of cast iron material, what method should be chosen to repair the less corroded impeller and pump casing to improve steam resistance

The ability to corrode and wear, and ensuring good quality, is the key to ensuring the long-term normal operation of circulating water pumps.

Cavitation phenomenon and its hazards

Cavitation phenomenon is a physical characteristic of water and steam changes. When a centrifugal water pump operates normally, the liquid pressure decreases from the pump inlet to the impeller inlet, and at the impeller

Near the inlet of the blade, liquid pressure. When the impeller rotates, the high-speed rotating impeller does work on the liquid, increasing the energy and pressure of the liquid.

When the pressure near the inlet of the impeller blade is less than the saturated vapor pressure at the liquid delivery temperature, the liquid begins to vaporize and produces bubbles, which follow

When the liquid flow enters the high-pressure zone inside the pump body, it ruptures, and the surrounding liquid quickly fills the cavity of the original vapor bubble, generating hydraulic impact, and the generation of this vapor bubble

The phenomenon of development and rupture is called cavitation.

When cavitation occurs, the overcurrent components are subjected to erosion and corrosion damage, resulting in a sudden decrease in pump performance. In severe cases, it can generate noise of 600-25000Hz and unit vibration

The mutual excitation between the two causes a strong cavitation resonance phenomenon in the pump, leading to a major accident of equipment damage.