Crack Analysis of Water Cooling Tubes of 125,000 KW Double Water Internal Cooling Turbine Generator

Analysis of Fracture of Water Cooling Pipe for 12.5MW Double Water In-Cooled Steam Turbine Generator

The 12.5MW double water in-cooled steam turbine generator is a large-scale set of power generating units, which helps to generate electricity. During its operation process, stress concentration problems often arise and lead to cracking or fracture of the water cooling pipe. This paper will analyze the fracture causes of the 12.5MW double water in-cooled steam turbine generator water cooling pipe.

To begin with, poor design of the water cooling pipe may be the cause of its fracture. The cooling water system of a steam turbine generator is a very important part, and its design and material selection will determine the performance of the equipment. If the design parameters are not properly calculated, resulting in a cooling pipe of a certain thickness, material, or length, it is easy for the water cooling pipe to cause cracking and leakage.

In addition, the tapping process of the water cooling pipe can also lead to its fracture. In the process of manufacturing the water cooling pipe, it is necessary to blow, forge and tap. At this time, if the tapping process is not done properly, it will cause stress concentration, resulting in cracking and fracture of the pipe.

Moreover, the appearance of corrosion is also the most common condition for fracture of the water cooling pipe. Generally, the fracture occurred at the corrosion area of the pipe. This is due to the fact that the corrosion of the pipe wall leads to the thinning of the pipe wall, thereby reducing its ability to bear the internal pressure and leading to cracking or fracture.

In addition, it is also possible that improper maintenance may lead to fracture of the water cooling pipe. The water cooling pipe will be blocked due to the smudging of scale, thereby reducing its water flow rate and pressure, resulting in cracking. At this time, if timely cleaning and maintenance are not carried out, it will cause the water cooling pipe to burst.

Therefore, in the process of using the 12.5MW double water in-cooled steam turbine generator, attention should be paid to the use of water cooling pipe. At the same time, the water cooling pipe should be maintained regularly to prevent its cracking and leakage. In addition, it is necessary to detect the strength of the water cooling pipe at regular intervals to prevent the occurrence of fracture.

Analysis of the Fracture of Water Cooling Pipe of 12.5 MW Double Water Internal Cooling Steam Turbine Generator

Background: On the afternoon of April 25, 2017, a 12.5 MW double-water internal cooling steam turbine generator produced by a well-known company was put into operation. On April 27, it was found that the cooling water pipe connected to the generator bearing was broken. After repeated testing and analysis, it was determined that the water cooling pipe of the steam turbine generator was broken and affected its operation.

Fracture Cause Analysis:

1.The design of the water-cooling pipe: The water-cooling pipe used in the steam turbine generator is a double-tube structure. The inner sleeve of the pipe is a stainless steel pipe, the outer sleeve of the pipe is a carbon steel pipe, and the cooling medium passes through the inner stainless steel pipe. Through the analysis of relevant drawings, it was found that the material used in the production of this double-tube structure water cooling pipe was inappropriate.

2. Water quality of the cooling system: Increase of solid particles, oil and other substances in the cooling water system may increase the wear of main components in the system, and even cause blockage in some cases, which can easily lead to excessive pressure in the water-cooling system of the steam turbine generator.

3.Machine vibration: Excessive vibration of the steam turbine generator caused by insufficient seismic design of the machine foundation can cause the water-cooling pipe and its connecting parts to rub against each other to form a local stress concentration and even crack under strong loads.

Conclusion: After the above analysis, it is determined that the main reason for the fracture of the water cooling pipe of the 12.5 MW double water internal cooling steam turbine generator is the material design of the pipe structure is not suitable. In subsequent operation, it is necessary to check the water quality of the cooling system regularly and take relevant measures to reduce the vibration of the machine.