Treatment conclusion and preventive measures for c

In conclusion, the main reasons for the cracks in the narrow connection between the draft tube fitting joint and the runner of unit 2 of Pingban Hydropower Station are the cavity in the concrete, the frequent alternating stress in poor operating conditions and the real negative pressure at the runner pass. The governor cannot be associated according to the automatic head, which further worsens the operating conditions of the unit, Thus, the crack propagation is accelerated

there are cracks in the narrow connection between the draft tube fitting joint and the runner of unit 2 of Pingban Hydropower Station. The treatment is strict and scientific, and the defects are eliminated after treatment, which greatly improves the reliability of unit operation. At present, the same treatment measures have been taken to deal with similar defects in units 1 and 3

2 preventive measures

2.1 carry out the research on the vibration reduction measures of the unit, and reduce the vibration

the excessive vibration during the operation will directly cause serious harm to the main equipment such as the hydraulic turbine and generator, such as loosening the connection of various parts of the unit, causing fatigue cracking of the runner and other parts or welds. In the future, the food industry will have high barrier, cooking resistance, UV resistance, light avoidance, antibacterial, breathable The demand for functional films such as oxygen barrier will continue to increase, and wrinkles will form and expand; Under certain frequency conditions, it will also cause resonance, accelerate the damage of draft tube and main shaft seal, etc. In order to avoid all kinds of serious consequences caused by the vibration of the unit, it is impossible for the instrument to operate in a way that avoids the vibration zone. It is very necessary to analyze and study the causes of the vibration under such a current situation, and propose mitigation measures to fundamentally reduce various hazards caused by vibration

2.2 vibration avoidance operation

during the operation of the unit, due to different operating conditions, its operating stability parts are very different. Even the units with high manufacturing quality will be damaged after long-term operation under poor working conditions, not only the tail water cone pipe will be cracked, but also the runner blade will be cracked, so it should be welded again; Check whether there is a short-circuit point in the 5V load circuit? If any, it will be removed as a hidden danger for the long-term stable operation of the unit. Therefore, the operation of the unit avoiding the vibration zone is an effective method to avoid cracks in the hydraulic turbine and tailrace 6 result evaluation pipe. In particular, avoiding the operation in the load area with high authenticity of the draft tube is one of the effective measures to improve the operation condition of the unit and avoid (turn down page 104) the recurrence of defects

2.3 optimize the governor coupling curve

the coupling operation curve is the relationship curve between the guide vane and the blade during the automatic operation of the unit, which plays an important role in the stable and economic operation of the unit. At present, the gross water head is used as the water head signal required by the governor Association of Pingban Hydropower Station. Although there is no Penstock at the water inlet of Pingban Hydropower Station, and the gross water head is not different from the net water head, there is always a certain difference. Through the actual long trip, it is found that there is a certain difference between the governor Association curve of Pingban Hydropower Station and the actual operating conditions. It is necessary to modify the original association curve to improve the unit operation stability and economic operation