What are the reasons for the breakdown of the impeller in the turbine condensate pump?
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The turbine condensate pump has been suffering from cavitation during operation; it required major repairs twice over three years, and in each case it was the inducer that was damaged. The parameters of this water pump are as follows. Model: 6N6, Speed: 2970, Temperature: 53 degrees Celsius. As shown in the image: the induction wheel that has been broken down. 1 We suspect that the liquid in the rehydrator contains air bubbles, which enter the pump along with the liquid, causing abnormal noises at the volute and leading to the breakdown of the impeller. Please analyze why this is the case Thank you!
The reason for the breakdown of the impeller in steam turbine condensate pumps is cavitation. It should be noted that the \"gas\" involved in cavitation does not refer to air mixed in the condensate water. Cavitation occurs when the flow velocity of the fluid increases, resulting in a local decrease in pressure. When this local pressure drops below the critical value, bubbles form within the fluid. When the pressure rises again, these bubbles burst explosively – this is what constitutes cavitation. The destructive effects of cavitation can be quite severe; you can find more detailed information on this topic by searching this forum.
The installation height of the condensate pump is inappropriate – it might be too high. The pressure at the condensate inlet is low, and there is air inside the pump. By lowering the installation height of the pump appropriately, the inlet pressure can be increased, thereby enhancing the pump’s resistance to cavitation. Additionally, an air pipe can be installed at the inlet of the condensate pump to allow any air present inside the pump to be discharged into the condenser, thus improving the working conditions of the pump.
The impeller was damaged due to cavitation.
The installation height of the condensate pump is not appropriate – it might be too high. The pressure at the condensate inlet is low, and there is air inside the pump. By lowering the pump’s installation height appropriately, the inlet pressure can be increased, thereby enhancing the pump’s resistance to cavitation. Additionally, an air pipe can be installed at the inlet of the condensate pump to allow any air present in the pump to be discharged into the condenser at all times... This pump has an air pipe at its inlet line that is connected to the condenser; the main noise comes from the inlet impeller. After several attempts to inspect and repair it, it was found that the impeller was damaged. Could it be that the valve on the air pipe at the inlet is set too wide? Should it be turned off after the pump starts normally? Please give some advice
This cavitation may be due to system-related issues on the one hand, or it could also be because the material of the pump impeller is of very poor quality. Circulation pumps are prone to cavitation in their operating environment, and combined with poor impeller materials, they fail quite quickly. It is recommended to apply a composite material coating for protection of the impeller. Composites possess good toughness; compared to relatively rigid materials, they also have decent resistance to cavitation.
Our unit also uses 6N6 condensate pumps; however, there has been no occurrence of breakdown of the impeller due to induction wheel effects. Undoubtedly, cavitation is the cause of impeller breakdown
Cavitation is mainly caused by insufficient suction height
Cavitation is caused by the poor quality of the material used for the impeller; the pumps in our unit suffered from severe cavitation problems due to issues with the impeller material, and eventually had to be sent back to the manufacturer
Thank you all for your responses. Unfortunately, I’m unable to give you any scores, so I’ll have to ask the moderator of this forum to handle it. This pump needs to be overhauled once a year, and its impeller is made of brass. Is it possible to change the material, for example to stainless steel? Please share your opinions!
1. If the suction height is insufficient, the liquid level can be increased appropriately to raise the suction pressure； 2. Check whether the inlet filter is clogged, which may affect the suction pressure ； 3 Material inspection.