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We have an Alstom 620MW, 689MVA, 20kV generator on our power station. We are experiencing the following challenges:
1. High hydrogen seal oil flow; about 220l/min whereas we used to run at 90l/min in the past and on all other units. The oil flow rate is about 90 - 110 l/min on barring, as opposed to 20l/min in the past.
2. Our seal oil vacuum compartment runs empty when we run the turbine up. This cavitates the AC main seal oil pump, but we miraculously keep the turbine from tripping on low differential pressure by switching on the emergency DC pump.
3. So we have a situation were now we keep the generator on load by running the AC and DC pump. The discharge pressure on the AC pump is about 1400 kPa as opposed to 900 kPa under normal conditions.
4. The Hydrogen/seal oil differential pressure is unstable and fluctuates around 30kPa as opposed to being stable at 50 kPa.
We suspected that the hydrogen seals are damaged and shut the unit down for repairs. We replaced the seals and the seal springs and came back with the same issues. We have turned the seal oil plant upside down but still can point to the source of the problem.
Has anyone experienced this problems and how did you sort them out? Can anyone help with a proper diagnosis or lead me to a source that can help?
1. High hydrogen seal oil flow; about 220l/min whereas we used to run at 90l/min in the past and on all other units. The oil flow rate is about 90 - 110 l/min on barring, as opposed to 20l/min in the past.
2. Our seal oil vacuum compartment runs empty when we run the turbine up. This cavitates the AC main seal oil pump, but we miraculously keep the turbine from tripping on low differential pressure by switching on the emergency DC pump.
3. So we have a situation were now we keep the generator on load by running the AC and DC pump. The discharge pressure on the AC pump is about 1400 kPa as opposed to 900 kPa under normal conditions.
4. The Hydrogen/seal oil differential pressure is unstable and fluctuates around 30kPa as opposed to being stable at 50 kPa.
We suspected that the hydrogen seals are damaged and shut the unit down for repairs. We replaced the seals and the seal springs and came back with the same issues. We have turned the seal oil plant upside down but still can point to the source of the problem.
Has anyone experienced this problems and how did you sort them out? Can anyone help with a proper diagnosis or lead me to a source that can help?