Few days back intermittent vibration peaks were observed on a turbine at our plant. The turbine has a history of this kind of stuff going on it for a while. After the overhauling the turbine acts okay but after one or two years of continuous service the vibration peaks are observed. Previous overhauling reports revealed a history of burned oil deposits on the oil seal of the Governor end bearing.
After thorough research it was hypothesized that the peaks were due to the continuous development of burned oil deposits on the oil seal area. When the oil deposits' thickness equals the clearance available, the rubbing between of oil deposits with seal occurs and consequently the vibration increases and as the oil deposits are cleaned by the sharp labyrinths ends of the oil seals, the vibration disappears.
The burnt oil deposits can only be formed if heat (from the steam chest), air (from the vent of steam seals) and oil (from the bearing) are available at the oil seal area.
To avoid the phenomenon of oil deposits phenomenon certain steps were taken:
- first of all an ejector was installed on the other end of the bearing to increase the amount of vacuum in the bearing housing so as to reduce the staying time of the oil in the oil seal.
- Secondly the oil seal was provided with a nitrogen insertion point so as to remove the availability of air
- Thirdly the oil seal oil drain holes were enlarged to remove any oil that may stay in the oil seal. this coupled with the ejector will ensure quick removal of oil from the oil seal.
The turbine was started and the peaks have not been observed for a while.
After thorough research it was hypothesized that the peaks were due to the continuous development of burned oil deposits on the oil seal area. When the oil deposits' thickness equals the clearance available, the rubbing between of oil deposits with seal occurs and consequently the vibration increases and as the oil deposits are cleaned by the sharp labyrinths ends of the oil seals, the vibration disappears.
The burnt oil deposits can only be formed if heat (from the steam chest), air (from the vent of steam seals) and oil (from the bearing) are available at the oil seal area.
To avoid the phenomenon of oil deposits phenomenon certain steps were taken:
- first of all an ejector was installed on the other end of the bearing to increase the amount of vacuum in the bearing housing so as to reduce the staying time of the oil in the oil seal.
- Secondly the oil seal was provided with a nitrogen insertion point so as to remove the availability of air
- Thirdly the oil seal oil drain holes were enlarged to remove any oil that may stay in the oil seal. this coupled with the ejector will ensure quick removal of oil from the oil seal.
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