Successful Recovery by Using Stubbing Re-connected the Broken Rotor-Shaft of Darajat 55 MW Power Plant
[PT. Indonesia Power, Indonesia]
Darajat field is one of the largest dry-steam geothermal power plants located in West Java – Indonesia, with total installed capacity of 271 MW. The existing 3 units are 55 MW unit 1 is owned and operated by PLN, the National State Electricity Company of Indonesia, while the unit 2 with capacity of 90 MW, and 121 MW unit 3 are owned and operated initially by Chevron Indonesia, and further transferred to Star Energy Indonesia. Commissioning of unit 3 power plants was July 4, 1994. It has been operating for 24 years. It is up to October 2017, unit 3 is in normal operation. Since November 2017, the operation data shown excessive increase trend vibration on the bearing generator-side. The unit was shut down for inspection. Again, within 2 weeks, in March 2018, the sharp trend increase vibration on the same previous area. It was founded more damages on the rotor-shaft, shaft-bending, cracks on the governor side and generator side, rubbing rotor and stator with the 4th shroud lost from its position. Considering steam take or pay obligation, recovery action as soon as technically possible, was to do removing all crack from the shaft and welded built-up, followed by machining to match with original dimensions. Therefore, while machining removed crack from the shaft, the crack is very deep propagate up to almost the center of the shaft and then rotor shaft was broken down during machining, become two pieces. Option to buy new rotor will take very long time. The broken shaft was then be re-connected by stubbing technique and welded built-up up to the slightly above original diameter, to give clearance for final machining. The point of broken shaft was very close to the last 6th blades, consequently the last blade was removed during re-connected stubbing process of the shaft. After more than 4 months shut down Darajat 1 is now back in operation. So far, the unit rated is 55 MW. Further investigation both operation parameters and power plants efficiency are under monitoring.
|        Topic: Power Generation||Paper Number: 26021|