A new data collection method for evaluating machine condition
- Public Utility District of Grant County, Ephrata, WA (United States)
Profile irregularities have developed on the surface of the discharge ring (liner) of turbines at the Wanapum Dam Development in Washington State during nearly 30 years of operation. Wanapum Dam is part of the Grant County Public Utility District's 1,878-MW Priest Rapids Hydroelectric Project on the Columbia River. The development's ten Kaplan turbines operate under an average 80 feet of head at 85.7 revolutions per minute. In the mid-1980s, Grant County PUD elected to map out the profile irregularities. In the new method applied to units at Wanapum Dam and Priest Rapids developments, eight linear variable differential transformers (LVDTs) were mounted on a unistrut bracket. LVDTs, which develop a linear relationship between position and output voltage, consist of two sets of coils wound around a movable core. When one coil is excited with AC voltage, the output of the second coil is proportional to the position of the movable core. Grant County PUD used a DC power supply with LVDTs that contain microelectronics to convert the DC supply voltage to AC, and to convert the output coils' AC signal to DC. The DC output signal is fed to a brush chart, an instrument that records the data. The bracket holding the LVDTs is mounted to the leading edge of one blade and the trailing edge of the adjacent blade. A wheel mounted on the end of each LVDT rolls over any rough areas of the liner. As the turbine is slowly rotated by hand, the LVDT core moves in and out in proportion to the change in the blade-to-liner gap. Mechanics check the gap with feeler gages at a point on the liner that each LVDT will pass over. This makes data directly readable, and equal to the actual gap. This information is used to evaluate grinding requirements for proper running clearances.
- OSTI ID:
- 6234263
- Journal Information:
- Hydro Review; (United States), Vol. 11:7; ISSN 0884-0385
- Country of Publication:
- United States
- Language:
- English
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