Self-Cleaning Filters Permit Avista to Use River Water to Cool Compressors

The Cabinet Gorge Dam was doing some retooling a short time ago and they had to make some important decisions on filtering. The dam is the second largest of eight hydroelectric developments operated by Avista, a major electric and gas utility headquartered in Spokane, Washington.

The dam itself is located on the Clark Fork River in Idaho. Its licensed generating capacity is 263.2 megawatts and it features one vertical Kaplan turbine and three vertical propeller turbines. The challenge faced by the engineering team at Cabinet Gorge was to remove three old compressors and replace them with two more efficient compressors with higher flow rates.

“The three compressors were still performing close to their rated flow rates,” said Tracy West, mechanical engineer for Cabinet Gorge. “But there were several reasons to replace them. They were 59 years old and were nearing the end of their service life, parts were difficult to obtain, and the motor inrush currents were high and would likely cause problems in the future.” The functions of the compressors were to provide general shop air to the facility, to serve as an energy source for brakes on each unit, and are used to provide air for forcing all of the water out of a unit when it needs to be turned without any load on it.

“The selection of the new compressors went smoothly,” said West. “The original selection process was done by my predecessor for a similar installation on another dam. The original compressors were reciprocating units. The decision was made to replace them with two 250 horsepower Kobelco screw compressors.