Abstract: The result of vacuum leakage test of unit No.3 in a power plant was below standard all the time after its minor repair in January 2009; the decreasing speed of the condenser vacuum in testing basically remained in 600 Pa/min. The leakage of the vacuum system was detected by using the vacuum leak detector, and related leakage points were found. The suggestion for system improvement was put forward. The leakage points were plugged, and the system was improved; so the result of vacuum leakage test of unit No.3 became qualified.

Key words: vacuum leakage test, leakage level, leakage detection, plugging