Method and apparatus for detection of vacuum leak

A method for detecting a leak of a vacuum vessel in which water used as refrigerant and a solution used as working fluid are charged, comprising the steps of:

• purging a gas in the vacuum vessel by an air pump via a dehumidifier while spraying a helium gas to the outer surface of the vacuum vessel;
• leading the purged gas from which water vapor has been removed by the dehumidifier to enhance the detectability of the helium gas from the suction side of the air pump;
• regulating a pressure of the dehumidified gas in accordance with a power of the dehumidifier by a pressure regulating valve, and
• detecting the helium gas in the dehumidified gas by a mass spectrometer-based helium leak detector.

A method for detecting a leak from a vacuum vessel in which water used as refrigerant and a solution used as working fluid are charged, comprising the steps of:

• purging a gas in the vacuum vessel by an air pump via a first dehumidifier while spraying a helium gas to the outer surface of the vacuum vessel;
• diverting a part of the purged gas from which most of the water vapor is removed when passed through the first dehumidifier and which flows into the air pump by a branch pipe provided in a purge piping;
• passing the diverted purged gas through a second dehumidifier to remove the rest of water vapor contaminated in the gas;
• adjusting a pressure of the purged gas at an inflow side of the second dehumidifier so as to match the operating conditions (power) of the first and second dehumidifiers, and
• detecting the helium gas in the dehumidified gas by a mass spectrometer-based helium leak detector.

A vacuum leak detecting apparatus with a mass spectrometer based helium leak detector for detecting a leak from a vacuum vessel provided in an absorption refrigerator and in which water used as refrigerant and a solution used as working fluid are charged, comprising:

• first pumping means provided in a purge pipe which is to be connected to the vacuum vessel for purging a gas in the vacuum vessel;
• a dehumidifier connected to the purge pipe at a suction side of the first pumping means for removing water vapor contained in the purged gas;
• first and second valve means, both disposed at an outlet of the dehumidifier in series in the purge pipe;
• second pumping means disposed between the first and second valve means for a further evacuation of the purged gas;
• a turbo-molecular pump connected at the back pressure side thereof to a delivery side of the second valve means and at the high vacuum side thereof to a mass spectrometer tube of a helium leak detector;
• first pressure sensing means for detecting a pressure of the purged gas at the outlet of the dehumidifier and delivering an output signal corresponding to the pressure;
• second pressure sensing means for detecting a pressure of the purged gas at the back pressure side of the turbo-molecular pump and delivering an output signal corresponding to the pressure, and
• an automatic controller to regulate the opening/closing of the first and second valve means and to control the start/stop of the turbo-molecular pump, based on the output signals from the first and second pressure sensing means.