Text Box: D_Aire: Dissolved Air Tester
How it Works

Product and Process Engineering Concepts

Phone: 208-392-4785

Fax: 888-813-5939

Email: sales@papec.com

D_Air Tester

Measures dissolved air in process fluids


High Vacuum Valve. This valve is designed to seal the tester at the high vacuum developed during testing



Sample Control Valve. This three-way stopcock is used to control addition and removal of sample fluid from the tester.



Sight Glass. During the testing process, dissolved gas is released from solution and converted to a separate gas phase. The gas collects at the top of the calibrated sight glass. The volume of the gas is read in the calibrated sight glass and that volume provides the amount of dissolved gas that was present in the fluid before the high vacuum was applied.










Bellows. As the Bellows is expanded, a high vacuum is applied to the isolated liquid sample. The high vacuum causes dissolved gas to come out of solution into a separate gas phase. Note that in the Figure, the Bellows is in the fully compressed position.




Bottom Plate



Thumb Screw. The Thumb Screw is used to expand and contract the Bellows.




A fresh sample of process fluid is added to the tester through the Sample Control Valve. This is done by connecting one leg of the three-way valve to the process fluid by means of a flexible rubber tube provided by the user. Starting with the High Vacuum Valve in the open position and Bellows in the fully compressed position (as shown in the Figure), the Bellows is expanded to fill the Sight Glass and the internal volume in the Bellows. The process fluid is then pushed back out of the Bellows and Sight Glass by compressing the Bellows, and with the fluid flow directed to the other, discharge, leg of the Sample Control Valve. The process is repeated several times to displace the old sample and replace it with fresh sample.


Then with the Bellows fully compressed, the High Vacuum Valve is closed, and the Bellows is expanded to the extended position. The tester is shaken briskly for 30 seconds to force the supersaturated dissolved air to release from solution and then  Bellows is moved back to the compressed position. The dissolved gas that was released when the Bellows was in the expanded position rises to the top of the fluid that is returning to the Sight Glass.  The volume percent of dissolved gas is obtained by counting the divisions on the Sight Glass that define the size of the gas bubble and then multiplying that number by the appropriate conversion factors.