Text Box: D_GR: Dissolved and Entrained Air Tester
How it Works

Product and Process Engineering Concepts

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The D_GR is a piston and cylinder apparatus for determining dissolved and entrained gas content of a liquid. It consists of two axially-aligned cylinders, one a small diameter sample cylinder and the other a large diameter vacuum cylinder.  A vacuum piston is contained in the vacuum cylinder and a compression piston of diameter less than the sample cylinder is axially placed within the vacuum piston. The initial configuration places the compression piston fully retracted into the vacuum piston, and the vacuum piston fully extended against the end of the sample cylinder so that the vacuum cylinder has no volume. Liquid sample flows through the sample cylinder. Closure of the feed and overflow valves isolates a liquid sample in the sample cylinder. The compression piston is then advanced into the sample cylinder to compress any air entrained in the liquid sample. The resulting pressure increase and volume change are  used to calculate the entrained air content. The compression piston is then retracted and the vacuum piston is retracted to open up the large vacuum cylinder and to place the liquid sample under high vacuum with the liquid resting as a thin layer on the top of the vacuum piston. This action rapidly releases dissolved air. The vacuum piston is returned to the extended position to close the vacuum cylinder and the liquid sample is compressed just as it was for the entrained air measurement in order to determine the additional amount of released dissolved air.

Feed Valve



Overflow Valve







Vacuum Piston


Compression Piston


Index Pin and Wheel

Patent Pending