Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure
Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure
(OP)
Hello everyone,
I have an assignment to plot the volumetric ratio of air to water vs. the Hydrostatic Testing pressure for a pipeline hydrostatic test.
I have already researched Henry's law, but am struggling to find a volumetric variant of it and its equivalent constant to relate with pressure. Air trapped in the line also seems to vanish at a certain pressure (~600 psig?). How can dissolving oxygen be continuously a function of pressure if the air just sort of "snaps" into the water?
I would appreciate some direction.
Cheers!
I have an assignment to plot the volumetric ratio of air to water vs. the Hydrostatic Testing pressure for a pipeline hydrostatic test.
I have already researched Henry's law, but am struggling to find a volumetric variant of it and its equivalent constant to relate with pressure. Air trapped in the line also seems to vanish at a certain pressure (~600 psig?). How can dissolving oxygen be continuously a function of pressure if the air just sort of "snaps" into the water?
I would appreciate some direction.
Cheers!





RE: Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure
https://www.engineeringtoolbox.com/oxygen-solubili...
RE: Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure
The underlying issue is always "how much free gas is there in the hydrotest water that can collect in the high points?". The answer to that is indeterminate. I always fill the line with all the vents open and shut each vent when I get water out it. At the end of the fill, I leave the very highest vent open for 24 hours. Then I fill the line until I get water out the highest vent, and then go to each closed vent and open it until I get water. Then fill till the highest vent has water again, shut the highest vent and start the test. This technique has worked for tests in some pretty rough country in the Rockies. The only time it didn't work was when "the highest vent" was no where near the highest point in the line. We fought that test for a week before we got a good chart.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure
The air volume is found either by plotting pressure rise vs volume and then tracking back to zero pressure based on a straight line. Or plotting the pressurisation line and seeing how far out you are.
Air is 80% nitrogen....
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RE: Dissolved Air Volume/Fill Volume vs. Hydrostatic Testing Pressure