June 9, 2020 Jeff Rosenblum
Did you know that ice can form in a vacuum even when it’s warm out? So what causes this (water freezing under vacuum) and how do we prevent it?
The state of water can be changed by changing the pressure to it. If we raise the pressure we can raise the boiling point. By lowering the pressure we can lower the boiling point. However, by lowering the boiling point by pulling a vacuum, we can also cause moisture to crystalize (freeze).
Now, if the vacuum pump was left on for long enough, the ice would eventually melt and change back to water and then be removed by the vacuum pump. A good way to test to see if you have moisture or ice is to valve off the vacuum pump during the evacuation process and observe the micron reading. If it continues to climb, you have one of two issues. It can be either moisture or a leak. A leak should have been found before this point when the system was pressurized prior to evacuation. This leaves us with moisture. If you suspect moisture in the system a triple evacuation can be used to speed up the evacuation.
The triple evacuation is a relatively simple task as outlined below:
Here are a few points to follow
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