I started testing the vacuum pump to see if it could draw down lower than previous tests.
I was only able to draw about 25 inHg in previous tests. So today, I started tracking down issues with the vacuum system.
What I found was encouraging. See, to be used in a freeze dryer, the pump has to draw down to 600 Pa or lower. A rough calculation tells us the pump will need to draw down to less than 29.2 inHg.
Sealing hoses and fittings for vacuum use can be a challenge. A leak does not manifest itself as a drip, for instance. It cannot be observed from outside. Basically, everything is backwards.
I found the vacuum canister had a design flaw in its fitting port. I fixed that flaw. It took some doing, but the seal is now reliable and vacuum tight.
I fixed a few hose leaks and a leaky valve packing.
Sealing most vacuum leaks can be performed like any other leak. The difficult part is finding the leak.
I used Vacuum Grease to seal threads and hose fittings. It is designed to do just that.
I was eventually able to draw down to the limit of the gauge on the vacuum canister. But it is way better than it was in previous test. I will have to hook the vacuum sensor up to the canister to get a more accurate reading.
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