In another blog post I discuss the process of filtering vacuum pump oil. But why filter vacuum pump oil? Cleaning and removing water from your oil allows you to reuse the expensive vacuum pump oil several times. Refilling the vacuum pump with clean oil that is free of water helps ensure the pump has a long life. Continually operating the vacuum pump with dirty oil that contains moisture will lead to early pump failure.
In the picture below you will see vacuum pump oil in a quart jar. This oil ran one complete freeze dry cycle before being drained into the jar, It sat for around 24 hours to allow the water to collect at the bottom. The cloudy mess in that jar is food particles from the food. It is drawn out of the freeze dryer as the vacuum pump pulls a vacuum on the chamber and makes it into the oil. You will be able to see what the oil should look like below after I discuss removing the water from the oil.
Remove the water from the oil
To remove the water from the used vacuum pump oil we start by draining the used oil into a quart mason jar. Secure a lid and ring on the jar and place it into the freezer and allow the water to freeze solid.
You can see the water under the oil in our mason jar in this picture. This was a significant amount of water and is not typical. This was a result of a long freeze dry cycle with a full load of very high moisture content food.
Once the water is frozen solid pour off the oil into your filter and allow the very viscous oil to drain into the toilet paper filter. (You can see my Brita TP filter in the picture at the bottom of this page.)
After the majority of the oil is out of the mason jar and before the water begins to melt, I transfer the jar to the filter that came with the Freeze Dryer unit. There the remainder of the oil drains from the jar along with the water as it melts. Once there is a fair amount of oil in the Harvest Right filter it too will go into the freezer to remove the water.
Here is what it looks like after filtering
This is the exact same oil as shown in the first picture after it went through our toilet paper filtering system. The difference is remarkable. One can see how much particulate matter was in that oil before filtering. Clean and filtered vacuum pump oil generally should look like this amber color. Some vacuum pump oil will be a different color, but this is what our Black Gold oil looks like.
So why filter vacuum pump oil? doing so will reduce operating cost and help reduce expensive repairs to the vacuum pump.
Filtering vacuum pump oil is a part of owning a home freeze dryer. It is necessary to remove moisture and food particles from the oil through filtering. Oil from the vacuum pump should be filtered after every load. This helps to ensure a long life of the vacuum pump.
When you purchase a Harvest Right freeze dryer you will receive a filter like the one in the picture below. The Harvest Right filter is the one on the left. It works and does filter out the particulate matter. Unfortunately I found it to be poorly assembled and messy to use. The Brita filter on the right is what we now use.
The Harvest Right oil filter
If you look at the picture above you will see the Harvest Right filter on the left. Initially we used the HR filter that came with the freeze dryer. To remove the filtered oil you have to unscrew the lower lid and lift everything out of the bottom container. It will drip oil and needs to be placed on something to soak up any oil. We grew tired of the mess and having to assemble and disassemble the filter. Now we use the Brita filter on the right in the picture. It is discussed below.
Our Brita oil filtering system
While this system is what we currently use, the idea wasn’t our own. We borrowed the idea from a freeze dryer group and have adopted it for our purposes.
For our filtering system we bought a 10 cup Brita pitcher. These filtering pitchers can be bought new for around $25. For the bargain minded folks, try looking for one in thrift stores. I’ve seen people reporting to find them for just a few dollars.
This Brita filter uses toilet paper rolled up to remove food particles. The toilet paper rolled up will replace the charcoal filter. As the filter gets full simply replace the toilet paper. In the picture below you can see an example of the filter material needing replaced.
How the Brita filter is better than the Harvest Right filter
The Brita filter does not require disassembly to pour the filtered oil back into the vacuum pump. So long as there isn’t oil in the upper chamber you simply grab the pitcher and pour the clean oil.
A quick important note, the toilet paper filter does absorb some oil and you will lose some of it. You will need to have extra vacuum oil on hand to replace what is lost each time you add new filter material. Black gold vacuum pump oil is what we use and is one of the two brands recommended by Harvest Right.