We’re often asked what type of pump is best for making Butane Honey Oil (BHO) and other types of botanical extractions. When pairing a vacuum oven with a vacuum pump, there are three important things to consider:
2) Oven size
3) Optimal purge pressure
The Right Tool for the Job
Application is the first thing that must be considered. For the botanical industry, the best pumps for the job are oil-free, chemical-duty pumps like the Welch 2042B-01, the Welch 2052-B-01 diaphragm pumps, or the Agilent Varian IDP-3 or the Edwards nXDS-C series scroll pumps. All these pumps are designed to handle the types of solvents typically used in botanical extraction – typically butane, propane and CO2.
Unfortunately, the pumps most poorly suited to botanical extraction – those that use oil to create suction – are among the most commonly used (primarily since they are so inexpensive). There are several reasons to avoid these pumps. First and foremost is the fact that the very solvents you’re purging are great at breaking down oil (and in the case of CO2 extraction, where you’re removing a lot of excess moisture, the water condenses and displaces the oil). This creates a lot of wear and tear on the pumps and leads to premature failures, which are usually not covered under manufacturer warranties.
Second, these pumps emit oil vapor, which pollutes your work environment. If this vapor comes into contact with your valuable extract, it cannot be removed. Third, under certain conditions (such as a pump failure, power failure or operator error) that negative pressure in an oven can cause the oil to be sucked back into the vacuum oven and render your extract worthless. Ruining several thousand dollars of extract to save a few hundred dollars in pump costs is bad business.
If you must use an oil pump, locate the pump outside your lab environment. Also, let it warm up prior to purging and continue to run it when finished. Many people turn the pump on and off throughout the purge to try to save wear and tear on the pump. This actually is much harder on the pump; just let it run.
Another important consideration when choosing the pump is size, which should correspond to the size of your oven. As a general rule, the pump should have a CFM rating of .5x to 1.5x the volume of your oven.
Too Much Vacuum Can Really Suck
When it comes to botanical extraction, bigger is not necessarily better, and it’s possible to have too much of a good thing. For solvent or moisture purging, the key is to remove the solvents without removing the cannabinoids, terpenes or anything else.
Vacuum percentage is measured in inches of mercury or millimeters of mercury (torr). At 29.88 inches of mercury (1 Torr) most cannibinoids and terpenes stay in solution. Below 1 Torr, cannibinoids – including Delta-9-THC (a.k.a. “the good stuff”) – begin to boil and purge. That’s not what you want.
This is why we recommend pumps like the Welch 2052B, which can be left running with the vacuum valve open and will hold the perfect oven atmosphere without going over, which is the ideal way to purge as quickly and efficiently as possible. The Agilent Varian IDP-3, which is capable of pulling a deeper vacuum, can also be adjusted to create perfect purge conditions.
Visit our vacuum pumps page to see our whole lineup and see which is right for you.