What Is a Closed Loop BHO Extraction System?
A closed loop BHO extraction system is the industry standard for professional hydrocarbon cannabis and hemp extraction. Unlike open blasting methods, a closed loop system contains all solvents within a sealed circuit, recovering and recycling butane and propane throughout the process. This makes it safer, more efficient, and compliant with state regulations for commercial extraction labs.
In this complete guide, we break down every step of setting up and operating a closed loop extractor, from gas distillation and vacuum procedures to material loading and final product discharge. Whether you are building your first extraction lab or training new technicians, this walkthrough covers the critical details that separate professional operations from amateur ones.
Equipment Overview: Choosing Your Closed Loop System
The system featured here is the Reinier closed loop system from Open Source Steel, customized with components sourced from Glacier Tanks. What makes this particular setup appealing for experienced technicians is the range of customizable options it offers. You can control every parameter, adjust flow rates, and fine-tune the system to produce shatter, wax, crumble, budder, or any texture you are targeting.
Key components of a professional closed loop system include:
- Extraction columns (single or dual column configurations)
- Solvent recovery tank with sight glass
- Collection vessel with jacketed base
- Condensing coil for vapor-to-liquid recovery
- Molecular sieve for solvent drying
- Haskell pneumatic pump for gas transfer
- Auxiliary chillers and heaters for temperature control
- Vacuum pump for atmosphere removal
- Scales for monitoring solvent weight
- LEL (Lower Explosive Limit) meter for safety monitoring
Setting Up Auxiliary Heating and Chilling Equipment
Before any extraction begins, you need to initialize your auxiliary temperature control units. These are the backbone of your process parameters.
Chiller Configuration
Chiller #1 controls the extraction column temperature. Power it on, wait for initialization, then activate the circulation and cooling functions. Set the target to negative 40 degrees Celsius. In operation, it will typically reach around negative 13 degrees Celsius, which is sufficient for clean, light-colored extracts.
Chiller #2 runs the condensing coil at negative 10 degrees Celsius. This coil is responsible for recondensing butane and propane vapors back into liquid form during solvent recovery.
Hot Water Heater
The hot water heater and circulation pump supply heat to both the solvent recovery tank and the collection pot at 115 degrees Fahrenheit. This temperature enables the boiling off of gas from liquid to vapor phase during the collection stage. Simply flip the switch to power it on.
C1D1 Lab Safety: Non-Negotiable Requirements
Your auxiliary heaters, chillers, and air compressor are not rated for Class 1 Division 1 (C1D1) environments. They are not explosion-proof. These units must be placed outside the rated laboratory space, with wall penetrations sealed using fire-blocking foam to maintain the C1D1 classification of your extraction room.
The pneumatic air hose for the Haskell pump, the chiller feed lines, and the heater supply lines all pass through sealed wall penetrations. This is not optional. If your lab is not set up this way, you are operating outside of safety compliance. For a deeper look at lab safety requirements, check out our guide on cannabis extraction lab safety and C1D1 setup.
Step 1: Distilling Your Solvent Gas
Even though solvent manufacturers claim their gas is “twice distilled,” real-world experience shows residual contaminants remain. These undesirables will transfer directly into your final product if you skip this step. Always distill your gas before running an extraction.
Connecting the Solvent Tank
Use a 3/8-inch braided gas hose rated for 300 PSI. When connecting to the solvent holding tank, remember that solvent tank fittings use reverse threading: righty loosey, lefty tighty. For all other connections, standard threading applies.
The golden rule for all fittings: finger tight, then a quarter turn. Never over-tighten brass fittings because they strip over time. For brass nuts, use a 5/8-inch deep socket wrench. A shallow socket will catch on the bolt end and prevent proper tightening. You will know the fitting is properly seated when you hear the faintest squeak.
Step 2: Pulling Vacuum on the System
Oxygen serves as both a catalyst for explosive environments and causes oxidative effects (like a red tint) in your oil. Before injecting any gas, you must pull vacuum on the entire system to remove atmosphere, oxygen, and residual moisture.
Vacuum Procedure
- Connect the vacuum pump to the top accessory port of the solvent recovery tank
- Open the accessory valve and watch the vacuum gauge begin to drop
- Open valves sequentially from source outward: molecular sieve, extraction columns (top and bottom), and discharge rails
- Leave the solvent recovery tank valves closed so you do not vacuum out your recovered gas
- Wait for the gauge to reach approximately negative 28 millibar (altitude affects this; higher elevations like Colorado will pull a slightly deeper vacuum)
Closing Vacuum and Leak Testing
Always close valves from back to front. This allows you to isolate each section of the system. After closing all valves, monitor the gauges for several minutes. If the vacuum reading climbs back toward zero, you have a leak. The sectioned-off valves help you pinpoint exactly where the leak is occurring.
Before every run, even before pulling vacuum, do a safety check on all connections. Brass nuts, hose fittings, and clamps loosen over time from repeated pressure cycling. A quick walk-around with a wrench takes two minutes and could prevent a catastrophic failure.
Step 3: Gas Injection and Distillation Run
For this process, a propane and butane combination is used. The specific gas ratio affects color, consistency, and terpene preservation in the final product. Consult your SOP for the exact mixture ratios for your target product.
Monitoring Gas Weight
Zero out both scales before beginning. The tare weight should already account for the empty solvent tank weight so you can accurately track how many pounds of gas enter the system. For a standard distillation run, 40 pounds of gas is loaded into the solvent recovery tank.
Running the Gas Loop
Open valves sequentially from source forward, then from the end back to the source. This is the same protocol used during vacuum: follow the line forward, follow the line backward, every time, no exceptions. Watch the pressure gauge rise as gas enters the extraction column. Open slowly and never slam gas through the system.
Once gas is flowing through the full loop (extraction column to collection vessel to molecular sieve to Haskell pump to condensing coil and back to the solvent tank), activate the Haskell pump. Target a pump cadence of approximately 120 BPM. Keep constant watch on your gauges, sight glass flow, and both scale readings.
After achieving full recovery and watching both gauge pressures drop, shut off the Haskell pump, close the stop valve, and bleed any excess pressure while monitoring the LEL meter. Then disconnect heater hoses, unbolt the collection pot, and clean out the residual contaminants that the “clean” gas left behind.
Step 4: Loading Cannabis into Extraction Columns
With clean, distilled gas now in your solvent tank and a verified vacuum on the system, you are ready to load biomass.
Using Extraction Bags
Extraction bags (approximately 25 microns) keep all plant particulate contained while allowing extracted oil to pass through. Each bag holds roughly 2.5 to 5 pounds of material. Pack the biomass with a light touch. You want enough density to prevent channeling but not so tight that solvent flow is restricted.
Sealing the Columns
After loading, clean the sealing groove thoroughly with a paintbrush to remove any residual plant powder. Even a small amount of particulate in the groove will compromise your seal and create a leak. Replace the PTFE O-ring evenly, seat the cap, and tighten the tri-clamp with your 5/8-inch deep socket. Ensure even spacing on both sides of the clamp for uniform compression. Listen for the squeak that confirms proper tightness.
Step 5: Running the Extraction
After re-establishing vacuum on the loaded columns, zero your scale and begin injection. The target ratio is approximately 2 pounds of gas per pound of biomass. For 6 pounds of loaded material, run approximately 15 pounds of solvent through the system.
Soak Time: The Myth
Many operators believe longer soak times increase yield. This is not accurate. Extended contact time between solvent and biomass pulls more undesirable compounds, including chlorophyll and darker waxes, resulting in a darker, lower-quality product. Saturate the material quickly and effectively, then move the solution to the collection vessel as fast as your system allows.
Recovery and Discharge
Open all discharge valves sequentially to send the cannabinoid-rich solution to the solvent recovery tank. Activate the Haskell pump to accelerate gas recovery. Once 12 pounds of gas has been recovered, cut the gas at the source. To prepare for discharge, add a small spritz of nitrogen to the system, then open the discharge nozzle over a parchment paper boat to collect your slab.
The result is a clean, properly extracted slab ready for post-processing into shatter, wax, crumble, live resin vape carts, or other concentrate textures through vacuum oven procedures. If your target is THCa diamonds, that same crude feeds directly into a reactor-based crystallization workflow. Our THCa crystallization SOP covers reactor setup, solvent selection, and the full diamond-growing process from BHO crude.
Related Guide: After extraction, your crude will need winterization to remove fats and waxes before distillation. Our complete winterization guide covers the full process including BHO-specific ethanol ratios, filtration parameters, and solvent recovery.
Key Takeaways for Professional Closed Loop Operation
- Always distill your gas before extraction, regardless of manufacturer claims
- Finger tight plus a quarter turn on all fittings. Never over-tighten brass
- Pull vacuum before every run to remove oxygen and moisture
- Follow the line forward, follow it backward when opening and closing valves
- Monitor everything: gauges, scales, sight glass, LEL meter
- Minimize soak time for lighter, cleaner extracts
- Clean your sealing grooves before reassembly to prevent leaks
- C1D1 compliance is non-negotiable for any commercial operation
Ready to level up your extraction game? Contact WKU Consulting for personalized guidance on building your extraction lab.
For more deep dives into cannabis chemistry, extraction SOPs, and lab design, subscribe to the WKU Consulting YouTube channel. New videos every week covering everything from distillation theory to advanced cannabinoid conversions.
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