⚙️ Technical SOP
AC Refrigerant Cylinder Refilling Process
Standard operating procedures for workshop technicians to safely evacuate, inspect, weigh, and refill recovery and charging cylinders with R32, R410A, and R22.
⚠️ CRITICAL SAFETY NOTICE (READ FIRST)
R32 Refrigerant is mildly flammable. Ensure absolutely no open flames, spark sources, or active electrical relays are within 10 feet of the refilling area. Always ensure active exhaust ventilation is running.
R410A Refrigerant operates under extremely high pressure. Use only heavy-duty hoses rated for at least 800 PSI burst pressure. Never use standard R22 hoses for R410A / R32 transfer.
01
Pre-Fill Safety Inspection & Setup
Physical inspection of hardware and scale calibration.
Inspect Cylinder Integrity & Hydro-Test Stamp
Verify the reusable cylinder is within its 5-year testing validity date. Inspect for dents, severe rust, or collar damage. Never refill disposable cylinders.
High Importance
Check Valve Threads & Pressure Relief Vent
Inspect target cylinder valve outlet threads for cross-threading or copper fillings. Check that the spring-loaded relief valve is clear of dirt or paint.
High Importance
Verify Color Code & Gas Matches Target
Verify that the gas type matches the target cylinder's designation (Rose/Pink for R410A, Red/Blue band for R32, Green for R22). Mixing gases is strictly forbidden.
High Importance
Calibrate Weighing Scale & Position Extinguisher
Place the digital charging scale on flat ground, tare it to zero, and verify weight accuracy. Keep a class BC dry chemical powder fire extinguisher nearby.
Standard
02
Cylinder Evacuation & Deep Vacuuming
Removing moisture and air impurities to prepare the cylinder core.
Connect Manifold to Vacuum Pump
Connect the blue low-pressure manifold hose to the target cylinder valve. Connect the yellow center charging hose to the vacuum pump inlet.
Medium
Pull Deep Vacuum to 30 in Hg / 500 Microns
Open the low-pressure manifold valve and target cylinder valve. Run the vacuum pump until the micron gauge settles below 500 microns (or needle reaches -30 in Hg).
High Importance
Conduct Vacuum Hold Test (5 Mins)
Close the low-pressure manifold dial valve and turn off the vacuum pump. Wait 5 minutes. Check that the dial does not rise, confirming no leak points.
High Importance
03
Liquid Phase Connection & Line Purging
Safe setup for liquid phase charging and clearing lines.
Determine Cylinder Tare Weight (TW)
Verify the Tare Weight stamped on the target cylinder shroud (e.g. TW 6.3kg). Note it down. Place the cylinder on the scale and tare it.
High Importance
Invert Source Mother Cylinder
To transfer refrigerant as a liquid phase, place the source cylinder upside down in a dedicated secure cylinder rack to keep it steady.
Medium
Connect High-Pressure Charging Lines
Connect the red high-pressure charging line from the inverted source cylinder outlet valve to the inlet valve of the target cylinder.
High Importance
Purge Hose Lines to Expel Air
Open the source cylinder valve slightly. Loosen the hose fitting at the target cylinder connection point for 2 seconds to blow out air, then lock tight.
High Importance
04
Liquid Phase Charging Process
Refilling step-by-step and calculating safe 80% boundaries.
Calculate 80% Safe Liquid Fill Limit
Find the Water Capacity (WC) value stamped on the cylinder. Safe max refrigerant weight is 80% of WC (Max Gas = WC × 0.8). NEVER exceed this limit.
High Importance
Slowly Open Cylinder Valves
Slowly open the target cylinder liquid valve first, then open the source cylinder liquid valve. Liquid refrigerant will begin flowing.
High Importance
Monitor Weight Increase in Real Time
Keep eyes on the scale display. Do not leave the refilling setup unattended for any reason. Keep tracking the accumulated net weight.
High Importance
Use Ice Bath for Pressure Differential (If Needed)
If pressure equalizes and transfer stops, cool the target cylinder shroud with ice water. WARNING: Never apply open flame or heat gun to the source cylinder!
High Importance
05
Pressure Cut-Off & Leak Inspection
Safe line decoupling and leak testing on connections.
Stop Charging at Target Net Weight
As soon as the scale reaches the calculated 80% safe net weight, close the target cylinder valve firmly, then close the source valve.
High Importance
De-pressurize Hoses Safely
Gently loosen the line connectors. Use the manifold bypass dial to vent or recover residual liquid refrigerant trapped in the charging lines safely.
Medium
Electronic Halogen Leak Search
Use an electronic leak detector around the target cylinder valve spindle, output collar, and pressure relief valve. Check for any trace R32/R410A leaks.
High Importance
Verify Gross Cylinder Weight
Remove the cylinder from the scale. Wipe the surface dry. Re-weigh the cylinder. Confirm Gross Weight equals Tare Weight + Net filled gas weight.
Standard
06
Labeling, Logging & Safe Storage
Safety tagging, logbook recording, and correct warehouse storage.
Apply Weatherproof Safety Label Tag
Affix a tag on the cylinder body stating: Gas Type (e.g. R32), Date Filled, Net Weight (in kg), Gross Weight (in kg), and Technician Initials.
Standard
Secure Brass Protection Cap & Plastic Plug
Screw the brass protection cap onto the valve outlet port to block dirt entry. Tighten the shroud's metal valve protection collar.
Standard
Register in Master Refill Logbook
Record the cylinder serial number, tare weight, gas type, net gas filled, gross weight, and date of fill in the workshop master register.
Medium
Store in Cool, Ventilated Area
Store cylinders upright. Lock in a well-ventilated cage out of direct sunlight, away from radiators, open flames, or heavy power switches.
High Importance