Deep Vacuum, Micron Gauges & Decay Testing

Build a high-flow evacuation setup

• Use clean, dry vacuum-rated hoses with as few restrictive fittings as practical.
• Core-removal tools can greatly reduce restriction when the service-valve design and procedure allow their use.
• Connect the micron gauge where it represents system pressure, preferably away from the vacuum pump rather than directly at the pump inlet.
• Use fresh vacuum-pump oil and change it when contamination or moisture reduces pump performance.

Evacuate the system, not just the hoses

Pull the system into a deep vacuum and allow time for moisture to boil out of oil, tubing, and components. Large systems, wet systems, and systems exposed to atmosphere for long periods may take substantially longer.

• If moisture is stubborn, follow approved dehydration practices; dry nitrogen may be used as part of a manufacturer/company-approved evacuation process.
• Watch how the micron level behaves, not just the lowest number reached.

Isolation and decay matter

• Isolate the pump from the system and observe the micron rise for the period required by your procedure or the manufacturer.
• A rapid, continuing rise may indicate a leak or significant remaining moisture/outgassing; the shape and stabilization of the rise provide useful clues.
• 500 microns is a widely used field benchmark, but it is not a universal pass/fail rule for every manufacturer or system. The specified target and acceptable decay are what govern the job.

Before charging

Confirm the system holds the required vacuum/decay test, close/isolate service equipment correctly, and introduce refrigerant in the manner required for that refrigerant and equipment. Record the final evacuation result as part of the service documentation.