What Degreasing Removes and Why It Matters
Copper tube is drawn with lubricants, and those lubricants remain on the surface as a film that is invisible but chemically active. In a refrigeration circuit the film carries compressor oil, moisture and particles into capillary tubes and expansion valves, and it can form a carbon deposit when joints are brazed. In a medical gas or oxygen pipeline the same film becomes a contamination source and, in oxygen service, a combustible residue. Degreasing is the controlled removal of that film, followed by drying and sealing so that the cleanliness achieved at the mill survives transport and storage.
The benefit is not only hygiene. A clean bore allows refrigerant to wet the tube wall evenly, keeps the heat transfer coefficient predictable, and reduces the risk of pinhole corrosion under a deposit. In food, pharmaceutical and high-purity gas service, cleanliness is a qualification requirement rather than a preference.
Standards and Cleanliness Requirements
Degreased tube is ordered against a product standard plus a cleanliness requirement. The most common combinations in export trade are listed below.
| Standard or specification | Scope |
|---|---|
| ASTM B280 / B280M | Seamless copper tube for air conditioning and refrigeration field service, ordered clean and dry with capped ends and a specified limit on residual internal contamination |
| ASTM B75 / B75M | Seamless copper tube for general service, used where ACR cleanliness is not required |
| EN 12735-1 and EN 12735-2 | Copper and copper alloy tubes for air conditioning and refrigeration; part 2 covers tubes for installation |
| Medical gas piping requirements | Hospital pipeline standards and national codes regulating oxygen, medical air and vacuum lines, which require oxide-free, degreased and capped tube |
ASTM B280/B280M is the reference most often quoted in purchase orders: it requires the tube to be supplied in a clean, dry condition with the ends capped, and it applies a quantitative limit to residual contamination on the internal surface. A degreasing certificate and the cleaning batch number should accompany the mill certificate, because cleanliness is a process result that cannot be verified from the analysis alone.
Production Process
Tube intended for clean service is drawn and then routed through a dedicated cleaning line, kept separate from ordinary mill stock so that oil cannot be re-introduced.
| Step | Purpose |
|---|---|
| Drawing and cutting to length | Section formed and ends cut square |
| Alkaline or solvent degreasing | Removes drawing lubricant, fingerprints and mill grease |
| Rinsing | Carries away loosened soil and cleaning agent |
| Drying | Removes moisture so that no water remains in the bore |
| Bore dry-nitrogen purge | Displaces air and prevents oxide growth on the clean surface |
| Capping and bundling | Seals the tube ends and protects the cleaned surface |
| Cleanliness verification | Residue test on a sample of the batch, with results recorded |
Tube is supplied in coils or straight lengths. Coils are wrapped and identified by batch, while straight lengths are capped at both ends and packed in a way that prevents abrasion between tubes.
Performance Advantages in Service
Hygiene: a grease-free bore does not support bacterial or mould growth carried by a nutrient film, which matters in drinking water, food and pharmaceutical lines.
Heat transfer: a clean internal surface keeps the refrigerant-to-wall coefficient stable and avoids the insulating effect of an oil film.
Brazing quality: less organic residue means less carbon, less porosity and more consistent joints.
System cleanliness: fewer particles and less oil carry-over reach valves, orifices and compressor sumps.
Corrosion control: deposits that would create oxygen concentration cells are removed, which reduces pitting in wet circuits.
Compliance: the tube can be released against medical gas, oxygen and high-purity gas specifications.
Copper itself brings the rest of the advantages: high thermal conductivity, ductility that allows tight coils without a seam, and natural resistance to a wide range of water chemistries.
Applications
Air conditioning and refrigeration circuits, including split systems, chillers, cold rooms and transport refrigeration.
Medical gas pipelines for oxygen, medical air, nitrous oxide and vacuum, and laboratory gas systems.
Oxygen and high-purity gas service, where a carbonaceous residue would be unacceptable.
Food and beverage, dairy and brewing lines where the tube forms part of the process boundary.
Pharmaceutical, bioprocess and semiconductor utility piping.
Cryogenic transfer lines that must remain free of moisture and oil before cool-down.
Handling, Installation and Cleanliness Control
Cleanliness is lost easily. The rules below are the ones that decide whether tube which left the mill clean reaches the system clean.
Keep the caps in place until the moment of assembly, and refit them whenever work stops.
Purge the bore with dry nitrogen while brazing so that no internal oxide scale forms; oxide inside a refrigerant or medical gas line is a contaminant.
Cut and flare with tools reserved for clean service; oil-based cutting lubricants must not be used on the tube end.
Store under cover, in a dry and ventilated place, off the ground, away from oil, grease and solvent fumes.
Do not wash the tube with water after degreasing; moisture in the bore must be avoided.
Verify cleanliness before closure of the system by a residue or wipe test on a representative sample, and keep the record with the installation documentation.
Where tube has to be stored for a long period before installation, it is kept sealed and inspected for internal moisture before use.
FAQ
Q: How clean is degreased copper tube?
The tube is supplied with a residual contamination level within the limit of the ordered specification, such as the internal residue limit of ASTM B280/B280M for ACR tube. Cleanliness is controlled by the cleaning process and verified on samples from each batch, with the result recorded on the cleaning certificate.
Q: Is degreased tube the same as ACR tube?
ACR tube is copper tube intended for air conditioning and refrigeration service, and it is supplied clean and dry with capped ends. Degreased tube is the material that meets that cleanliness requirement; orders should quote the product standard as well as the cleaning requirement so that the tube is produced on a controlled clean line.
Q: Can ordinary copper tube be degreased on site?
Site cleaning is difficult to control and rarely reaches the residue level of a mill cleaning line. For refrigeration, medical gas and oxygen service a mill-degreased, nitrogen-protected and capped product should be specified from the outset.
Q: Does degreasing affect the corrosion resistance or strength of the tube?
No. Degreasing removes a surface lubricant film only; it does not change the alloy, the temper or the mechanical properties of the copper, and it does not remove the natural protective oxide that forms in normal air.
Q: Why are the tube ends capped?
Caps keep moisture, dust and oil out of the bore during transport and storage. A tube that is stored uncapped can pick up contamination that no field cleaning step will reliably remove.
Q: What should be specified when ordering clean tube?
Grade and temper, dimensions, delivery form, the product standard, the cleanliness requirement, the capping and packaging method, and the test report that must accompany the delivery. Quoting the standard and the cleanliness limit together avoids any ambiguity about the material supplied.
