ASME SB163 N08825 Extruded Finned Tubes for Air Coolers
Product Overview
ASME SB163 N08825 Extruded Finned Tubes for Air Coolers are engineered heat-transfer components designed to improve air-side heat exchange in industrial air-cooled heat exchangers and finned tube bundles. Manufactured with UNS N08825 nickel-iron-chromium alloy base tubes, these products are intended for applications where corrosion resistance, mechanical integrity, and dependable heat-transfer performance are important to equipment reliability. Alloy 825 combines nickel, chromium, molybdenum, copper, and titanium to provide resistance to a range of reducing and oxidizing corrosive environments, including selected acidic process conditions. The extruded fin structure increases the external heat-transfer surface area available for air-side heat exchange, helping equipment designers meet thermal-duty requirements within a defined bundle footprint. Depending on the approved design, the fin sleeve may be mechanically expanded and extruded around the base tube to create a close-fitting fin-to-tube interface. The base tube specification, fin material, extrusion geometry, and operating limits must be selected together to ensure compatibility with the process fluid, ambient air, design temperature, and corrosion environment. These tubes can be configured to project-specific dimensions and supplied with agreed material traceability, dimensional inspection, and testing documentation. For air coolers operating in corrosive industrial environments, the combination of Alloy 825 base tubing and an appropriately selected extruded fin system can help address corrosion-related maintenance concerns, heat-transfer requirements, and equipment service-life objectives.
Product Features and Engineering Advantages
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Corrosion-resistant base tube: UNS N08825 is a nickel-based alloy designed to resist a range of corrosive media, including sulfuric and phosphoric acid environments under suitable conditions.
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Expanded heat-transfer area: Extruded fins increase the external surface area available for heat exchange with cooling air.
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Close-fitting fin structure: The extruded sleeve can provide a mechanically bonded interface when manufactured to the specified dimensions and expansion requirements.
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Configurable fin geometry: Fin height, thickness, pitch, tube length, and base tube dimensions can be selected according to the thermal design.
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Industrial air-cooler integration: Suitable for evaluation in process air coolers and finned tube bundles where base tube corrosion resistance is a key selection factor.
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Traceable manufacturing documentation: Material certificates and inspection records can be arranged according to the purchase order and approved inspection and test plan (ITP).
The fin material must be specified separately. Aluminum extruded fins are common in many air-cooler designs, but their suitability depends on the operating temperature, corrosive atmosphere, and required service life. The base tube grade alone does not establish the fin material or finished-product performance.
Application & Compliance
Usage Scenarios
| Application | Typical Service | Engineering Purpose |
|---|---|---|
| Industrial process air coolers | Cooling process fluids through air-cooled tube bundles | Transfer heat to ambient air |
| Petrochemical air-cooled heat exchangers | Process cooling in compatible corrosive environments | Support corrosion-aware heat exchanger design |
| Chemical processing cooling systems | Selected process streams requiring corrosion-resistant tubing | Reduce the risk of base tube degradation |
| Oil and gas process cooling | Project-specific fluid cooling duties | Provide a corrosion-resistant heat-transfer tube option |
| Custom finned tube bundles | Engineered air-cooled equipment | Increase air-side heat-transfer area within the available footprint |
Actual suitability depends on the process-fluid chemistry, design pressure, operating temperature, ambient conditions, fin material, and applicable equipment design code.
Chemical Composition
The following table summarizes typical specified chemical composition limits for UNS N08825 under commonly referenced Alloy 825 product specifications. The applicable ASME SB163 edition and the certified material test report (MTR/MTC) govern final acceptance.
| Element | Symbol | Requirement (wt. %) |
|---|---|---|
| Nickel | Ni | 38.0–46.0 |
| Chromium | Cr | 19.5–23.5 |
| Iron | Fe | ≥ 22.0 |
| Molybdenum | Mo | 2.5–3.5 |
| Copper | Cu | 1.5–3.0 |
| Titanium | Ti | 0.6–1.2 |
| Carbon | C | ≤ 0.05 |
| Manganese | Mn | ≤ 1.00 |
| Silicon | Si | ≤ 0.50 |
| Aluminum | Al | ≤ 0.20 |
| Sulfur | S | ≤ 0.030 |
All values are mass percentages. The actual certified chemistry must meet the applicable material specification. The Fe requirement is a minimum, rather than a simple balance designation, so it should be represented accurately in the material documentation.
Mechanical Properties
For UNS N08825 tubing in the applicable annealed condition, commonly specified minimum mechanical properties include the following. Confirm the exact requirements against the ordered edition of ASME SB163 and the specified product condition.
| Mechanical Property | Typical Requirement |
|---|---|
| Tensile Strength | ≥ 586 MPa |
| Yield Strength, 0.2% Offset | ≥ 241 MPa |
| Elongation in 2 in. (50.8 mm) | ≥ 30% |
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