Heat exchanger tubes are specialized steel tubes used in thermal exchange equipment such as shell-and-tube heat exchangers, condensers, evaporators, boilers, and other heat transfer apparatus. Unlike standard pipe used for fluid transport, heat exchanger tubes must meet stringent requirements for dimensional accuracy, surface quality, and heat transfer properties. The tube wall must be thin enough to allow efficient heat transfer between the internal and external fluids, yet strong enough to withstand the differential pressure between the tube side and shell side. The internal and external surfaces must be clean and smooth to minimize fouling and maintain heat transfer efficiency over time.
Heat exchanger tubes are used in a wide range of industries: petrochemical refineries (process heat exchangers, condensers, reboilers), power plants (condenser tubes, feedwater heaters, boiler tubes), HVAC systems (chillers, cooling coils), food processing (pasteurizers, sterilizers), and desalination plants (brine heaters, condensers). The selection of tube material, size, and wall thickness depends on the operating temperature, pressure, fluid corrosivity, and heat transfer requirements of the specific application.
ASTM A179 - Seamless Cold-Drawn Heat Exchanger Tube
ASTM A179 covers seamless cold-drawn low-carbon steel tube for heat exchangers, condensers, and similar heat transfer apparatus. The standard covers tubes with a maximum wall thickness of 4.2 mm (0.165 inch) and a minimum wall thickness of 0.5 mm (0.020 inch). The chemical composition requires carbon 0.06-0.18%, manganese 0.27-0.63%, and residual elements controlled to low levels. The low carbon content provides good weldability and formability, while the cold-drawn process produces the precise dimensional tolerances and smooth surface finish required for heat exchanger service.
The cold-drawn manufacturing process offers several advantages for heat exchanger tubes. Drawing through a die at room temperature produces excellent dimensional accuracy: OD tolerance of ±0.05 mm and wall thickness tolerance of ±5% are standard. The cold work also improves surface finish, with typical surface roughness Ra <= 0.8 μm. After cold drawing, the tubes are annealed to relieve internal stresses and restore ductility. The tubes may be supplied in straight lengths (typically 6-12 meters) or as U-bent tubes for U-tube heat exchanger configurations. Applications for A179 include shell-and-tube heat exchangers in refineries, condensers in power plants, oil coolers, and intercoolers in compressor systems.
ASTM A213 - Alloy & Stainless Steel Heat Exchanger Tube
ASTM A213 covers seamless ferritic and austenitic alloy steel boiler, superheater, and heat exchanger tubes. This is the most comprehensive standard for high-temperature heat exchanger tubes, covering grades from low-alloy T11 (1.25Cr-0.5Mo) through high-alloy T91 (9Cr-1Mo-V) and austenitic stainless grades TP304, TP316, TP321, and TP347. The "T" prefix in the grade designation indicates tube form (as opposed to "P" for pipe in A335). For austenitic stainless steel, common grades include TP304 (general corrosion resistance), TP304L (low carbon for welded applications), TP316 (improved corrosion resistance with molybdenum), TP316L (low carbon version), TP321 (stabilized with titanium for high-temperature service), and TP347 (stabilized with niobium).
A213 T11, T22, and T91 are ferritic alloy steel tubes used in high-temperature heat exchanger applications such as superheaters, reheaters, and feedwater heaters in power plants. These grades maintain their strength at elevated temperatures through the chromium-molybdenum alloy content. T91 is the highest-strength option, offering approximately three times the creep rupture strength of T22 at 600℃, allowing thinner tube walls and improved heat transfer. The maximum service temperature ranges from 593℃ (T11, T22) to 649℃ (T91, TP304, TP316). For detailed alloy steel property comparisons, see our .
ASTM A249 - Welded Stainless Steel Heat Exchanger Tube
ASTM A249 covers welded austenitic stainless steel tube for heat exchangers, condensers, and boilers. The tubes are manufactured from flat-rolled stainless steel strip or plate that is formed into a tube shape and welded using an automatic welding process (typically TIG or plasma arc welding with filler metal addition, or high-frequency induction welding). After welding, the tubes are cold drawn or cold worked to refine the weld zone microstructure and improve dimensional accuracy, then solution annealed to restore corrosion resistance and mechanical properties.
A249 welded tubes offer a cost-effective alternative to A213 seamless tubes, typically 10-20% lower in cost for the same material and dimensions. The welded tube has mechanical properties comparable to seamless after proper processing, with the weld joint efficiency factor typically 0.85-0.95 depending on the NDT performed. The standard requires the weld seam to be 100% inspected by eddy current testing (ECT) or hydrostatic testing. A249 is available in the same austenitic grades as A213 (TP304, TP304L, TP316, TP316L, TP321, TP347) with the same chemical composition requirements.
| ASTM A179 | ASTM A213 | ASTM A249 | |
|---|---|---|---|
| Seamless cold-drawn | Welded + cold working | ||
| 6-76 mm | 6-127 mm | 6-203 mm | |
| 400℃ | 649℃ (SS) | 649℃ (SS) | |
| Excellent (±0.05 mm) | Very Good (±0.10 mm) | Very Good (±0.10 mm) | |
| Low-pressure condensers | High-temp superheaters |
The standard OD range for heat exchanger tubes is 6 mm (1/4") to 50.8 mm (2"), though larger diameters are available for specialized applications. Wall thickness is commonly specified by BWG (Birmingham Wire Gauge) number, where a higher BWG number indicates a thinner wall. Common sizes include 10 BWG (3.40 mm), 12 BWG (2.77 mm), 14 BWG (2.11 mm), 16 BWG (1.65 mm), and 18 BWG (1.24 mm). For example, a 3/4" OD x 16 BWG tube has an OD of 19.05 mm and a wall thickness of 1.65 mm. The length is typically 6 m or 12 m for straight tubes, with U-bend tubes having specific bend radii depending on the heat exchanger design (typically 2-3 times the tube OD minimum bend radius).
Inspection of heat exchanger tubes includes dimensional verification (OD, ID, wall thickness, straightness, and length), eddy current testing (ECT) for detecting surface and subsurface defects, hydrostatic testing per the applicable standard, and mechanical tests including flaring (expanding the tube end to verify ductility) and flattening (crushing the tube to verify weld integrity for welded tubes). Surface cleanliness is verified by visual inspection and, for critical applications, by oil-and-grease swab tests.
Selecting the correct heat exchanger tube involves evaluating operating temperature (low-temperature < 200℃ use carbon steel A179; medium-temperature 200-500℃ use low-alloy A213 T11/T22; high-temperature > 500℃ use stainless steel or T91), medium corrosivity (non-corrosive use carbon steel; corrosive use 304/316 stainless; highly corrosive or chloride-laden use 316L or duplex), and heat transfer requirements (thinner walls provide better heat transfer but less corrosion allowance). Lifecycle cost analysis should consider initial material cost plus expected maintenance, cleaning frequency, and replacement interval in the specific service environment.
Contact our engineering team for expert tube selection and competitive pricing on A179, A213, and A249 tubes.
