ASTM SA179/A179 Seamless Cold-Drawn Low-Carbon Steel Heat-Exchanger and Condenser Tubes
Overview
ASTM SA179/A179 is the specification for seamless cold-drawn low-carbon steel tubes specifically designed for heat exchangers, condensers, and similar heat transfer equipment. These tubes are characterized by their smooth surface finish, precise dimensions, and excellent thermal conductivity, making them ideal for efficient heat transfer applications.
Important Note:
SA179 is the ASME Boiler and Pressure Vessel Code designation
A179 is the ASTM designation
Both refer to the same material specification
Key Characteristics
Unique Features of SA179 Tubes:
Cold-Drawn Process: Provides smooth surface finish and precise dimensions
Low Carbon Steel: Excellent thermal conductivity
Seamless Construction: No weld seams to impede heat transfer or create failure points
Specialized Application: Specifically for heat exchangers and condensers
Surface Quality: Superior to general-purpose pipe for fouling resistance
Material Specifications
Chemical Composition (Maximum %):
| Element | Requirement | Purpose |
|---|---|---|
| Carbon (C) | 0.06-0.18 | Low carbon for good weldability and thermal conductivity |
| Manganese (Mn) | 0.27-0.63 | Strength without compromising thermal properties |
| Phosphorus (P) | 0.035 max | Impurity control |
| Sulfur (S) | 0.035 max | Impurity control |
| Silicon (Si) | Not specified | Typically low for maximum thermal conductivity |
Key Points:
Low Carbon Range: Specifically controlled for optimal properties
No Silicon Requirement: Unlike A106 which requires minimum silicon
Typically Killed Steel: But not explicitly required by specification
Mechanical Properties
| Property | Requirement | Notes |
|---|---|---|
| Tensile Strength | ≥ 47,000 psi (325 MPa) | Minimum only, no maximum specified |
| Yield Strength | ≥ 26,000 psi (180 MPa) | At 0.5% extension under load |
| Elongation | ≥ 35% in 2 inches | For wall thickness ≥ 0.015" |
| Hardness | Typically 72-85 HRB | Not specified but typical range |
Note: Mechanical properties are for as-finished cold-drawn condition. Annealing may be performed to meet requirements.
Manufacturing Process
Specialized Production:
Hot Rolling: Initial seamless tube production (typically to A106 or similar)
Cold Drawing: Multiple passes through dies to achieve:
Precise dimensions
Smooth surface finish
Improved mechanical properties
Heat Treatment (Optional):
Stress Relieving: For dimensional stability
Annealing: To meet mechanical properties if needed
Finishing:
Straightening
Cutting to length
Cleaning and inspection
Cold Drawing Benefits:
Surface Finish: Ra 32-63 μin (0.8-1.6 μm) typical
Dimensional Accuracy: Tight tolerances
Improved Strength: Through work hardening
Better Ovality: More round than hot-finished tubes
Size Range & Dimensions
Standard Sizes:
| Parameter | Range | Most Common |
|---|---|---|
| Outside Diameter | 3/16" to 3" (4.76 to 76.2 mm) | 5/8" to 1-1/4" |
| Wall Thickness | 0.015" to 0.165" (0.38 to 4.19 mm) | 0.035" to 0.109" |
| Length | Up to 65 feet (20 m) | 20-40 feet typical |
Common Tube Sizes for Heat Exchangers:
3/4" OD × 0.035" wall (BWG 18)
3/4" OD × 0.049" wall (BWG 16)
1" OD × 0.049" wall (BWG 16)
1" OD × 0.065" wall (BWG 14)
BWG (Birmingham Wire Gauge) is commonly used to specify wall thickness for heat exchanger tubes.
Dimensional Tolerances (Tighter than Standard Pipe)
Outside Diameter Tolerances:
| OD (inches) | Tolerance |
|---|---|
| ≤ 0.500 | ±0.004" |
| 0.501 - 0.625 | ±0.005" |
| 0.626 - 0.750 | ±0.006" |
| 0.751 - 1.000 | ±0.007" |
| 1.001 - 1.250 | ±0.008" |
| 1.251 - 1.500 | ±0.009" |
| > 1.500 | ±0.010" |
Wall Thickness Tolerances:
| Wall Thickness | Tolerance |
|---|---|
| ≤ 0.035" | ±10% |
| 0.036" - 0.065" | ±9% |
| > 0.065" | ±8% |
Note: Much tighter than standard pipe tolerances (typically ±12.5%)
Other Tolerances:
Length: +1/8", -0" for cut lengths
Straightness: 0.010" per foot maximum
Out-of-Roundness: Within OD tolerance
Testing Requirements
Mandatory Tests:
| Test | Requirement | Purpose |
|---|---|---|
| Hydrostatic Test | 1,000 psi or higher as calculated | Leak tightness |
| Flare Test | Expand end to specified diameter without cracking | Ductility for tube expanding |
| Flattening Test | Flatten to specified distance without cracking | General ductility |
| Tensile Test | One per lot | Verify mechanical properties |
| Hardness Test | Optional, often performed | Additional quality check |
| Nondestructive Test | Eddy current or ultrasonic optional | Defect detection |
Hydrostatic Test Pressure:
P=2StDP=D2St
Where S = 60% of specified minimum yield strength (15,600 psi)
Minimum test pressure = 1,000 psi
Flare Test Requirements:
| OD (inches) | Minimum Expansion |
|---|---|
| ≤ 1.000 | 20% increase in OD |
| > 1.000 | 15% increase in OD |
Critical for: Tube-to-tubesheet joints in heat exchangers
Surface Finish Requirements
Surface Quality:
Smooth Surface: Free from scale, pits, seams, and other injurious defects
Typical Roughness: Ra 32-63 μin (0.8-1.6 μm)
Visual Inspection: 100% visual examination
Special Finishes: Available for enhanced heat transfer or fouling resistance
Common Surface Conditions:
As-Drawn: Standard finish, light drawing lubricant may be present
Clean & Bright: Pickled or chemically cleaned
Phosphated: For corrosion protection and painting
Special Coatings: For specific service conditions
Applications
Primary Applications:
Shell and Tube Heat Exchangers:
Process heat exchangers
Coolers and heaters
Condensers and evaporators
Power Plant Equipment:
Surface condensers
Feedwater heaters
Air-cooled heat exchangers
Chemical & Petrochemical:
Reactor cooling jackets
Process interchangers
Waste heat recovery units
HVAC & Refrigeration:
Chiller tubes
Cooling coils
Heat recovery units
Typical Service Conditions:
Temperature: Up to 450°F (232°C)
Pressure: Moderate (typically < 300 psi)
Media: Water, steam, oils, process fluids
Environment: Typically clean service with proper water treatment
Why SA179 is Used:
Excellent Thermal Conductivity: Low carbon steel provides optimal heat transfer
Cost-Effective: More economical than alloy or stainless steels
Good Fabricability: Easy to expand, bend, and weld
Adequate Corrosion Resistance: For many water and process services
Proven Reliability: Long history of successful service
Comparison with Similar Standards
SA179 vs. A106:
| Parameter | SA179 | A106 Grade B |
|---|---|---|
| Primary Use | Heat exchangers, condensers | High-temperature piping |
| Carbon Content | 0.06-0.18% | ≤0.30% |
| Manufacturing | Cold-drawn | Hot-finished or normalized |
| Surface Finish | Smooth, precise | Standard mill finish |
| Tolerances | Tighter | Standard pipe tolerances |
| Temperature | Up to 450°F | Up to 750°F |
| Cost | Higher | Lower |
SA179 vs. A214 (ERW Heat Exchanger Tubes):
| Parameter | SA179 (Seamless) | A214 (ERW) |
|---|---|---|
| Manufacturing | Seamless cold-drawn | Electric resistance welded |
| Weld | No longitudinal weld | Has longitudinal weld |
| Surface Finish | Better | Good |
| Cost | Higher | Lower |
| Application | Critical service | General service |
SA179 vs. A334 (Low-Temperature Tubes):
SA179: For heat transfer at moderate temperatures
A334: For low-temperature service (cryogenic applications)
Different chemistry and testing requirements
Fabrication & Installation
Tube Expanding:
Critical Process for Heat Exchanger Assembly:
Expansion Method: Mechanical or hydraulic tube expanding
Expansion Ratio: Typically 3-8% of tube wall thickness
Sequence: Expand from center outward in tubesheet
Verification: Pull-out tests often performed
Considerations: Proper lubrication, tool maintenance
Welding SA179 Tubes:
Good Weldability: Low carbon content (CE typically < 0.35)
Filler Metal: ER70S-2 or similar low-carbon filler
Preheat: Generally not required for thin walls
Post-Weld Heat Treatment: Optional for stress relief
Common Methods: GTAW (TIG) for quality welds
Bending & Forming:
Cold Bending: Suitable for moderate radii
Minimum Bend Radius: Typically 3× OD
Mandrel Use: Recommended to prevent flattening
Springback: Account for in tooling design
Material Certification & Traceability
Required Documentation:
Mill Test Certificate: With chemical analysis and mechanical tests
Heat Number Traceability: Essential for ASME Code applications
Test Reports: Hydrostatic, flare, flattening tests
Dimensional Report: Often provided for precision tubes
ASME Certification: "SA" prefix indicates ASME Boiler Code compliance
Marking Requirements:
Manufacturer's name or trademark
Specification (SA179 or A179)
Size (OD × wall)
Heat number
Length (if cut to specific length)
Test pressure (if hydrostatically tested)
Typical Marking:
text
ABC CO SA179 0.750 x 0.049 H12345 20'-0"
Interpretation: Manufacturer=ABC CO, Spec=SA179, Size=0.750" OD × 0.049" wall, Heat=H12345, Length=20 feet
Quality Assurance
Critical Quality Parameters:
Surface Quality: Smooth, defect-free surface
Dimensional Accuracy: Within tight tolerances
Flare Test Performance: Must expand without cracking
Mechanical Properties: Meet minimum requirements
Straightness: Critical for tube bundle assembly
Common Defects to Avoid:
Surface Defects: Scratches, pits, seams
Dimensional Issues: Out-of-spec OD or wall thickness
Poor Straightness: Difficult tube insertion
Inadequate Flare Test: Indicates ductility problems
Contamination: Residual drawing lubricant or scale
Inspection Methods:
Visual Inspection: 100% examination
Dimensional Checks: OD, wall, length, straightness
Flare Test: Sample basis
Hydrostatic Test: Every tube
Eddy Current Testing: Optional for defect detection
Ordering Information
Essential Specification Data:
Standard: ASTM A179 or ASME SA179
Dimensions: OD × wall thickness × length
Quantity: Feet or pieces
End Condition: Plain, squared ends
Surface Finish: As-drawn, cleaned, etc.
Testing Requirements: Standard or additional
Certification: MTC requirements
Packaging: Protection requirements
Sample Order Specification:
text
ASTM A179 Seamless Cold-Drawn Steel Tubes Size: 0.750" OD × 0.049" wall (BWG 16) × 20' length Quantity: 5,000 feet Ends: Cut square, deburred Surface: Clean and bright Testing: Standard hydrostatic and flare tests Certification: Mill Test Certificate with chemical analysis Additional: Eddy current testing full length Marking: Per ASTM A179 with heat number Packaging: Bundle with end protection, moisture barrier
Special Requirements to Consider:
Eddy Current Testing: For critical service
Special Cleaning: For oxygen service or clean systems
Length Tolerances: Tighter than standard if needed
Straightness Requirements: More stringent for certain applications
Certification Level: ASME "SA" material for code work
Industry Standards & Code Compliance
ASME Boiler & Pressure Vessel Code:
Section I: Power Boilers (heat exchangers in boiler systems)
Section VIII: Pressure Vessels (most heat exchangers)
Section II, Part A: Material Specifications (SA179)
Required for: Code-stamped pressure vessels and heat exchangers
TEMA Standards:
TEMA Class R: Refinery service
TEMA Class C: Commercial service
TEMA Class B: Chemical service
SA179 is commonly specified for all TEMA classes
HEI Standards:
Heat Exchange Institute: Standards for surface condensers
SA179 is standard material for condenser tubes in many specifications
Economic Considerations
Cost Factors:
| Factor | Cost Impact | Notes |
|---|---|---|
| Cold Drawing | Higher than hot-finished | Precision manufacturing |
| Surface Quality | Additional processing cost | Cleaning, inspection |
| Testing | Additional tests add cost | Eddy current, etc. |
| Size | Smaller OD typically higher $/ft | Manufacturing difficulty |
| Quantity | Volume discounts | Typically >1,000 feet |
| Special Requirements | Increased cost | Tighter tolerances, etc. |
Price Comparison:
SA179 vs. A106: 50-100% higher (precision vs. standard)
SA179 vs. A214: 30-50% higher (seamless vs. welded)
SA179 vs. Stainless: 30-50% of cost (carbon vs. stainless)
Total Cost of Ownership:
Initial Cost: Higher than general-purpose pipe
Installation Cost: Similar to other precision tubes
Performance Cost: Lower due to better heat transfer
Maintenance Cost: Potentially lower with proper service
Lifecycle Cost: Often favorable due to reliability
Technical Summary
ASTM SA179/A179 seamless cold-drawn low-carbon steel tubes represent the standard material for heat exchanger and condenser applications where efficient heat transfer, reliability, and cost-effectiveness are paramount.
Key Technical Advantages:
Excellent Heat Transfer: Low carbon steel provides optimal thermal conductivity
Precision Dimensions: Cold-drawn process ensures tight tolerances
Smooth Surface: Minimizes fouling and improves heat transfer
Good Fabricability: Easy to expand, bend, and weld
Proven Reliability: Decades of successful service history
Selection Guidelines:
Choose SA179 when:
Building or repairing shell and tube heat exchangers
Installing surface condensers in power plants
Need efficient heat transfer with carbon steel
Require smooth, precision tubes for expanding into tubesheets
ASME Code compliance is required (use SA179)
Cost-effective solution vs. stainless or alloy tubes
Consider alternatives when:
Corrosive service requires stainless (A213 TP304/316)
High-temperature service (>450°F) requires alloy steel
Cost is primary driver and welded tubes are acceptable (A214)
Very high pressures require thicker walls (A106)
Special coatings or treatments are needed
Best Practices:
Material Selection:
Verify chemical composition meets requirements
Ensure proper heat treatment if specified
Check surface quality for heat transfer efficiency
Quality Assurance:
Require Mill Test Certificates
Verify flare test results for tube expandability
Check dimensional accuracy before installation
Consider eddy current testing for critical service
Fabrication & Installation:
Use proper tube expanding techniques
Follow qualified welding procedures
Ensure clean installation to prevent contamination
Perform leak testing after assembly
Operation & Maintenance:
Implement proper water treatment
Monitor for fouling and corrosion
Clean tubes regularly as needed
Inspect during shutdowns
Industry Perspective:
SA179 remains the workhorse material for heat exchanger tubes in countless industrial applications. Its combination of good thermal properties, fabricability, and reasonable cost makes it the default choice for many heat transfer applications. While newer materials and technologies have emerged, SA179 continues to be specified for the majority of carbon steel heat exchanger applications due to its proven performance and reliability.
Future Trends:
Enhanced Surface Treatments: For improved heat transfer and fouling resistance
Advanced Manufacturing: More precise cold drawing capabilities
Digital Documentation: Electronic material traceability
Global Standards Alignment: Harmonization with ISO standards
Sustainability Focus: Recycled content and energy-efficient production
Final Recommendation:
For carbon steel heat exchanger and condenser applications, ASTM SA179/A179 provides the optimal balance of performance, reliability, and cost. Its seamless cold-drawn construction ensures quality and consistency, while its low carbon chemistry provides excellent thermal conductivity. When properly specified, fabricated, and maintained, SA179 tubes deliver years of reliable service in demanding heat transfer applications.
Always consult applicable codes (ASME, TEMA, etc.) and involve qualified engineers when designing heat exchangers. Proper material selection, fabrication, and maintenance are essential for safe, efficient, and reliable long-term operation.
