ASTM SA179 / A179 Seamless Cold-Drawn Low-Carbon Steel Tubes

ASTM A179 (SA179) is the ASME Boiler Code version of the specification for seamless cold-drawn low-carbon steel tubes specifically designed for heat exchangers and condensers. The "SA" prefix indicates it is an ASME material approved for use in ASME Code construction (Section I, Section VIII).

Key Features

SA179 vs A179: The Difference

Critical Point: SA179 is identical chemically and mechanically to A179, but carries code approval for regulated construction.

Chemical Composition

Mechanical Properties

ASME Code Applications

Section VIII - Pressure Vessels:

Heat exchanger tubes in U-stamped vessels

Condenser tubes in coded systems

Reboiler tubes

Cooler tubes in process vessels

Section I - Power Boilers:

Economizer tubes

Low-temperature heat recovery tubes

Auxiliary heat exchanger tubes

Typical Code References:

UG-10: Acceptance of SA materials

Part UHT: Requirements for heat-treated materials

Table UHA-23: Allowable stresses for SA179

Manufacturing for Code Compliance

Additional Requirements for SA179:

ASME-approved mill (hold appropriate ASME cert)

Material test reports with ASME designation

Traceability maintained through fabrication

Welding procedures qualified per ASME Section IX

NDE per Code requirements

Cold Drawing Benefits (for Heat Transfer):

Smooth surface finish (better heat transfer)

Precise dimensions (reliable tube-to-tubesheet fit)

Improved mechanical properties

Testing & Inspection (Code Requirements)

Hydrostatic Test Pressure (Code Minimum):

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P = 1.5 × MAWP × (S_T / S_D) But not less than specification minimum (typically 1000 psi)

Applications in Coded Equipment

Power Industry:

Surface condensers (ASME Section III or Section VIII)

Feedwater heaters (U-stamped)

Closed cooling heat exchangers

Auxiliary coolers in nuclear/power plants

Petrochemical:

Shell & tube heat exchangers (U-stamped)

Process coolers in coded vessels

Reboilers in distillation columns

HVAC & Refrigeration:

Chiller bundles in pressure vessels

Heat recovery units meeting code

Ordering for Code Projects

Essential Specifications:

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ASME SA179 Tubes [Dimensions: OD × Wall × Length] [Condition: As-drawn or annealed] [For ASME Section [I/VIII] construction] [Certification: ASME Material Test Report required]

Example Purchase Order:

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ASME SA179 Tubes 19.05 mm OD × 2.11 mm Wall × 6,000 mm Length Annealed condition For U-stamped heat exchanger per Section VIII, Div. 1 Full ASME MTR with traceability

Code Allowable Stresses

From ASME Section II, Part D:

Note: Lower than A106 due to different application focus (heat transfer vs pressure piping).

Fabrication Requirements

Tube-to-Tubesheet Joints (Code):

Rolling/expanding: Per TEMA standards

Welding: Requires procedure qualification (ASME Section IX)

Strength welding: May require PWHT

Leak testing: Per Code requirements

U-Bend Requirements:

Minimum bend radius: Typically 1.5 × OD

Heat treatment after bending if required by design

Special inspection of bent sections

⚠️ Code Compliance Critical Points

For ASME Stamped Vessels:

Must use SA179 (not A179) for code construction

Supplier must be ASME-certified for material

Material test reports must show SA designation

Traceability must be maintained to final vessel

Common Code Violations:

Using commercial A179 in coded vessels

Accepting standard MTC instead of ASME MTR

Losing material traceability during fabrication

Not following code welding procedures

Quality Documentation

ASME Material Test Report Must Include:

SA179 designation

Heat number traceability

Chemical analysis

Mechanical test results

Heat treatment records (if applicable)

Manufacturer's ASME certificate number

Statement of compliance with ASME Section II

International Code Equivalents

Cost Considerations

Premium for SA vs A:

Material cost: 10-20% higher for SA179

Documentation: Additional cost for ASME MTR

Traceability: More stringent requirements increase cost

Value: Required for code compliance - not optional

When SA179 is Required:

ASME-stamped pressure vessels

Registered boilers

Jurisdictional requirements

Client specifications for code compliance

Insurance requirements

Maintenance & Re-tubing

For Coded Equipment:

Replacement tubes must also be SA179

Welding procedures must be re-qualified if changed

Post-repair inspection per original code

Data report updates required

Service Life in Code Service:

Typical: 15-25 years in well-maintained systems

Replacement criteria: Per original design specifications

Inspection intervals: Per jurisdiction requirements

In summary: ASME SA179 is the code-approved version of A179 seamless cold-drawn tubes for heat exchangers and condensers in ASME pressure vessel and boiler construction. While chemically and mechanically identical to ASTM A179, the SA designation carries legal significance for code compliance, requiring ASME-certified manufacturing, documentation, and traceability. For non-code applications, A179 is sufficient, but for stamped pressure equipment, SA179 is mandatory.