ASTM A556/A556M specifies minimum-wall-thickness, seamless cold-drawn carbon steel tubes for use in tubular feedwater heaters.
The standard includes tubes bent into the form of U-tubes when specified.
Specified Standard Edition: ASTM A556/A556M-26
Standard Title: Standard Specification for Seamless Cold-Drawn Carbon Steel Feedwater Heater Tubes
ASTM A556 is application-specific. Its primary scope is feedwater heater tubing used in power and steam-cycle equipment.
| Parameter | Standard Scope |
|---|---|
| Outside Diameter | 5/8–1¼ in. [15.9–31.8 mm], inclusive |
| Minimum Wall Thickness | ≥0.045 in. [1.1 mm] |
| Wall Basis | Minimum Wall Thickness |
Tube dimensions outside this standard scope should not be represented as ASTM A556-compliant solely because they can be manufactured by the same production equipment.
ASTM A556 includes multiple carbon steel grades with grade-specific chemical, mechanical and hardness requirements.
The exact grade must be stated in the purchase specification and confirmed against the applicable ASTM A556/A556M requirements.
For quotation and production, the grade should not be omitted from the RFQ.
Chemical-composition requirements are defined according to the specified ASTM A556 grade.
Controlled elements include:
Material certification should identify the exact ASTM A556 grade and corresponding heat analysis.
Where project specifications impose additional chemistry restrictions, these should be provided at the enquiry stage.
ASTM A556 includes grade-specific mechanical-property requirements.
Applicable mechanical testing includes:
The required tensile strength, yield strength, elongation and hardness limits depend on the specified grade.
Mechanical-property values should therefore be verified against the exact ordered ASTM A556 grade rather than applying one generic value to all A556 tubing.
ASTM A556 requires finished tubes to receive the applicable heat treatment following the final cold-drawing operation.
Heat treatment is particularly important for feedwater heater tubing because the finished material must meet the required mechanical properties, hardness and fabrication performance.
For U-tube orders, any additional heat-treatment requirements associated with bending should be specified and reviewed against the applicable ASTM A556 requirements and project specification.
ASTM A556 specifically includes tubing bent into U-tube form when specified.
For U-tube projects, dimensional control is required for both the tube dimensions and the finished tube geometry.
| Required Information | Details |
|---|---|
| Material Grade | Exact ASTM A556 grade |
| Tube Outside Diameter | Required outside diameter |
| Minimum Wall Thickness | Required minimum wall thickness |
| Straight Length | Straight tube length before bending, where specified |
| Leg Length | Required straight leg length |
| Bend Radius | Required bend radius |
| Developed Length | Where specified |
| Tube Pitch | Where applicable |
| Drawing | Tube or bundle drawing |
| Quantity | Quantity by bend radius |
| Heat Treatment | Including post-bending requirements, if specified |
| Inspection | Required testing and inspection |
U-tube manufacturability should be reviewed against the required tube dimensions, bend radius and project drawing before quotation.
ASTM A556 feedwater heater tubes are subject to mechanical and integrity testing.
Applicable requirements include:
Optional supplementary requirements can also be specified by the purchaser.
A key ASTM A556 requirement is the nondestructive examination of each tube after the finish heat treatment following the final cold-drawing pass.
The test equipment must be capable of detecting defects over the entire cross section of the tube.
Project-specific requirements for the following should be identified in the purchase specification where applicable:
ASTM A556 includes hydrostatic testing as part of the required tube integrity verification.
Any additional project-specific hydrostatic test requirement should be stated at the enquiry and order stage.
ASTM A556 and ASTM A179 are both seamless cold-drawn carbon steel tube specifications, but their application scopes differ.
| Standard | Primary Application |
|---|---|
| ASTM A556 | Tubular feedwater heaters, including U-tubes when specified |
| ASTM A179 | Tubular heat exchangers, condensers and similar heat-transfer equipment |
For power plant feedwater heater projects, ASTM A556 should be identified directly when required by the equipment or project specification.
| Parameter | Capability |
|---|---|
| Product Form | Seamless Cold-Drawn Feedwater Heater Tube |
| Configuration | Straight Tube / U-Tube, subject to technical review |
| General Manufacturing Capability | Cold Drawn / Cold Rolled |
| ASTM A556 Manufacturing Requirement | Seamless and Cold Drawn |
| ASTM A556 Outside Diameter Range | 15.9–31.8 mm |
| Minimum Wall Thickness | ≥1.1 mm |
| Straight-Tube Length | Up to 40 m |
| U-Tube Supply | Subject to drawing and technical review |
| Inspection | Hydrostatic / UT / ET as specified |
| Documentation | MTC / Inspection Documentation / TPI as required |
| Supplementary Requirements | Available when specified |
| Third-Party Inspection | Available upon request |
| Custom Requirements | Subject to technical review |
| MOQ | According to dimensions, configuration and production requirements |
ASTM A556 standard requirements and FYN manufacturing capability are stated separately.
Actual tube dimensions, U-bend configuration and production availability are confirmed according to the specified grade, outside diameter, minimum wall thickness, length, bend radius, quantity and inspection requirements.
ASTM A556 seamless cold-drawn tubes are primarily used in tubular feedwater heaters within steam-cycle power systems.
For feedwater heating stages operating downstream of the boiler feed pump where ASTM A556 tubing is specified by the heater design.
For applicable feedwater heating stages where carbon steel A556 tubing meets the equipment design and water-chemistry requirements.
For heater designs using U-shaped tube bundles, with bend geometry manufactured according to the approved drawing and applicable specification.
For tubular feedwater heater configurations requiring straight seamless cold-drawn carbon steel tubes.
For power plant maintenance and retubing projects where existing heater documentation specifies ASTM A556.
Final material selection should consider design pressure, design temperature, feedwater chemistry, corrosion conditions and the equipment design specification.
Available documentation can include:
Required documentation and supplementary requirements should be specified during the RFQ stage.
Typical export packing includes:
U-tubes require packing designed to protect bend geometry and prevent deformation during handling and transportation.
Production lead time depends on grade, dimensions, length, U-bend configuration, quantity and inspection requirements.
For quotation, please specify:
ASTM A556/A556M + Grade + OD × Minimum Wall Thickness × Length + Quantity
| Required Information | Details |
|---|---|
| Standard | ASTM A556/A556M |
| Material Grade | Exact ASTM A556 grade required |
| Outside Diameter | Required outside diameter |
| Minimum Wall Thickness | Required minimum wall thickness |
| Configuration | Straight tube or U-tube |
| Length | Required tube length |
| Quantity | Required order quantity |
| Bend Radius | For U-tubes |
| Leg Length / Developed Length | Where applicable |
| Drawing | Tube drawing for U-tube projects |
| Heat Treatment | If specified |
| Testing | Hydrostatic / NDE requirements |
| Supplementary Requirements | If specified |
| Documentation | Inspection documentation requirements |
| Third-Party Inspection | If required |
| Delivery | Delivery destination |
For feedwater heater projects, send your tube list, bundle drawing or equipment specification for technical review.
For an accurate quotation, please send your required grade, outside diameter, minimum wall thickness, length and quantity.
For U-tube feedwater heater projects, please also provide:
Bend Radius + Leg Length + Quantity by Radius + Bundle / Tube Drawing
For replacement projects, an existing MTC, tube bundle drawing or feedwater heater specification can help verify the original material and dimensional requirements.
