Boiler builders often accept welded tubes for water walls and flues where a seamless tube would only add cost, and ASTM A178 is the specification that makes that possible, with every tube heat treated after welding so the seam matches the body. The weld is not the weak point. ASTM A178 boiler tubes are electric resistance welded carbon and carbon-manganese steel tubes, made to minimum wall in Grades A, C and D. They are used for boiler tubes, flues, superheater flues and safe ends in power and process plants across Oman. Seamless boiler grades are on the carbon steel seamless pipes and tubes hub.
Where A178 Tubes Are Used
- Water-wall and generating bank tubes in water-tube boilers
- Boiler flues and fire tubes in fire-tube and package boilers
- Superheater flues within carbon steel limits
- Safe ends joining tubes to headers (Grade A only where forge welding is involved)
- Economisers and HRSG sections where the design code accepts welded tube
Where seamless tube is required, ASTM A192 and ASTM A210 Grade A1 are the usual seamless equivalents.
Choosing Between A178 Grades A, C and D
|
Grade |
Steel type |
Min. tensile / yield (MPa) |
Nearest seamless equivalent |
Notes |
|---|---|---|---|---|
|
A |
Low-carbon |
No tensile requirement in the standard |
A192 |
Soft, easy to expand; suitable for forge-welded safe ends |
|
C |
Medium-carbon |
415 / 255 |
A210 Grade A1 |
Higher strength; not suitable for forge-welded safe ends |
|
D |
Carbon-manganese |
485 / 275 |
A210 Grade C |
Highest strength; not suitable for forge-welded safe ends |
Grade A has chemistry limits but no tensile requirement, so where a design needs guaranteed strength, Grade C or D is specified. Grades C and D share their tensile values with A210 A1 and A210 C, which makes them a straightforward welded substitute where the code and purchaser allow it.
A178 Tubes and Sour Service
A178 tubes carry water and steam and are not a normal sour service material. If proposed for a process duty with H2S, NACE MR0175 / ISO 15156-2 applies, with a 22 HRC (250 HV) hardness limit that includes the weld seam. State any sour requirements in the RFQ; they are confirmed at quotation.
A178 Price Factors
- Grade (A, C or D)
- OD, minimum wall and length
- Inside bead trimming requirements
- Quantity and mill minimums
- Stock availability versus a mill order
- Supplementary tests such as the crush test
- Certification (EN 10204 3.1 or 3.2) and third-party inspection
- Incoterm and destination port
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation:
grade, OD, minimum wall, length, quantity, end preparation, bead requirements, supplementary tests, certification, inspection, destination port and required date.
A178 Certificates and Inspection
A178 tubes are supplied with EN 10204 3.1 mill test certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Certificates show grade, chemistry, heat treatment after welding, tensile results for Grades C and D, flattening, flange and reverse flattening tests, and the hydrostatic or electric test record. See the MTC and EN 10204 certification guide.
Packing and Storage
Lead time is confirmed at quotation. Tubes are bundled with end caps and rust-preventive coating, and kept under cover on Gulf sites so humidity and sand stay out of the bore. Keep grades clearly marked, since A, C and D look identical.
Related Boiler Tubes
A178 is used mainly in power generation and desalination and water treatment boilers.
ASTM A178 Boiler Tube FAQ
Are A178 tubes seamless or welded?
Welded. A178 covers electric resistance welded tubes, heat treated after welding. The seamless alternatives are A192 and A210.
What is the difference between A178 Grades A, C and D?
Grade A is low-carbon steel with no tensile requirement. Grade C is medium-carbon with 415 MPa tensile and 255 MPa yield. Grade D is carbon-manganese with 485 MPa tensile and 275 MPa yield.
Can A178 Grade C or D be used for safe ends?
Not where the safe end is forge welded. The standard notes that Grades C and D are not suitable for safe-ending by forge welding.
What sizes does A178 cover?
Usually 12.7 mm to 127 mm OD, with minimum walls from 0.9 mm to 9.1 mm.
Is SA-178 the same as A178?
Yes. SA-178 is the ASME Boiler and Pressure Vessel Code adoption of ASTM A178.
What should I send for an A178 quotation?
Send the grade, OD, minimum wall, length, quantity, end preparation, bead requirements, tests, certification, inspection, destination port and required date.
Request a Quote for ASTM A178 Boiler Tubes
Send the grade, OD, minimum wall, length and quantity, with the boiler tube schedule attached. Every enquiry is checked against ASTM A178 before the offer is prepared, so a Grade C or D tube listed for a forge-welded safe end is raised at the start.