ASTM A358 is not a single, uniform inspection package. The class named on the purchase order changes the welding arrangement and radiography requirement, so “ASTM A358 pipe” alone may be too vague for a project quotation.
What the five classes mean
| Class | Weld arrangement | Radiography stated in the ASTM scope |
|---|---|---|
| 1 | Double welded, filler metal in all passes | Complete |
| 2 | Double welded, filler metal in all passes | Not required by the class |
| 3 | Single welded, filler metal in all passes | Complete |
| 4 | As Class 3, except the pass exposed to the inside may be made without filler metal | Complete |
| 5 | Double welded, filler metal in all passes | Spot |
This summary follows the published ASTM A358/A358M scope. Read the required edition and project specification for the full manufacturing, examination, repair, heat-treatment and test rules. “No radiography required by the class” does not prohibit a project from specifying additional examination.
What to put on the purchase order
- ASTM A358/A358M with edition and the exact class.
- Grade, NPS or outside diameter, wall or schedule, length and quantity.
- Service conditions and applicable design code, if specified by the engineer.
- Heat treatment, end preparation and any supplementary requirements.
- Examination scope, acceptance criteria and records required for this project.
Do not substitute the product standard casually
ASTM A358 electric-fusion-welded pipe and ASTM A312 pipe cover different material specifications. The industrial pipe category is the commercial overview; the specified design code and drawing control any substitution.
FAQ
Does Class 2 mean a pipe has no inspection?
No. It describes the class’s radiography requirement, not the entire testing and inspection program. Review the standard and project order.
Can the supplier choose the class?
The purchaser should state the class or obtain engineering confirmation before an alternative is quoted. Send the class and drawing for review.