What is API 605?
API 605 was the American Petroleum Institute standard for large-diameter carbon steel flanges, and is the direct predecessor of the ASME B16.47 Series B dimensional series that replaced it.
Key Takeaways
- API 605 scope: Weld neck and blind flanges in large diameters, in a more compact and lighter geometry than the MSS SP-44 series that became B16.47 Series A.
- Size range: NPS 26 inch to 60 inch.
- Ratings: Class 75, 150, 300, 400, 600 and 900.
- Material grades: Carbon steel to ASTM A105 and A350 LF2, with alloy and stainless grades to A182 on request.
- Kalp Alloys manufactures to API 605 in Ahmedabad, India, with EN 10204 3.1 and 3.2 certification issued in its own name.
- Third-party inspection by SGS, BV, TUV or Lloyds can be witnessed at our plant before dispatch.
What API 605 governs
API 605 was the American Petroleum Institute standard for large-diameter carbon steel flanges, and is the direct predecessor of the ASME B16.47 Series B dimensional series that replaced it.
Weld neck and blind flanges in large diameters, in a more compact and lighter geometry than the MSS SP-44 series that became B16.47 Series A.
Scope, sizes and ratings at a glance
The envelope below is the practical reference: what to state on a purchase order so the item that arrives is the item the line needs.
| Parameter | Detail |
|---|---|
| Size range | NPS 26 inch to 60 inch |
| Ratings | Class 75, 150, 300, 400, 600 and 900 |
| Material grades | Carbon steel to ASTM A105 and A350 LF2, with alloy and stainless grades to A182 on request |
| Status | Withdrawn — superseded by ASME B16.47 Series B |
| Size range | NPS 26 inch to 60 inch |
| Classes | 75, 150, 300, 400, 600, 900 |
| Relative geometry | Lighter and more compact than MSS SP-44 / B16.47 Series A |
| Modern equivalent | ASME B16.47 Series B |
| Interchangeable with Series A | No |
The point buyers most often get wrong
API 605 has been withdrawn and superseded by ASME B16.47 Series B, but the API number still appears on older isometrics and on plant built before the changeover. A buyer replacing a flange on such a line will order by the API number because that is what the drawing says. We manufacture to the B16.47 Series B geometry and confirm on the quotation that it supersedes and matches API 605, so there is no ambiguity about whether the replacement will fit.
What Kalp Alloys manufactures to API 605
Kalp Alloys is a manufacturer, not a stockist. Production runs at our own facility at 5, Jay Vijay Industrial Estate, B/h. Akash Vikas Estate, Keval Kanta Road, Rakhial, Ahmedabad, which means the heat number stamped on the part traces to our own melt record and the mill test certificate is issued in the name of Kalp Alloys.
That matters on standard-led purchasing more than anywhere else, because an approved-vendor submission or a code-governed line has to show who made the part. A certificate passed down a trading chain names a mill the buyer has no relationship with and cannot query.
Grades supplied against API 605 cover Carbon steel to ASTM A105 and A350 LF2, with alloy and stainless grades to A182 on request. Non-standard bores, thicknesses, drilling patterns and facing finishes are produced to customer drawing.
Ordering against API 605
State the dimensional standard, the size or NPS range, the rating or schedule, the facing where applicable, the material specification and grade, the quantity, and the certification level required. A quotation is typically returned within 24 hours.
Drawings for non-standard items can be sent by email or on WhatsApp at +91 81608 73937 and are reviewed by the technical team. Stock sizes dispatch in three to seven days; made-to-drawing items carry a firm lead time quoted at order confirmation. There is no minimum order on stock sizes and trial quantities are accepted.
Frequently Asked Questions
API 605 was the American Petroleum Institute standard for large-diameter carbon steel flanges, and is the direct predecessor of the ASME B16.47 Series B dimensional series that replaced it.
NPS 26 inch to 60 inch. Ratings covered are Class 75, 150, 300, 400, 600 and 900.
Carbon steel to ASTM A105 and A350 LF2, with alloy and stainless grades to A182 on request.
No. It has been withdrawn and replaced by ASME B16.47 Series B, which carries the same dimensional geometry. We manufacture to B16.47 Series B and confirm the API 605 equivalence on the quotation.
Because plant built before the changeover was designed to it, and the isometric was never reissued. Ordering by the number on the drawing is correct practice; the supplier is responsible for confirming the current equivalent.
Yes. Kalp Alloys manufactures to API 605 at its own facility at 5, Jay Vijay Industrial Estate, B/h. Akash Vikas Estate, Keval Kanta Road, Rakhial, Ahmedabad, and issues the EN 10204 3.1 or 3.2 mill test certificate in its own name rather than passing through a third-party mill certificate.
An EN 10204 3.1 mill test certificate as standard, stating the ordered standard, grade and heat number, with chemical and mechanical results and a dimensional inspection report. EN 10204 3.2 with third-party inspection by SGS, BV, TUV or Lloyds is arranged where the project requires it.