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What should you check on a mill test certificate?
Short answer
Check that the heat number matches the material marking, that every specification claimed shows its required tests, that actual results fall within limits, that ordered supplementary tests and heat treatment are reported, that units and editions are right, and that the certificate type, 3.1 or 3.2, matches the purchase order.
Key takeaways
In brief
- The seven checks: The heat number on the MTC matches the material marking All claimed specifications (e.g.
The seven checks
- The heat number on the MTC matches the material marking
- All claimed specifications (e.g. A106/A53/API 5L) show their required tests
- Actual values, not just "OK", are within limits
- Supplementary tests ordered (IGC, impact, HIC) are reported
- Heat treatment is stated and correct
- Units and specification editions are right
- Certificate type (3.1 / 3.2) matches the order
More in our MTC guide.
A worked example of a dual-certified pipe
Take seamless pipe certified "ASTM A106 Gr B / ASME SA106 / API 5L Gr B PSL 1". The certificate has to show the chemistry and tensile results that satisfy all three, the hydrostatic or NDE test required by each, and the dimensions. If API 5L PSL 2 is ordered, it must also show the extra PSL 2 requirements, such as maximum yield and carbon equivalent. A certificate that simply lists the specifications without the corresponding results is incomplete.
Red flags
- Results reported only as "OK" or "Satisfactory"
- A heat number that appears on several unrelated certificates
- Missing signature or authorised inspector for 3.2
- Chemistry exactly at the limit in every element
- Edition years that do not match the project specification
Related guides, comparisons and articles
Frequently asked questions
Is a 3.1 certificate enough for pressure equipment?
Often yes, but many projects and regulations require 3.2 certificates, which add validation by an independent inspector or the purchaser. Check the project specification.
Can a stockist issue a mill test certificate?
The manufacturer issues the original. Stockists supply the original or a certified copy and must keep traceability through cutting and processing.
Should I verify an MTC with PMI?
For alloy materials, PMI on receipt is a quick check that the material matches the certificate. Use OES where carbon must be confirmed.
Does Bright Tubes supply the materials discussed in this article?
Yes. SS 316L Stainless Steel, ASTM A106 Grade B and related products are supplied from stock or mill-sourced, with EN 10204 certificates.
Can I get technical advice for my application?
Yes. Share your service conditions and specification, and our team can help shortlist suitable grades for your engineer to confirm.