A buyer’s guide to flange forgings: forging, machining, testing
What ASME B16.5 actually guarantees, what the mill certificate proves, and the three tests worth paying for.
Flange forgings look identical on a datasheet and very different in service. Here is what separates them.
What ASME B16.5 guarantees
The standard fixes dimensions, ratings and materials — it does not guarantee the steel itself. That is the job of the mill certificate and the heat number stamped on the flange face. Without a heat number that leads to a document, the flange is a guess.
Three tests worth paying for
- Ultrasonic testing (ASTM A388) — finds internal voids and laminations before machining wastes hours
- Hydrostatic testing (API 598) — proves the pressure boundary at 1.5× rating
- Positive material identification — confirms the alloy, not just the paperwork
We run all three routinely and the heat number on your flange leads to a certificate, not a shrug. EN 10204 3.1 is standard; 3.2 inspection at the mill can be arranged.