Article
Marking is how a pipe, fitting or flange identifies itself. Without correct marking, even perfect material cannot be traced to its test certificate and may be rejected at inspection. Buyers should know what to look for.
Stainless pipe marking (ASTM A312 / A999)
MAKER · ASTM A312 TP316L · 4" SCH40S · SMLS · HT 12345 · HYDRO / ET
- Manufacturer's name or brand
- Specification and grade
- Size and schedule (or OD × wall)
- Seamless or welded
- Heat number
- Test method: hydrostatic test pressure or NDE (for example ET)
Buttweld fitting marking (ASTM A403 / ASME B16.9)
- Manufacturer's name or trademark
- Grade and class, for example WP316L-S
- Size and schedule
- Heat number or heat code
- Symbol "B16" or the standard designation where required
Flange marking (ASME B16.5)
- Manufacturer's name or trademark
- Material, for example ASTM A182 F316L
- Size, class and facing
- Bore or schedule for weld neck flanges
- Ring number for RTJ flanges
- Heat number
Marking methods
| Method | Used on |
|---|---|
| Ink-jet or stencil paint | Pipes, along the length |
| Low-stress die stamping | Fittings and flanges |
| Laser or electro-etching | Thin-wall stainless items |
For stainless steel, inks and paints must be free of chlorides, sulphur and harmful metals so they do not cause corrosion.
Why the heat number matters
The heat number links each item to the chemistry and mechanical test results on the EN 10204 3.1 certificate. At receipt inspection, always match heat numbers on the material with those on the MTC.
Frequently asked questions
What is a heat number?
A unique identifier for a batch of steel from one melt, used to trace material back to its chemical and mechanical test results.
Should stainless pipe be die stamped?
Thin-wall stainless pipe is usually ink-marked; low-stress stamps are used on fittings and flanges.
What should a weld neck flange marking include?
Maker, material, size, class, facing, bore or schedule, and heat number.
Key takeaways
- Marking links every item to its test certificate.
- Check grade, size, schedule, class and heat number.
- Use chloride-free inks on stainless steel.
Need these products?
Sawariya Metal Industries supplies stainless steel pipes, flanges and buttweld pipe fittings from Mumbai to buyers in India and overseas. Send your size, grade, standard and quantity through our enquiry form and we will reply with a clear quotation and the test documents you need. You can also browse our stainless steel pipes, flanges and buttweld fittings.