Pipe identification = reading the mill marking on the pipe outer surface to extract key data: brand/logo, standard, grade, size, schedule, heat number, pipe type, batch, length.
Common marking methods
- Ink jet / stencil paint (carbon steel line pipe, black pipe)
- Laser marking (stainless steel, alloy pipe, permanent, no paint)
- Steel stamping / emboss (heavy wall, high pressure pipe; raised characters)
- Tags: bundled small pipes may only have info on metal tags
Where to look for markings
- Along the pipe body - stenciled, inkjet, painted, or laser text
- Near the pipe end - stamped marks, tags, or labels
- On bundle tags - common for small-diameter pipe
- On end caps/protectors - tags sometimes attached
- On coating - FBE/3LPE pipe may have markings on coating or a separate tag
Typical real marking examples
Example 1: SAWH Steel pipe marking
| Brand | Youfa Steel Pipe |
| Standard |
SY/T 5037-2023: Chinese petroleum industry standard for spiral submerged arc welded steel pipes for low-pressure fluid conveyance. |
| Size | OD 426 mm, WT 7 mm, Length 12000 mm |
| Material | GradeQ235B |
| Pipe Type | SAWH (Spiral Submerged Arc Welded) |
| Batch / Heat | No.26#B |
| Pipe Serial No. | 716 |
| TS License No. | 2712382-2028 |
| Status | Factory inspected |
Example 2: bS1387 Steel pipe marking
| Brand | Youfa Steel Pipe |
| Standard |
BS1387: British standard: Specification for screwed, socketed, plain-end carbon steel tubes (widely used for water, air, low-pressure fluid piping) |
| Size | OD 1 1/2", WT 2.5 mm |
| grade | Class A-1:Extra Light / Class A light wall grade under BS1387, thinner wall for low-pressure service. |
The marking is compliant with BS1387:1985.The standard's original marking requirement is only to identify the standard, class, size, manufacturer, plus colour band marking for weight class (Class A / B / C).This standard does not oblige heat number, pipe serial number or ERW mark to be printed on each tube. Traceability heat & batch info will be provided on bundle tags and MTR certificate.
Example 3: UL/FM Steel pipe marking
| Certification |
UL/FM: UL (Underwriters Laboratories) and FM (Factory Mutual) approvals for fire protection piping systems, widely recognized for fire sprinkler projects in North America. |
| Size Category | Schedule 10 |
| Size | OD 2 1/2 inch, WT 3.05mm, Length 6m |
| Pipe Type | Fire Pipe: Fire sprinkler / fire protection pipe. |
| Batch / Heat | No.:YF9421 |
For UL/FM fire pipe, heat number is mandatory (present here: YF9421). Pipe type, batch number and pipe serial number are not required by UL/FM marking rules.They may be shown on bundle tags, packing lists or MTR, not required on the pipe outer wall.
Frequently Asked Questions
Q:What is the most important marking on a steel pipe?
A: The Heat Number (or Melt Number). It is the unique code that links the physical pipe to its Mill Test Report (MTR). Without a heat number, the pipe's chemical and mechanical properties cannot be officially verified.
Q:Can markings be transferred if a pipe is cut?
A: Yes, but the fabricator must strictly follow a "mark transfer" procedure. The new cut piece must be re-marked with the original standard, grade, size, and heat number using durable paint or stamping.
Q:How do I know if the number on the pipe is NPS or Actual OD?
A:NPS (Nominal Pipe Size): Written as a dimensionless number (e.g., NPS 6).
Actual OD (Outside Diameter): Written with inches or mm (e.g., 6.625" OD or 168.3 mm).
Rule of thumb: If the number is a fraction or whole number without decimals (like 6), it's likely NPS. If it has decimals (like 6.625), it's the actual OD.
Q: What is Schedule (SCH)? Why print both SCH and wall thickness (WT)? Are they conflicting?
A: No conflict.
Schedule (SCH10 / SCH40 / SCH80) = ASME B36.10 wall thickness series code. It is a classification system.
The numerical WT (e.g. 3.05 mm) = the actual nominal wall thickness for that specific NPS under this SCH.
Same SCH number has different wall thickness at different nominal sizes.Fire pipe (UL/FM) often prints both for cross-regional reading.
If you have any inquiries and questions, please contact Youfa Steel Pipe. at any time. Thanks in advance. Welcome!
