Components are specified as a set. A carbon steel line for high-temperature service does not just need “a flange” — it needs the flange spec that belongs with that pipe spec. When an MTR does not fit the family, that is the finding.
| Service | Pipe | Butt-weld fittings | Flanges / forgings | Bolting | Nuts |
|---|---|---|---|---|---|
| Carbon steel high temp |
A106 Gr B A53 Gr B |
A234 WPB | A105 | A193 B7 | A194 2H |
| Carbon steel low temp |
A333 Gr 6 | A420 WPL6 | A350 LF2 | A320 L7 | A194 Gr 7 |
| Stainless 304 / 304L |
A312 TP304/304L | A403 WP304/304L | A182 F304/F304L | A193 B8 | A194 Gr 8 |
| Stainless 316 / 316L |
A312 TP316/316L | A403 WP316/316L | A182 F316/F316L | A193 B8M | A194 Gr 8M |
| Chrome-moly elevated temp |
A335 P11 / P22 | A234 WP11 / WP22 | A182 F11 / F22 | A193 B16 | A194 Gr 4 / 7 |
| Duplex 2205 |
A790 S31803/S32205 | A815 WP S31803 | A182 F51 / F60 | A193 B8M* | A194 8M* |
| Line pipe transmission |
API 5L Gr B, X42–X70 | MSS SP-75 WPHY | A694 F42–F70 | A193 B7 | A194 2H |
* Duplex bolting is frequently specified separately — check the project spec rather than assuming the austenitic grade carries over.
| You see | It means |
|---|---|
| A106 Gr B | Seamless CS pipe, high-temp service. Gr B is the common one; A and C also exist. |
| A53 Type E / S | E = electric resistance welded, S = seamless. Type F is furnace butt weld — rarely acceptable. |
| TP304L / F316L | L = low carbon. Better weldability and corrosion resistance at the weld. Not interchangeable with the non-L grade unless the spec says so. |
| A312 TP316 | TP = tube/pipe product form. |
| A403 WP316 | WP = wrought pipe fitting. |
| A182 F316 | F = forging. |
| You see | It means |
|---|---|
| X52, X65 | API 5L line pipe. The number is the specified minimum yield in ksi. |
| PSL 1 / PSL 2 | API 5L product specification level. PSL 2 carries tighter chemistry, testing and documentation. Not interchangeable. |
| A193 B7 / B7M | M = lower hardness, for sour or NACE service. Different bolt, different MTR. |
| A194 2H | The nut normally paired with B7 studs. |
| A420 WPL6 | Low-temperature fitting. The pairing partner for A333 Gr 6 pipe. |
| NACE MR0175 ISO 15156 | Sour service. Drives hardness limits on nearly every component — if it is on the line class, check every MTR against it. |
The material spec says what it is made of. These say what shape it is and what it is rated for. Both appear on a submittal and both get checked.
| Standard | Covers |
|---|---|
| ASME B16.5 | Pipe flanges and flanged fittings, NPS ½ through 24 |
| ASME B16.47 | Large diameter flanges, NPS 26 and above. Series A and Series B are not interchangeable. |
| ASME B16.9 | Factory-made wrought butt-welding fittings |
| ASME B16.11 | Forged fittings — socket weld and threaded |
| ASME B16.20 | Metallic gaskets — spiral wound, jacketed, ring joint |
| ASME B16.21 | Non-metallic flat gaskets |
| ASME B16.34 | Valves — flanged, threaded and welding end |
| ASME B36.10M B36.19M | Welded and seamless wrought steel pipe dimensions / stainless steel pipe dimensions |
| Standard | Covers |
|---|---|
| ASME B31.3 | Process piping — plants, refineries, facilities |
| ASME B31.4 | Pipeline transportation, liquids and slurries |
| ASME B31.8 | Gas transmission and distribution piping |
| API 5L | Line pipe |
| API 6D | Pipeline and piping valves |
| API 1104 | Welding of pipelines and related facilities |
| ASME Sec IX | Welding and brazing qualification, referenced by B31.3 |
| MSS SP-75 | High-test wrought butt-welding fittings for line pipe |
| Pressure classes | Note |
|---|---|
| 150, 300, 400, 600, 900, 1500, 2500 | A class is not a pressure. The actual rating depends on material and temperature — read it off the rating table in B16.5 for that material group. |
| Facing | Where you see it |
|---|---|
| RF — raised face | The default on most CS and SS piping |
| FF — flat face | Typically against cast iron or non-metallic equipment |
| RTJ — ring type joint | Higher pressure and temperature; needs a matching ring groove and gasket |
Two minutes at receipt, against a week-long chase at turnover.
| Check | Why it matters |
|---|---|
| Spec and grade match the requisition | Compare against the line class, not against what you expected to arrive. A106 Gr B and A53 Gr B are different specs even where both are acceptable. |
| Heat number on the certificate matches the marking on the material | The one everybody assumes and nobody checks. If they do not match, nothing downstream is traceable. |
| The certificate is legible and complete | A third-generation scan is not a certificate. Ask for a clean copy while the vendor still has the order open. |
| Product form is right | TP is pipe, WP is a fitting, F is a forging. A certificate for the wrong form is the wrong certificate. |
| Supplementary requirements are present | NACE / sour service, impact testing, PMI, positive material identification — if the line class calls for it, the MTR has to show it. |
| It is the right revision of the spec | Your contract names an edition. A certificate to an older edition may still be fine, but it is a question to ask now, not at handover. |