Piping enquiries arrive under-specified in the same three places, every time: the grade, the schedule and the certificate. Each omission has the same effect — the supplier either guesses, or asks, and both cost days. This guide covers what a pipe, fitting or flange line has to state to be priced accurately the first time.
The short answer: a piping line item needs the governing specification and grade (e.g. ASTM A106 Grade B), the nominal size and schedule (e.g. NPS 6, Sch 40), the manufacturing route where it matters (seamless or welded), the end preparation, and the material certification required (typically EN 10204 3.1). Anything less is a request for a guess.
Carbon steel: A106, A53 and API 5L
Three specifications cover most carbon-steel pipe bought in Nigeria, and they are not interchangeable.
| Specification | What it is for | Notes |
|---|---|---|
| ASTM A106 | Seamless carbon steel pipe for high-temperature service | Grades A, B, C by strength. Grade B is the process-piping workhorse |
| ASTM A53 | Welded and seamless pipe, general and mechanical service | Types E (ERW), S (seamless); Grades A and B. Lower duty than A106 |
| API 5L | Line pipe for oil and gas transmission | Graded by yield: X42, X52, X65, etc. PSL 1 and PSL 2 quality levels |
Pipe is sometimes dual-certified — the same length meeting A106 Grade B and API 5L, for example. This is genuinely useful, but it is a property of that specific heat of material, evidenced on the mill certificate. Treat a supplier's claim of dual certification as something to verify on the paperwork, not as a general property of the product.
For sour service — where H₂S is present — the governing constraint is NACE MR0175 / ISO 15156, which limits hardness and constrains the chemistry. Call it out explicitly on the line; it is not implied by any of the three specifications above.
Stainless: A312 and the L grades
ASTM A312 covers seamless and welded austenitic stainless pipe, most commonly TP304/304L and TP316/316L.
The L suffix means low carbon. It matters for welding: lower carbon reduces the precipitation of chromium carbides at grain boundaries in the heat-affected zone, which is what causes sensitisation and subsequent intergranular corrosion. If the pipe is going to be welded and then see a corrosive service, specify the L grade. 316L additionally contains molybdenum, giving markedly better resistance to chlorides than 304 — which is why it is the default for marine and coastal installations, and for much of the Niger Delta.
For instrument tubing — as distinct from pipe — the relevant specification is usually ASTM A269 or A213, and the size is an actual outside diameter (⅜", ½") rather than an NPS. Confusing tubing with small-bore pipe is one of the more expensive ordering mistakes, because the fittings do not interchange.
Size and schedule
Nominal Pipe Size (NPS) is not a measurement. For NPS 12 and below it is a designation only; the actual outside diameter differs from the number. What the OD is fixed by NPS, which is why schedule — the wall thickness designation — completes the specification.
Because OD is fixed, a higher schedule eats into the bore. A NPS 6 Sch 80 pipe has the same outside diameter as NPS 6 Sch 40 but a thicker wall, a smaller internal diameter and a higher pressure rating. Specify both: NPS 6, Sch 40 is a pipe; 6 inch pipe is a question.
Fittings and flanges
Fittings follow the pipe. Buttweld fittings to ASME B16.9 are matched to the pipe schedule so the bores line up at the weld; forged fittings to ASME B16.11 are rated by class (3000, 6000, 9000) and come socket-weld or threaded. The material specification for forged carbon-steel fittings is typically ASTM A105; for stainless, ASTM A182 with the appropriate grade (F304L, F316L).
Flanges are defined by four things:
- Size and pressure class — Class 150, 300, 600, 900, 1500, 2500 to ASME B16.5 (up to NPS 24) or B16.47 above that.
- Type — weld neck, slip-on, socket weld, threaded, lap joint, blind.
- Facing — raised face (RF), flat face (FF) or ring-type joint (RTJ). This determines the gasket, so it cannot be left off.
- Material — A105 for carbon steel, A182 F-grades for stainless and alloy.
A pressure class is not a pressure. The actual allowable working pressure for a given class falls as temperature rises, per the pressure–temperature rating tables in ASME B16.5. A Class 300 flange does not hold 300 of anything; read the table for your design temperature.
Whatever the flange, the joint is completed by a gasket — and that is where flanged joints most often leak. See spiral-wound gaskets and flange sealing for how to specify one, and hydraulic torque wrench selection for getting the bolt load right.
The certificate is part of the specification
For pressure-containing piping, the material certificate is not paperwork attached to the goods — it is part of what you bought. EN 10204 defines the types:
| Type | Issued by | What it says |
|---|---|---|
| 2.1 | Manufacturer | Declaration of compliance, no test results |
| 2.2 | Manufacturer | Compliance plus non-specific test results |
| 3.1 | Manufacturer's authorised inspection representative, independent of production | Compliance plus actual test results for that heat |
| 3.2 | Manufacturer and an independent third party or purchaser's inspector | As 3.1, countersigned by an independent witness |
For most oil & gas and process work in Nigeria, 3.1 is the requirement. Two practical consequences:
- Ask on the enquiry, not on the purchase order. Certification affects which mill and which heat can supply the line. Adding the requirement after the material is made is usually impossible.
- 3.2 must be arranged before manufacture. It requires an independent inspector present at testing. It cannot be issued retrospectively, and a supplier who offers to "get you a 3.2" for material already produced is describing something that does not exist.
Where the material is imported, the certificate also travels with the shipment — see importing certified industrial equipment into Nigeria for the documents that accompany a consignment.
Buying piping in Nigeria
Piping splits cleanly into two commercial cases, and the split is worth making line by line:
- Commodity sizes in common grades — A106 Grade B, standard schedules, common flange classes — are frequently available from Nigerian stock. Buying locally means naira pricing, no duty, no clearing, and days rather than weeks.
- Specified, certified or alloy material — sour-service grades, higher alloys, unusual sizes, anything with a demanding certification requirement — is generally imported to order.
A supplier who does both can quote each line on whichever route is genuinely cheaper delivered, rather than forcing the whole schedule down one path. That is the comparison worth asking for.
FirstSupply quotes carbon, stainless and alloy piping, fittings, flanges and fasteners to specification, with the certification stated on the quotation. Browse pipe, fittings & flanges, or send us the line list or isometric take-off and we will price it item by item — and tell you which lines are better bought in-country.