Specifying the wrong valve standard is one of the most common — and most expensive — procurement mistakes in oil & gas. API 6D and API 600 sound similar and both produce steel valves rated to high pressure, but they govern different applications. Order the wrong one and you risk a valve that is non-compliant for its service, fails inspection, or simply does not fit the system design.
This guide explains what each standard covers, when to use which, and the supporting specifications you should reference on a requisition.
What API 6D covers
API Specification 6D applies to valves used in pipeline transportation systems — the trunk lines that move crude, refined products and natural gas. It is the pipeline counterpart to ASME B31.4 (liquid pipelines) and B31.8 (gas pipelines).
API 6D covers four valve types:
- Ball valves — the workhorse for pipeline isolation; full-bore (full-opening) versions allow pigging.
- Gate valves — through-conduit / slab-gate designs for on/off isolation.
- Check valves — to prevent reverse flow.
- Plug valves — for isolation and, in some configurations, throttling.
Key features the standard addresses: pressure-temperature ratings (per ASME B16.34), full-bore vs reduced-bore configuration, antistatic devices, drain and vent connections, double block-and-bleed capability, and pressure testing.
What API 600 covers
API Standard 600 applies to bolted-bonnet steel gate valves for the petroleum and natural gas industries — typically process, refinery and plant service rather than cross-country pipelines. These are flanged or butt-welding gate valves built for tight shut-off and infrequent operation.
API 600 governs wall thickness, stem design, backseat, bonnet bolting, trim materials and marking. For small-bore gate valves (generally NPS 4 and smaller) the related standard API 602 covers compact forged-steel designs, which are usually more economical and robust at small sizes.
Quick comparison
| API 6D | API 600 | |
|---|---|---|
| Primary application | Pipeline transportation | Refinery / process plant |
| Design code reference | ASME B31.4 / B31.8 | ASME B16.34 |
| Valve types | Ball, gate, check, plug | Bolted-bonnet gate |
| Typical service | Isolation, pigging, block & bleed | Tight shut-off, isolation |
| Bore | Often full-bore for pigging | Full port through-conduit |
| Small-bore alternative | — | API 602 (forged, ≤ NPS 4) |
Other standards you'll see on the same requisition
Valves rarely arrive specified by a single number. Expect to reference:
- ASME B16.34 — the umbrella pressure-temperature rating standard (Class 150 to 2500).
- ASME B16.5 / B16.47 — flange dimensions and ratings.
- API 594 / API 6D — check valves.
- API 609 — butterfly valves.
- API 623 — bolted-bonnet steel globe valves.
- API 526 — flanged steel pressure-relief valves.
- API 607 / API 6FA — fire test for soft-seated and metal-seated valves.
- API 641 / API 624 — fugitive-emission (low-leak) testing of quarter-turn and rising-stem valves.
How to specify correctly
A complete valve line item should state, at minimum:
- Valve type and standard (e.g. "ball valve, API 6D").
- Size and pressure class (e.g. NPS 6, Class 600).
- End connections (RF flanged, RTJ, butt-weld).
- Body and trim materials (e.g. body ASTM A216 WCB; trim 13Cr or stainless).
- Bore (full vs reduced).
- Operation (lever, gear, actuator — pneumatic/electric).
- Special requirements (fire-safe, fugitive-emission certified, NACE MR0175 / ISO 15156 for sour service).
For sour service (H₂S present), NACE MR0175 / ISO 15156 material compliance is critical and should be called out explicitly — it constrains the body, trim and bolting metallurgy.
Buying valves in Nigeria
Lead time and certification are usually the deciding factors. When sourcing, insist on:
- Material test certificates (MTCs) to EN 10204 3.1 traceability.
- Pressure-test and, where required, fire-test certificates.
- NACE compliance documentation for sour service.
FirstSupply.ng supplies API-rated ball, gate, globe, check, butterfly and control valves with the supporting documentation, priced in Naira with delivery from Lagos and Port Harcourt. If you have a valve datasheet or line list, send it with a quote request and we will match the correct standard, class and metallurgy.