Oil and gas pipelines – sourcing line pipe, fittings, flanges and valves
In short: oil and gas pipelines need line pipe to EN ISO 3183 or API 5L, in the required strength class (e.g. L360NE / X52) and product level (PSL1 / PSL2). They also need:
- high-yield fittings (ASTM A860 WPHY);
- flanges (A105N, A694 F42 – F70) with RF or RTJ facing;
- API valves rated for the line.
This guide is for gas distribution and transmission companies, oil and gas contractors and buyers.
What makes hydrocarbon pipelines special?
- Regulated environment. Gas pipelines are subject to strict technical regulations and operator specifications.
- Strength and weldability. Higher-strength steel allows thinner walls, but the welding procedure and fittings must match it.
- Toughness and low temperature. The delivery condition (N, Q, M) and PSL2 requirements also govern toughness.
- Corrosion protection. Buried lines are protected by external coating and cathodic protection.
Material overview
| Component | Typical material / standard |
|---|---|
| Line pipe | EN ISO 3183: L245NE – L485ME; API 5L: Gr. B, X42 – X70 (PSL1 / PSL2) |
| Fittings | ASTM A234 WPB; ASTM A860 WPHY 42 – 70; EN 10253-2 |
| Flanges | ASTM A105N; ASTM A694 F42 – F70; A350 LF2 for low temperature |
| Gaskets | Flat gaskets for RF flanges, RTJ gaskets for RTJ flanges, per rating |
| Bolting | Elevated- or low-temperature studs and nuts |
| Valves | API 600 / 602 / 594, ball valves; WCB or LCB bodies |
The operator's specification sets the exact strength class, PSL level and test requirements.
The complete package
- Line pipe seamless or welded, with external PE / PP coating and bevelled ends.
- Fittings: elbows, tees, reducers and caps matched to the pipe's strength class.
- Flanges: weld-neck, blind and orifice flanges, RF or RTJ.
- Forged fittings and olets for instrument and drain connections.
- Gaskets and bolting per pressure rating.
- Valves: gate, ball and check valves to API.
- Anodes for cathodic protection.
Buyer checklist
- Standard and strength class: e.g. EN ISO 3183 L360NE or API 5L X52.
- PSL1 or PSL2.
- Size: OD × wall.
- Manufacturing route: seamless or welded.
- Coating: external and internal, if required.
- Fittings and flanges: material, rating, facing (RF / RTJ).
- Certificate: 3.1 or 3.2.
Common mistakes
- Fitting strength does not match the high-yield pipe.
- Mixing RF and RTJ flanges.
- PSL level not stated, so quotes cannot be compared.
- Uncoated pipe for buried sections.
Frequently asked questions
What is the difference between PSL1 and PSL2?
PSL2 sets stricter chemistry, mechanical and testing requirements, and makes impact testing mandatory. It is requested for more critical pipelines.
Are L360NE and X52 interchangeable?
They denote a similar strength level, but in two different standard systems. Source the designation given in the design.
Do you supply valves too?
Yes. We supply API gate, globe and check valves and ball valves.
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Related: Line pipes · Butt-weld fittings · Flanges · Valves · Expansion joints, anodes
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