Pipeline Welding Requirements — API 1104 Qualification and Inspection
Pipeline welding requirements under API 1104 govern 手順資格, 溶接士 試験, production workmanship, and 検査 for oil and gas pipeline construction. 適合 is mandatory under 49 CFR 192 for gas transmission and 49 CFR 195 for hazardous liquid pipelines in the United States.
Regulatory mandate: API 1104 is not optional for regulated pipelines. U.S. DOT regulations incorporate it by reference. A pipeline 溶接 that does not meet API 1104 requirements is a regulatory violation, not just a quality concern. Welders, inspectors, and contractors must understand these requirements before performing or evaluating パイプライン溶接.
Procedure Qualification Requirements
Pipeline WPS qualification under API 1104 Section 5 requires 破壊試験 of test welds: tensile tests, nick-break tests, and guided bend tests. There is no 事前認定WPS path. Variables include pipe diameter, wall 板厚, 継手設計, 溶接工程, 溶加材, シールドガス, and position.
API 1104 Section 5 requires that every 溶接施工法 used on pipeline construction or 補修 be qualified by destructive testing before production welding begins. There is no 事前認定 exemption comparable to D1.1 条項 5 — every pipeline procedure must be tested and documented.
The procedure 仕様書 must define the welding process, base material specification, diameter and wall 厚さ範囲, joint design (開先角度, ルート間隙, ルート面), 溶加材分類, electrical characteristics, position, direction of welding, shielding gas (if applicable), 予熱 and interpass temperatures, 溶接後熱処理 (if applicable), and number and sequence of passes.
Qualification testing requires the 施工業者 to produce a 試験溶接 under controlled conditions, then cut and test specimens from the completed weld. The required destructive tests for butt welds include tensile tests (two specimens), nick-break tests (two specimens from the root and face side), and guided bend tests (two root bends and two face bends for thinner material, or four side bends for wall thickness exceeding 12.7 mm). 放射線透過 or 超音波探傷試験 is performed on the completed test weld before destructive specimen removal.
Welder Qualification Requirements
API 1104 Section 6 qualifies welders on test coupons using the specific WPS they will use in production. 資格試験 includes nick-break and bend tests or radiographic examination. Qualification is specific to pipe diameter ranges, wall thickness ranges, and 溶接姿勢 (fixed, rolled, or combination).
Section 6 requires each welder to demonstrate competence by producing a test weld that meets the 受入基準. The qualification test is specific to the welding procedure, position, and pipe 径範囲. The welder must use the same process, filler metal type, and technique specified in the qualified procedure.
Pipeline welding positions include:
- Rolled (1G)
- Pipe is rotated during welding, so all welding occurs in the flat position. Used for shop 製作 and tie-in welds where rotation equipment is available. A 1G qualification does not qualify for fixed-position field welding.
- Fixed horizontal (5G)
- Pipe axis is horizontal and the pipe cannot be rotated. The welder must weld around the pipe from top to bottom (or bottom to top), passing through vertical and overhead positions. This is the most common field welding position for horizontal pipeline construction.
- Fixed inclined (6G)
- Pipe axis is inclined at 45 degrees and cannot be rotated. This position combines elements of all other positions and is the most comprehensive single-position qualification. A 6G qualification covers all fixed-position welding including 5G, 2G, and restricted-access conditions.
- Restricted access (branch connections)
- Pipeline branch connections and saddle joints present restricted access conditions where 規格 butt weld techniques are insufficient. API 1104
Section 6addresses qualification for these geometries separately. The welder must demonstrate competence in multiple positions with limited access, simulating the real conditions encountered on operating pipeline systems.
Welder qualifications under API 1104 are specific to the employer. A welder changing companies must re-qualify with the new employer, even if the procedure is identical. This is more restrictive than ASME Section IX, where performance qualifications can transfer between employers under certain conditions.
Production Welding Workmanship
API 1104 Section 7 governs production welding. Requirements include surface preparation, alignment and spacing tolerances, weather protection, and interpass cleaning. Tack welds become part of the completed weld and must meet the same quality requirements.
Sections 7 and 8 of API 1104 establish workmanship requirements for production welding. Key provisions include alignment tolerances for butt joints (internal 目違い must not exceed specified 限界値 based on pipe wall thickness), 最小 preheat requirements based on material grade and wall thickness, パス間温度 limits, cleaning requirements between passes, and restrictions on the use of hammering or peening on completed welds.
Pipeline welds are typically made using downhill progression — starting at the 12 o’clock position (top of pipe) and progressing downward to the 6 o’clock position. This differs from structural welding under D1.1, which typically uses uphill progression. Downhill welding requires faster travel speeds and produces lower 入熱 per pass, which affects the resulting ミクロ組織 and 機械的性質 of the 熱影響部. The choice of progression direction is an 重要変数 in the procedure specification.
Root pass welding on pipelines typically uses SMAW with E6010 cellulosic electrodes, producing an open-root joint without バッキング. This technique requires high welder skill to achieve consistent root penetration without 溶落ち or 融合不良. Fill and cap passes may use the same process or transition to FCAW, GMAW, or other processes as specified in the qualified procedure.
Inspection and 合否基準 Criteria
API 1104 Section 8 establishes inspection and testing requirements for production welds, while Section 9 defines the acceptance standards for discontinuities found by those inspections. 外観検査 verifies ビード外観, reinforcement height, and surface defects. 放射線透過試験 evaluates internal defects: inadequate penetration, incomplete fusion, 気孔, slag, and burn-through. Acceptance limits are based on 溶接欠陥 length relative to weld length.
Section 8 of API 1104 establishes inspection requirements; Section 9 establishes the acceptance standards for production welds. All production girth welds must be inspected by radiographic testing (RT), 超音波 testing (UT), or other approved 非破壊検査 methods as specified in the construction documents. 目視 inspection is required for all welds before and during NDT.
The acceptance criteria in Section 9 address specific 不連続 種類 found in pipeline girth welds. Each discontinuity type has defined acceptance limits based on length, width, and distribution relative to the weld length:
- Inadequate penetration without high-low (IP)
- Root penetration must be complete and continuous. Individual IP indications up to 25 mm are acceptable if the total length does not exceed 25 mm in any 300 mm of weld. Total IP in the weld must not exceed 8% of the weld length.
- Incomplete fusion (IF)
- Fusion must be complete between the 溶接金属 and the 母材, and between adjacent weld passes. Acceptance limits for IF are the same as for IP — individual indications up to 25 mm, total not exceeding 25 mm in any 300 mm, and not exceeding 8% of weld length.
- Burn-through (BT)
- Burn-through occurs when the welding arc melts through the pipe wall. Section 9.3.7 defines acceptance criteria for burn-through based on the 最大 dimension of individual indications and their cumulative length relative to the weld length. Individual burn-through areas must not exceed specified サイズ limits.
- Slag inclusions and porosity
- Elongated slag inclusions exceeding 50 mm are not acceptable. Isolated slag inclusions up to 50 mm are acceptable if width does not exceed specified limits. Porosity is evaluated by cluster size and distribution — individual pore diameter must not exceed specified limits, and the total area of porosity in any cluster must not exceed specified percentages.
In-Service Welding
API 1104 Appendix B covers welding on pipelines that are in operation, which may contain pressurized hydrocarbon product. In-service welding includes hot taps (adding branch connections while pressurized), encirclement sleeve installations, and direct deposit weld repairs. The primary safety concern is burn-through — the welding arc melting through the remaining wall thickness into the pressurized product, which can cause a release of flammable or toxic material.
Procedure qualification for in-service welding requires testing under simulated flow conditions at the minimum wall thickness expected in the field. Heat input must be carefully controlled — too high risks burn-through, too low risks 水素割れ due to the rapid cooling caused by flowing product acting as a heat sink. Preheat requirements may differ from new construction procedures because the flowing product reduces the effectiveness of external preheating.
In-service welder qualifications require the welder to demonstrate competence under simulated in-service conditions. The welder must show the ability to control heat input while achieving complete fusion and acceptable root penetration on thin-wall material with cooling conditions that simulate flowing product.
How Pipeline Requirements Compare to Other Codes
API 1104 governs cross-country pipelines with no prequalified WPS path. D1.1 governs steel structures with prequalified WPSs. ASME IX governs pressure equipment (plant piping, vessels). API 1104 groups base metals by specified minimum yield 強度; D1.1 uses 表 5.6 steel grade categories.
D1.1 structural welding focuses on buildings and bridges using plate and shapes, with prequalified WPS exemptions and Table 8.1 acceptance criteria designed for statically and cyclically 読み込み済み connections. Pipeline welding under API 1104 focuses on circumferential butt joints in round pipe, with no prequalified exemptions and acceptance criteria designed for pressurized containment systems. ASME IX provides the qualification framework for pressure vessels and some piping systems, but pipeline-specific regulations reference API 1104 directly. For Canadian pipeline work, CSA Z662 is the governing standard rather than API 1104.
| Aspect | API 1104 | AWS D1.1 | ASME IX |
|---|---|---|---|
| Scope | Cross-country pipelines | Structural steel | Pressure equipment |
| Prequalified WPS? | No | Yes (Clause 5) | No |
| Qualification method | Section 5 destructive testing | Clause 6 testing | QW testing + PQR |
| Base metal grouping | SMYS Groups I–IV | Table 5.6 categories | P-numbers |
| Acceptance criteria | Section 9 + ECA (Appendix A) | Table 8.1 visual | Per construction code |
| In-service welding | Appendix B | Clause 11 (repair only) | Not covered |
Related Standards Guides
"API 1104 is the single governing 基準 for all pipeline welding in the Western Hemisphere. Its incorporation by reference into
— Widely cited in pipeline construction training, reflecting API 1104:2021 and49 CFR 192and49 CFR 195makes compliance a federal regulatory requirement, not a voluntary best practice."49 CFR 192/195
Frequently Asked Questions
API 1104 (Welding of Pipelines and Related Facilities) is the primary welding standard for oil and gas pipelines in the Western Hemisphere. It is incorporated by reference into U.S. Department of Transportation regulations __BODYMASK_20__ (gas transmission pipelines) and __BODYMASK_21__ (hazardous liquid pipelines), making compliance legally mandatory for all regulated pipeline systems in the United States. API 1104 covers the full welding lifecycle: procedure qualification (Section 5), welder qualification (Section 6), production workmanship (Section 7), inspection and testing (Section 8), acceptance standards (Section 9), and in-service welding on live pipelines (Appendix B). For pipelines that also fall under ASME B31.8 (gas transmission) or B31.4 (liquid transportation), API 1104 governs the welding qualification — not ASME Section IX. In Canada, CSA Z662 serves as the equivalent governing standard.
Pipeline welding positions under API 1104 Section 6 include rolled (1G), fixed horizontal (5G), fixed inclined at 45 degrees (6G), and restricted access positions for branch connections. The 6G position is the most comprehensive single qualification because the pipe is fixed at a 45-degree angle, forcing the welder to weld through flat, vertical, and overhead positions in a single continuous test. A 6G qualification covers all fixed-position welding including 5G and 2G. Rolled (1G) qualification only covers the rolled position and is limited to shop fabrication where pipe can be rotated during welding. Most field pipeline welding occurs in the 5G fixed horizontal position. Qualification is employer-specific — unlike ASME Section IX, API 1104 does not allow performance qualifications to transfer between companies. A welder changing employers must re-qualify even if the procedure is identical.
Pipeline welding under API 1104 and structural welding under AWS D1.1 differ in several fundamental ways. Pipeline welds are typically circumferential butt joints on round pipe in fixed positions, while structural welds include groove and fillet welds on plate and shapes in multiple orientations. Pipeline welding predominantly uses downhill progression — starting at the 12 o'clock position and progressing to 6 o'clock — which requires faster travel speeds and produces lower heat input per pass. Structural welding typically uses uphill progression. Pipeline qualification is based on pipe diameter ranges and wall thickness, while D1.1 qualifies by plate thickness. Pipeline root passes commonly use SMAW with E6010 cellulosic electrodes for open-root joints without backing, a technique not prequalified under D1.1. API 1104 has no prequalified WPS path — every procedure must be qualified by destructive testing per Section 5, whereas D1.1 Clause 5 allows prequalified WPSs for common joint configurations.
A pipeline welding coupon test under API 1104 __BODYMASK_22__ requires the welder to produce a complete circumferential butt weld on a pipe test specimen using the qualified welding procedure. The completed test weld is first examined by radiographic testing or ultrasonic testing to detect internal discontinuities. Then destructive test specimens are cut from the weld: nick-break specimens evaluate the weld cross-section for internal defects like porosity and slag, while root bend and face bend specimens verify ductility and fusion. For wall thickness exceeding 12.7 mm (0.500 in), four side bend specimens replace the root and face bends. The test pipe diameter and welding position must match or exceed the intended production work per Section 6.2.1 qualification ranges. Failed specimens require the welder to re-test. The qualification record documents the specific procedure, position, pipe diameter range, and wall thickness range the welder is qualified to weld.
An API 1104 pipeline welder qualification does not automatically qualify the welder for structural steel welding under AWS D1.1, and vice versa. The two standards maintain completely independent qualification systems with different essential variables, test specimen requirements, acceptance criteria, and scope of validity. API 1104 qualifies by pipe diameter and wall thickness ranges; D1.1 qualifies by plate thickness ranges. API 1104 uses nick-break and bend tests; D1.1 uses bend tests and may use fillet weld break tests. A pipeline welder seeking to perform structural work must qualify separately under D1.1 Clause 6 (or the applicable structural code). In practice, many experienced pipeline welders also hold D1.1 structural qualifications, but each certification must be obtained, documented, and maintained independently. The welding skills overlap significantly — particularly in SMAW technique — but the qualification paperwork is entirely separate.