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What Is API 1104?

API 1104 governs welding of cross-country pipelines and related facilities. It covers carbon and low-alloy steel pipe used in compression, pumping, and transmission of crude petroleum, petroleum products, fuel gases, and carbon dioxide. The 22nd edition (2021) is the current version.

API Standard 1104, “Welding of Pipelines and Related Facilities,” covers the welding of piping used in compression, pumping, and transmission of crude petroleum, petroleum products, fuel gases, carbon dioxide, and nitrogen. The standard applies to both new construction and in-service Reparación welding on pressurized systems. It addresses Soldadura por Arco and oxyfuel gas welding of butt, branch, and fillet welds in carbon and low-alloy steel pipe.

The standard is organized into twelve sections. Sections 1 through 4 cover scope, references, definitions, and specifications. Section 5 establishes Calificación de procedimiento requirements. Section 6 covers Soldador qualification. Section 7 addresses design and preparation of joints for production welding. Section 8 covers inspection and Ensayo of production welds. Section 9 provides Aceptación standards for nondestructive testing. Section 10 covers repair and removal of defects. Section 11 defines procedures for nondestructive testing (NDT). Section 12 covers mechanized welding with Metal de Aporte additions.

The current edition is API 1104, 22nd Edition, 2021. API 1104 is developed independently from both ASME Section IX and AWS D1.1, though many fabricators and pipeline contractors maintain qualifications under multiple standards depending on the jurisdictional requirements of their projects.

Procedure Qualification Under API 1104

API 1104 Section 5 requires every WPS to be qualified by testing. There is no EPS precalificada path. The Fabricante produces test welds on pipe specimens matching the intended production diameter and wall Rango de espesor. Ensayo destructivo includes tensile, nick-break, and bend tests. Ensayo radiográfico may substitute for some destructive tests.

API 1104 Section 5 requires that welding procedures be qualified by destructive testing before production welding begins. The qualification process requires producing test welds on pipe specimens using the intended procedure, then cutting and testing specimens to demonstrate adequate Propiedades mecánicas.

The required destructive tests for butt welds include two tensile specimens, two nick-break specimens, and either root bend plus face bend tests (for thinner walls) or four side bend specimens (for wall Espesor over 12.7 mm). The Soldadura de prueba must also pass either Radiográfico testing or Ensayo ultrasónico before destructive specimen removal.

API 1104 defines essential variables that govern when re-qualification is required. The essential variables specific to API 1104 include:

Welding process

A change in Proceso de Soldadura or combination of processes requires a new qualification. SMAW, GMAW, FCAW, GTAW, and SAW are the commonly qualified processes for pipeline applications. Combinations such as GTAW root with SMAW fill are qualified as a single procedure.

Base metal group

API 1104 groups base metals by specified Mínimo yield Resistencia (SMYS). A procedure qualified on a material in one SMYS group may have limited applicability to materials in other groups. This differs from ASME IX P-numbers, which group by composition and Soldabilidad rather than strength alone.

Joint design

Changes in Diseño de junta beyond the qualified range — including Ángulo de ranura, Apertura de raíz, and Cara de raíz — require re-qualification. Pipeline joints are typically Ranura en V or compound bevel configurations sized for the pipe wall thickness.

Wall thickness range

The qualified wall thickness range is determined by the Cupón de prueba thickness. Qualification on thinner material does not automatically qualify thicker material. The qualified range is specified in Section 5.4 based on the test Soldadura dimensions.

Pipe diameter range

Qualification is limited by the test coupon diameter. The diameter ranges are specified in Section 5.4. Qualification on larger diameters may cover smaller diameters within the specified range, but not vice versa without separate testing.

Position

Pipeline welding positions are designated as rolled (1G), fixed horizontal (5G), fixed inclined (6G), or multiple positions. Qualification in the 6G position qualifies all fixed-position welding. Rolled-position qualification does not qualify fixed positions.

Welder Qualification Under API 1104

API 1104 Section 6 requires each welder to qualify on a test coupon using the specific WPS they will use in production. Qualification variables include pipe diameter, wall thickness, Posición de soldadura, and joint design. Qualification tests include destructive testing (nick-break and bend tests) or radiographic examination of the completed test weld.

Section 6 requires each welder to demonstrate the ability to produce sound welds using the qualified procedure. The welder qualification test produces a test coupon that is examined by radiography or destructive testing. Single-qualification tests qualify the welder for the specific procedure, position, and pipe diameter group tested.

Welder qualifications are specific to the employer. A welder who changes employers must re-qualify with the new company, even if the Procedimiento de soldadura is identical. This is stricter than ASME Section IX, where performance qualifications can transfer between employers under certain conditions. API 1104 welder qualifications do not expire due to inactivity, but the company must have records demonstrating the welder has used the process within the required timeframe.

In-Service Welding (Appendix B)

API 1104 Appendix B covers welding on pipelines that are in service — carrying product under pressure during welding. In-service welding requires additional precautions: Perforación por quemado Prevención (minimum wall thickness verification), Fisuración por hidrógeno prevention (Bajo Hidrógeno processes), and flow rate consideration to manage heat dissipation.

API 1104 Appendix B addresses welding on pipelines that are in operation and may contain pressurized product. In-service welding includes hot taps (adding branch connections while the pipeline is pressurized), encirclement sleeves, and direct deposit repairs. The primary safety concern is burn-through — the welding arc melting through the remaining pipe wall into the pressurized product.

Procedure qualification for in-service welding requires testing at simulated flow conditions to demonstrate the procedure can be safely performed at the minimum wall thickness encountered in the field. Aporte Térmico control is critical — low heat input reduces the risk of burn-through but increases the risk of hydrogen cracking in the Zona Afectada por el Calor. Precalentamiento requirements for in-service welding may differ from new construction because the flowing product acts as a heat sink, increasing cooling rates and hydrogen cracking susceptibility.

How API 1104 Compares to Other Welding Codes

API 1104 governs pipelines; D1.1 governs steel structures; ASME IX governs pressure equipment. API 1104 has no Precalificado WPS path. It classifies filler metals into groups (Tabla 2) and qualifies procedures by pipe diameter and wall thickness ranges. Criterios de aceptación include both workmanship-based Límites (Section 9) and fitness-for-service methods (Appendix A).

API 1104 vs AWS D1.1

D1.1 applies to Acero estructural, while API 1104 applies to pipelines. D1.1 qualifies procedures by plate thickness, while API 1104 qualifies by pipe diameter and wall thickness. D1.1 allows prequalified WPSs under Cláusula 5, while API 1104 requires Ensayo de calificación for every procedure. D1.1 uses Table 5.6 Metal Base groups, while API 1104 groups by SMYS. The acceptance criteria in API 1104 Section 9 are specific to girth welds in pipe, while D1.1 Table 8.1 criteria are for structural connections.

API 1104 vs ASME Section IX

Both standards require procedure qualification testing, but the Variable esencial rules and test requirements differ. ASME IX uses P-numbers for base metal grouping, while API 1104 uses SMYS-based groups. ASME IX guided bend and tension tests differ from API 1104 nick-break and root/face bend tests. When a pipeline also falls under ASME B31.8 (gas transmission) or B31.4 (liquid transportation), the relationship between API 1104 and ASME Section IX must be carefully managed — B31.8 references API 1104 directly for welding qualification, not ASME IX.

Acceptance Standards for NDT

API 1104 Section 9 defines acceptance criteria for radiographic, Partículas Magnéticas, liquid Líquidos Penetrantes, and Ultrasónico testing of production welds. Section 9 provides specific criteria for inadequate penetration, Fusión incompleta, internal concavity, burn-through, slag inclusions, and Porosidad. The acceptance criteria are based on the length and distribution of indications relative to the weld length and pipe wall thickness.

API 1104 also includes provisions for alternative acceptance criteria in Appendix A, which allows engineering critical assessment (ECA) methods based on fracture mechanics. Under Appendix A, Defecto acceptance is based on fitness-for-service analysis rather than workmanship-based limits, potentially allowing larger defects when stress analysis demonstrates the defect will not grow to critical Tamaño during the design life of the pipeline.

"Pipeline welding is unique because you can't rotate the pipe on most field joints — the welder must qualify in the fixed position, welding uphill or downhill around the full circumference. That's why API 1104 qualification is position-specific in a way that D1.1 isn't."

— Field observation, pipeline construction practice

Related Standards Guides

• ASME Section IX — Welding Qualification
• CSA W59 — Welded Steel Construction
• CSA W47.1 — Company Certification
• ASME IX P-Numbers Guide
• ASME IX F-Numbers Guide
• Pipeline Welding Requirements
• WPS — Welding Procedure Specification
• PQR — Procedure Qualification Record
• NDE Requirements — D1.1 Clause 8 inspection methods
• D1.1 Preheat Calculator
• AWS D1.4 — Reinforcing Steel
• AWS D1.6 — Stainless Steel
• AWS D1.8 — Seismic Supplement
• AWS D1.2 — Aluminum
• AWS D1.9 — Titanium
• AWS D1.3 — Sheet Steel
• D1.5 Bridge Preheat Calculator
• AWS D1.5 — Bridge Welding Code
• AS/NZS 1554 — Soldadura de Acero Estructural (Australian Standard)