1.1 Scope, Definitions & General Requirements

1.1 Scope, Definitions & General Requirements

API Standard 1104, titled Welding of Pipelines and Related Facilities, is the premier industry standard governing field welding for cross-country transmission pipelines and related infrastructure. First published in 1953 as a joint effort by the American Petroleum Institute (API) and the American Welding Society (AWS), API 1104 has evolved through twenty-two major revisions to reflect modern metallurgical, welding, and non-destructive examination (NDE) technologies. Candidates preparing for the AWS Certified Welding Inspector (CWI) Endorsement exam on API 1104 (22nd Edition, 2021) must master not only the explicit technical rules within the standard but also its regulatory context, code structure, and fundamental terminology.

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1. Industry Scope and Application Limits

API Standard 1104 applies specifically to the gas and arc welding of butt joints, fillet joints, and socket joints in carbon steel and low-alloy steel piping. The piping systems covered by this standard are those utilized in the compression, pumping, and transmission of:

• Crude Petroleum: Unrefined liquid hydrocarbons transported from production fields to refineries.
• Petroleum Products: Refined liquid fuels including gasoline, diesel, jet fuel, and natural gas liquids (NGLs).
• Fuel Gases: Natural gas (methane), synthetic natural gas, propane, and butane.
• Carbon Dioxide (CO_2): Supercritical and gaseous carbon dioxide used for enhanced oil recovery (EOR) and carbon capture/sequestration.
• Nitrogen (N_2): Inert gases used in industrial transmission and pressure testing.

Application Envelope

The scope of API 1104 (22nd Edition) is defined by product, material, and process — not by a temperature or pressure range. The standard covers butt, branch, and fillet welds in carbon and low-alloy steel pipe and piping components, applies to both new construction and in-service welding, and permits the SMAW, SAW, GTAW, GMAW, FCAW, PAW, and oxyacetylene (OFW) processes used with manual, semiautomatic, or mechanized techniques in position or roll welding. Service limits such as design temperature, pressure, and product containment come from the governing design codes (ASME B31.4 / B31.8) and federal regulation, not from API 1104 itself.

Infrastructure Facilities

The physical facilities encompassed by API 1104 extend beyond the continuous cross-country mainline pipe. The scope explicitly covers:

1. Cross-Country Transmission Pipelines: Mainline pipe strings, loop lines, tie-ins, and river crossings.
2. Pumping Stations: Liquid hydrocarbon pressurization facilities, manifold piping, pump headers, and meter runs.
3. Compressor Stations: Natural gas compression facilities, suction/discharge headers, scrubbers, and fuel gas piping.
4. Meter and Regulating (M&R) Stations: Pressure reduction manifolds, custody transfer metering runs, and control valve assemblies.

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2. Regulatory Hierarchy and Reference Standards

API 1104 does not exist in a regulatory vacuum; it is incorporated by reference into federal law and overarching engineering design codes. Understanding this hierarchy is essential for welding inspectors.

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|               Federal Regulations (49 CFR 192 / 195)              |
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|               Design Codes (ASME B31.4 / ASME B31.8)              |
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|            Construction Standard (API Standard 1104)             |
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|         Material & Filler Specs (API 5L / AWS A5 Series)          |
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Federal Regulations (49 CFR)

In the United States, the Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) enforces safety standards codified in the Code of Federal Regulations (CFR):

• 49 CFR Part 192: Transportation of Natural and Other Gas by Pipeline: Minimum Federal Safety Standards.
• 49 CFR Part 195: Transportation of Hazardous Liquids by Pipeline.

Both Part 192 and Part 195 mandate that welding of steel pipelines must be performed in accordance with API 1104 or ASME Section IX.

ASME B31 Code Series

API 1104 serves as the primary welding specification referenced by ASME piping design codes:

• ASME B31.4: Pipeline Transportation Systems for Liquids and Slurries. Governs liquid pipeline design, construction, inspection, and testing.
• ASME B31.8: Gas Transmission and Distribution Piping Systems. Governs natural gas gathering, transmission, and distribution piping.

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3. Key Terminology and Essential Definitions

Accurate interpretation of API 1104 requires precise knowledge of code-defined terms:

• Welding Procedure Specification (WPS): A detailed written document containing all required parameters and essential variables to guide welders in making sound production welds.
• Procedure Qualification Record (PQR): A certified record of the actual variables recorded during the welding of a test coupon and the subsequent quantitative mechanical test results used to qualify a WPS.
• Welder Qualification Test Record (WQTR): A formal record verifying that an individual welder has successfully completed a qualification test demonstrating the skill required to produce sound welds under a qualified WPS.
• Specified Minimum Yield Strength (SMYS): The minimum yield strength prescribed by the base metal manufacturing specification (e.g., API 5L Grade X65 has an SMYS of 65,000 psi).
• Essential Variable: A parameter in a WPS or welder qualification that, when changed beyond code-specified limits, alters the mechanical properties or quality of the weld, thereby requiring requalification.
• Company: The operating owner company or the engineering agency acting on behalf of the owner.
• Contractor: The welding or pipeline construction contractor responsible for performing welding operations.

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4. Equipment Requirements and Calibration

Section 4 of API 1104 specifies stringent operational standards for field welding equipment:

1. Equipment Condition: All welding equipment (arc welding generators, rectifiers, inverters, wire feeders, and oxyfuel cutting/welding apparatus) must be maintained in safe operating condition. Equipment displaying excessive wear, electrical instability, or gas leakage must be removed from service.
2. Operating Parameters: Equipment must operate smoothly across the voltage, amperage, and travel speed ranges specified in the qualified WPS.
3. Calibration & Verification: Ammeters, voltmeters, wire feed speed meters, and temperature-indicating crayons/pyrometers used during WPS qualification and production welding must undergo regular calibration against certified reference standards.

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5. Structural Organization of the API 1104 Standard

API 1104 (22nd Edition) is organized into twelve core sections and three normative annexes — Annex A (Alternative Acceptance Standards for Girth Welds, the fracture-mechanics ECA route), Annex B (In-service Welding), and Annex C (Requests for Interpretation and Revision). Below is a comparative structural overview highlighting key differences between API 1104, AWS D1.1 (Structural Steel), and ASME Section IX (Boiler & Pressure Vessel Code):

Understanding this structural organization enables the Certified Welding Inspector to rapidly navigate the code during open-book examination scenarios and enforce quality control standards in the field.