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ASME B31.3 Scope

ASME B31.3 Scope


  2. Identification. This Process Piping Code is a Section of the American Society of Mechanical Engineers Code for Pressure Piping, ASME B31, an American National Standard. It is published as a separate document for convenience of Code users.

  3. Responsibilities

  4. Owner. The owner of a piping installation shall have overall responsibility for compliance with this Code, and for establishing the requirements for design, construction, examination, inspection, and testing that will govern the entire fluid handling or process installation of which the piping is a part. The owner is also responsible for designating piping in Category D, Category M, High Pressure, and High Purity Fluid Services, and for determining if a specific Quality System is to be employed. [See paras. 300(d)(4) through and Appendix Q.] Where applicable, the owner shall consider requirements imposed by the authority having jurisdiction regarding the piping installation.

  5. Designer. The designer is responsible to the owner for assurance that the engineering design of piping complies with the requirements of this Code and with any additional requirements established by the owner.

  6. Manufacturer, Fabricator, and Erector. The manufacturer, fabricator, and erector of piping are responsible for providing materials, components, and workmanship in compliance with the requirements of this Code and of the engineering design.

  7. Owner’s Inspector. The owner’s Inspector (see para. 340) is responsible to the owner for ensuring that the requirements of this Code for inspection, examination, and testing are met. If a Quality System is specified by the owner to be employed, the owner’s Inspector is responsible for verifying that it is implemented.

  8. Intent of the Code

  9. It is the intent of this Code to set forth engineering requirements deemed necessary for safe design and construction of piping installations.

  10. This Code is not intended to apply to the operation, examination, inspection, testing, maintenance, or repair of piping that has been placed in service. The provisions of this Code may optionally be applied for those purposes, although other considerations may also be necessary.

  11. The Code generally employs a simplified approach for many of its requirements. A designer capable of applying a more complete and rigorous analysis consistent with the design criteria of this Code shall have the latitude of applying such analysis in the development of designs and fabrications. The designer shall provide details of design, construction, examination, and testing, along with calculations consistent with the design criteria of this Code. The details shall be documented in the engineering design and their validity accepted by the owner.

  12. Piping elements should, insofar as practicable, conform to the specifications and standards listed in this Code. Piping elements neither specifically approved nor specifically prohibited by this Code may be used provided they are qualified for use as set forth in applicable Chapters of this Code.

  13. The engineering design shall specify any unusual requirements for a particular service. Where service requirements necessitate measures beyond those required by this Code, such measures shall be specified by the engineering design. Where so specified, the Code requires that they be accomplished.

  14. Compatibility of materials with the service and hazards from instability of contained fluids are not within the scope of this Code. See para. F323.

  15. Determining Code Requirements

  16. Code requirements for design and construction include fluid service requirements, which affect selection and application of materials, components, and joints. Fluid service requirements include prohibitions, limitations, and conditions, such as temperature limits or a requirement for safeguarding (see Appendix G). Code requirements for a piping system are the most restrictive of those that apply to any of its elements.

  17. For metallic piping not designated by the owner as Category M, High Pressure, or High Purity Fluid Service (see para. 300.2 and Appendix M), Code requirements are found in Chapters I through VI (the base Code) and fluid service requirements are found in

  • Chapter III for materials

  • Chapter II, Part 3, for components

  • Chapter II, Part 4, for joints

  1. For nonmetallic piping and piping lined with nonmetals, all requirements are found in Chapter VII. Paragraph designations begin with “A.”

  2. For piping in a fluid service designated as Category M, all requirements are found in Chapter VIII. Paragraph designations begin with “M.”

  3. For piping in a fluid service designated as Category D, piping elements restricted to Category D Fluid Service in Chapters I through VII, as well as elements suitable for other fluid services, may be used.

  4. For piping designated as High Pressure Fluid Service, all requirements are found in Chapter IX. These rules apply only when specified by the owner. Paragraph designations begin with “K.”

  5. For piping designated as High Purity Fluid Service, all requirements are found in Chapter X. Paragraph designations begin with “U.”

  6. Requirements for Normal Fluid Service in Chapters I through VI are applicable under severe cyclic conditions unless alternative requirements for severe cyclic conditions are stated.

  7. Requirements for Normal Fluid Service in Chapters I through VI are applicable for Elevated Temperature Fluid Service unless alternative requirements for Elevated Temperature Fluid Service are invoked.

  8. Appendices. Appendices of this Code contain Code requirements, supplementary guidance, or other information. See para. 300.4 for a description of the status of each Appendix.

  9. Code Cases. ASME issues Code Cases that are applicable to this Code. The Code Cases

  10. modify the requirements of this Code

  11. are applicable from the issue date until the Cases are annulled

  12. may be used only when approved by the owner. When so approved, the Code Cases shall be specified in the engineering design and become requirements of this Code.


Rules for the Process Piping Code Section B31.31 have been developed considering piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals.

  1. Content and Coverage

  2. This Code prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping.

  3. This Code applies to piping for all fluids, including

  4. raw, intermediate, and finished chemicals

  5. petroleum products

  6. gas, steam, air, and water

  7. fluidized solids

  8. refrigerants

  9. cryogenic fluids

  10. See Fig. 300.1.1 for a diagram illustrating the application of B31.3 piping at equipment. The joint connecting piping to equipment is within the scope of B31.3.

  11. Packaged Equipment Piping. Also included within the scope of this Code is piping that interconnects pieces or stages within a packaged equipment assembly.

  12. Exclusions. This Code excludes the following:

  13. piping systems designed for internal gage pressures at or above zero but less than 105 kPa (15 psi), provided the fluid handled is nonflammable, nontoxic, and not damaging to human tissues as defined in 300.2, and its design temperature is from −29°C (−20°F) through 186°C (366°F)

  14. power boilers in accordance with BPV Code2 Section I and boiler external piping that is required to conform to B31.1

  15. tubes, tube headers, crossovers, and manifolds of fired heaters that are internal to the heater enclosure

  16. pressure vessels, heat exchangers, pumps, compressors, and other fluid handling or processing equipment, including internal piping and connections for external piping


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