Standard: ASME B31.1


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Rules for this Code Section have been developed considering the needs for applications that include piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems.

This Code prescribes requirements for the design, materials, fabrication, erection, test, inspection, operation, and maintenance of piping systems.

Piping as used in this Code includes pipe, flanges, bolting, gaskets, valves, pressure-relieving valves/ devices, fittings, and the pressure-containing portions of other piping components, whether manufactured in accordance with Standards listed in Table 126.1 or specially designed. It also includes hangers and supports and other equipment items necessary to prevent overstressing the pressure-containing components.

Rules governing piping for miscellaneous appurtenances, such as water columns, remote water level indicators, pressure gages, gage glasses, etc., are included within the scope of this Code, but the requirements for boiler appurtenances shall be in accordance with Section I of the ASME Boiler and Pressure Vessel Code, PG-60.

The users of this Code are advised that in some areas legislation may establish governmental jurisdiction over the subject matter covered by this Code. However, any such legal requirement shall not relieve the owner of his inspection responsibilities specified in para. 136.1.

Power piping systems as covered by this Code apply to all piping and their component parts except as excluded in para. 100.1.3. They include but are not limited to steam, water, oil, gas, and air services.

(A) This Code covers boiler external piping as defined below for power boilers and high-temperature, highpressure water boilers in which steam or vapor is generated at a pressure of more than 15 psig [100 kPa (gage)]; and high temperature water is generated at pressures exceeding 160 psig [1 103 kPa (gage)] and/or temperatures exceeding 250°F (120°C).

Boiler external piping shall be considered as piping that begins where the boiler proper terminates at

(1) the first circumferential joint for welding end connections; or

(2) the face of the first flange in bolted flanged connections; or

(3) the first threaded joint in that type of connection; and that extends up to and including the valve or valves required by para. 122.1.

The terminal points themselves are considered part of the boiler external piping. The terminal points and piping external to power boilers are illustrated by Figs. 100.1.2(A.1), 100.1.2(A.2), 100.1.2(B.1), 100.1.2(B.2), 100.1.2(B.3), and 100.1.2(C).

Piping between the terminal points and the valve or valves required by para. 122.1 shall be provided with Data Reports, inspection, and stamping as required by Section I of the ASME Boiler and Pressure Vessel Code. All welding and brazing of this piping shall be performed by manufacturers or contractors authorized to use the ASME Certification Mark and appropriate Designators shown in Figs. PG-105.1 through PG-109 of Section I of the ASME Boiler and Pressure Vessel Code. The installation of boiler external piping by mechanical meansmay be performed by an organization not holding an ASME Certification Mark. However, the holder of a valid ASME Certification Mark, Certificate of Authorization, with an “S,” “A,” or “PP” Designator shall be responsible for the documentation and hydrostatic test, regardless of the method of assembly. The quality control system requirements of Section I of the ASME Boiler and Pressure Vessel Code shall apply. These requirements are shown in Mandatory Appendix J of this Code.

The valve or valves required by para. 122.1 are part of the boiler external piping, but do not require ASME Boiler and Pressure Vessel Code, Section I inspection and stamping except for safety, safety relief, and relief valves; see para. 107.8.2. Refer to PG-11.

Pipe connections meeting all other requirements of this Code but not exceeding NPS 1⁄2 (DN 15) may be welded to pipe or boiler headers without inspection and stamping required by Section I of the ASME Boiler and Pressure Vessel Code.

(B) Nonboiler external piping includes all the piping covered by this Code except for that portion defined above as boiler external piping.

This Code does not apply to the following: (A) economizers, heaters, pressure vessels, and components covered by Sections of the ASME Boiler and Pressure Vessel Code.

(B) building heating and distribution steam and condensate piping designed for 15 psig [100 kPa (gage)] or 6 less, or hot water heating systems designed for 30 psig [200 kPa (gage)] or less.

(C) piping for hydraulic or pneumatic tools and their components downstream of the first block or stop valve off the system distribution header.

(D) piping for marine or other installations under Federal control.

(E) towers, building frames, tanks, mechanical equipment, instruments, and foundations.

(F) piping included as part of a shop-assembled packaged equipment assembly within a B31.1 Code piping installation when such equipment piping is constructed to another B31 Code Section (e.g., B31.3 or B31.9) with the owner’s approval. See para. 100.2 for a definition of packaged equipment.


NASA Lessons:
  • This lesson addresses a catastrophic failure of a high pressure (225 psig) steam line strainer largely due to inappropriate use of material and the violation of the maximum allowance stress for the cast iron strainer per ASME B31.1. This lesson is relevant to paragraphs 122.3.1, 122.7.4, and 124.6 of this ASME Prssure Piping code
Organization: ASME International
Document Number: asme b31.1
Publish Date: 2016-06-30
Page Count: 366
Available Languages: EN
DOD Adopted: NO
ANSI Approved: YES
Most Recent Revision: YES
Current Version: YES
Status: Active

Document History

Document # Change Type Update Date Revision Status
ASME B31.1 Change Type: STCH Update Date: 2014-08-15 Revision: 14 Status: INAC
ASME B31.1 Change Type: STCH Update Date: 2012-06-29 Revision: 12 Status: INAC
ASME B31.1 Change Type: STCH Update Date: 2010-12-31 Revision: 10 Status: INAC
ASME B31.1 Change Type: ADB Revision: 07 Status: INAC
ASME B31.1 Change Type: ADB Update Date: 2009-08-07 Revision: 07 Status: INAC
ASME B31.1 Change Type: ADA Update Date: 2008-06-09 Revision: 07 Status: INAC
ASME B31.1 Change Type: Update Date: 2007-12-07 Revision: 07 Status: INAC
ASME B31.1 Change Type: ADB Revision: 04 Status: INAC
ASME B31.1 Change Type: ADB Update Date: 2006-12-15 Revision: 04 Status: INAC
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