scope:

Rules for the Process Piping Code Section B31.3¹ have been developed considering piping typically found in petroleum refineries; onshore and offshore petroleum and natural gas production facilities; chemical, pharmaceutical, textile, paper, ore processing, semiconductor, and cryogenic plants; food and beverage processing facilities; and related processing plants and terminals.

Content and Coverage

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

(b) This Code applies to piping for all fluids, including

(1) raw, intermediate, and finished chemicals

(2) petroleum products

(3) gas, steam, air, and water

(4) fluidized solids

(5) refrigerants

(6) cryogenic fluids

(c) See Figure 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.

Packaged Equipment Piping.

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

Exclusions.

This Code excludes the following: (a) 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)

(b) power boilers in accordance with ASME BPVC,² Section I and boiler external piping that is required to conform to ASME B31.1

(c) tubes, tube headers, crossovers, and manifolds of fired heaters that are internal to the heater enclosure

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

Units of Measure.

This Code states values in both SI and U.S. Customary units. Within the text, the U.S. Customary units are shown in parentheses or in separate tables. The values stated in each system are not exact equivalents; therefore, each system of units should be used independently of the other.

When separate equations are provided for SI and U.S. Customary units, those equations shall be executed using variables in the units associated with the specific equation. The results obtained from execution of these equations may be converted to other units.

When necessary to convert from one system of units to another, conversion should be made by rounding the values to the number of significant digits of implied precision in the starting value but not less than four significant digits for use in calculations.

Rounding.

The rules described in this paragraph apply unless otherwise specified in the Code or the engineering design. For purposes of determining conformance with specified limits in this Code, an observed value or a calculated value shall be rounded "to the nearest unit" in the last right-hand significant digit used in expressing the requirement, in accordance with the rounding method of ASTM E29, Using Significant Digits in Test Data to Determine Conformance with Specifications. ASTM E29 requires that when rounding a number to one having a specified number of significant digits, choose that which is nearest. If two choices are possible, as when the digits dropped are exactly a 5 or a 5 followed only by zeros, choose that ending in an even digit. See Appendix F, para. F300.1.5.

¹ B31 references here and elsewhere in this Code are to the ASME B31 Code for Pressure Piping and its various Sections, which are identified and briefly described in the Introduction.

² ASME BPVC references here and elsewhere in this Code are to the ASME Boiler and Pressure Vessel Code and its various Sections as follows:

Section I, Rules for Construction of Power Boilers

Section II, Materials, Parts C and D

Section III, Rules for Construction of Nuclear Facility Components, Division 1, Subsection NH

Section V, Nondestructive Examination

Section VIII, Rules for Construction of Pressure Vessels, Divisions 1, 2, and 3

Section IX, Welding, Brazing, and Fusing Qualifications