ASME B31pressure Piping

Overview

Engineering reference data for ASME B31pressure Piping in standard organizations.

Key Formulas

ISO Standard

$ISO \; 9001:2015$

Quality management systems.

ASTM Standard

$ASTM \; E8$

Standard test methods for tension testing.

ANSI Standard

$ANSI/ASME \; B16.5$

Pipe flanges and flanged fittings.

Variables

References

• Original Source

B31 Code Edition Specifications

Pressure and Temperature Thresholds

B31.1 - Power Piping Requirements:

• Steam/vapor generation at pressures > 15 psig (100 kPa gage)
• High-temperature water at pressures > 160 psig (1103 kPa gage) and/or temperatures > 250°F (120°C)

B31.5 - Refrigeration Piping Temperature Range:

• Designed for temperatures as low as -320°F (-196°C)
• Maximum allowable pressure for exclusion: ≤15 psi (105 kPa) gage regardless of size

Code Status and Cross-References

Fluid Coverage by Code

B31.3 - Process Piping 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

Additionally includes piping interconnecting pieces or stages within packaged equipment assemblies.

B31.5 Exclusions

The following are not covered by B31.5:

• Self-contained or unit systems subject to Underwriters Laboratories or other nationally recognized testing laboratory requirements
• Water piping
• Piping designed for external or internal gage pressure not exceeding 15 psi (105 kPa) regardless of size
• Pressure vessels, compressors, or pumps (though connecting refrigerant and secondary coolant piping is included)

Detailed B31 Code Edition Specifications

This section provides expanded scope and application details for each B31 code edition.

B31.1 - Power Piping (2012)

Governs industrial and marine power piping systems. Its primary application includes:

• Boiler external piping for power boilers and high-temperature, high-pressure water boilers.
• Steam or vapor generated at pressures exceeding 15 psig (100 kPa gage).
• High-temperature water generated at pressures exceeding 160 psig (1103 kPa gage) and/or temperatures exceeding 250°F (120°C).

B31.2 - Fuel Gas Piping (Withdrawn 1968)

This code was withdrawn as a National Standard and replaced by *ANSI/NFPA Z223.1 (National Fuel Gas Code). It remains available from ASME as a reference for the design of gas piping systems from the meter to the appliance.

B31.3 - Process Piping (2012)

Covers piping in chemical, petroleum, and related processing plants. Its scope includes piping for all fluids:

• Raw, intermediate, and finished chemicals.
• Petroleum products.
• Gas, steam, air, and water.
• Fluidized solids.
• Refrigerants.
• Cryogenic fluids. It also applies to piping interconnecting stages within packaged equipment assemblies.

B31.4 - Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids (2012)

Prescribes requirements for liquid transportation pipelines. The scope explicitly includes:

• Primary and auxiliary piping at terminals, tank farms, pump stations, and metering stations.
• Storage tanks and interconnecting piping.
• Liquid piping on dedicated property within refineries, processing plants, and bulk plants.
• Aspects of operation and maintenance related to safety and public protection.

The scope also covers transport of specific liquids such as crude oil, condensate, LPG, carbon dioxide, liquid alcohol, and anhydrous ammonia.

B31.5 - Refrigeration Piping and Heat Transfer Components (2013)

Applies to refrigerant, heat transfer, and secondary coolant piping for service temperatures as low as -320°F (-196°C).

This code shall not apply to:

• Self-contained unit systems subject to UL or similar lab requirements.
• Water piping.
• Piping designed for pressure not exceeding 15 psi (105 kPa) regardless of size.
• Pressure vessels, compressors, or pumps themselves (but does include their connecting refrigerant piping).

B31 Code Scopes and Exclusions

The ASME B31 codes define specific boundaries for their application. Understanding these scopes is critical for compliance.

Scope of B31.4

This code governs piping systems transporting specific liquids between key industrial facilities. Its scope includes:

• Piping between producers' lease facilities, tank farms, natural gas processing plants, refineries, stations, ammonia plants, and terminals.
• Primary and associated auxiliary liquid petroleum and liquid anhydrous ammonia piping at pipeline terminals (marine, rail, and truck), tank farms, pump stations, pressure reducing stations, and metering stations.
• Storage and working tanks, including pipe-type storage, and interconnecting piping.
• Liquid piping located on designated property within petroleum refineries, gas processing plants, and bulk plants.

Exclusions from B31.5

B31.5 does not apply to the following systems and components:

• Self-contained or unit systems subject to the requirements of Underwriters Laboratories or other nationally recognized testing laboratories.
• Water piping.
• Piping designed for a pressure not exceeding 15 psi (105 kPa) regardless of size.
• Pressure vessels, compressors, or pumps, although all connecting refrigerant and secondary coolant piping is included.

Key Definitions

• Pressure Piping: A piping system that carries fluids (liquids, gases, or mixtures) under internal or external pressure. The ASME B31 codes provide the governing rules for the design, materials, fabrication, and testing of these systems.
• Code: A set of recognized and generally accepted engineering standards and practices that establish minimum requirements to ensure safety and reliability.

Key Applications

This table summarizes the primary industrial applications for the main B31 code sections discussed.

B31 Code Scopes Summary Table

Refrigerant Temperature Limit

For refrigeration piping systems under *B31.5, the design must account for fluid temperatures as low as:

$T_{min} = -320^\circ F \ (-196^\circ C)$

This defines the lower bound for material selection and testing requirements for components carrying refrigerants or secondary coolants in this service.