ASME B31.1 vs. ASME B31.3 | What’s the difference?

The simplest way to understand the differences between ASMNE B31.1 and B31.3 is their application:

“What type of facility is the piping intended to serve?” The answer …

• • ASME B31.1 is primarily the code for power-generation and utility piping.
  • ASME B31.3 is primarily the code for process-plant piping.

Here is a practical industry breakdown.

ASME B31.1 — Power Piping

ASME B31.1, Power Piping is one of the most widely recognized piping codes used in the power-generation industry. Developed by the American Society of Mechanical Engineers (ASME), B31.1 establishes requirements for the design, materials, fabrication, assembly, erection, examination, inspection, testing, and operation of power piping systems. It applies primarily to piping found in electric power stations and industrial facilities where piping transports steam, water, air, gas, and other fluids associated with power production.

The code is particularly important for systems operating at elevated temperatures and pressures, where the integrity of piping, welds, supports, valves, and other components is critical to plant safety and reliability.

To make this clearer, let’s look at the types of facilities that required B31.1 piping:

Typical B31.1 pipe systems

For a combined-cycle plant, for example:

• Main steam
• Hot reheat
• Cold reheat
• Boiler feedwater
• Condensate
• Auxiliary steam
• Blowdown
• Boiler piping
• Steam turbine piping
• Feedwater systems
• Certain cooling/utility systems

ASME B31.3 — Process Piping

ASME B31.3, Process Piping is one of the principal piping codes used throughout the chemical, petrochemical, refining, pharmaceutical, and other process industries. Published by the American Society of Mechanical Engineers (ASME), B31.3 establishes requirements for the design, materials, fabrication, assembly, erection, examination, inspection, and testing of process piping systems.

It covers piping that transports liquids, gases, and other fluids within processing facilities, including systems that may operate at high pressures, elevated or cryogenic temperatures, or involve hazardous, toxic, flammable, or corrosive substances. The code provides engineers and fabricators with a consistent framework for designing and constructing piping systems that can safely withstand their intended operating conditions.

The types of facilities that require B31.3:

Typical ASME B31.3 Process Piping Systems include:

• Process-fluid piping
• Hydrocarbon piping
• Chemical piping
• Hydrogen piping
• Nitrogen piping
• Fuel and utility piping
• Steam and condensate piping
• Cooling-water and chilled-water piping
• Flare piping
• Instrument-air piping
• Fire-protection piping

In summary, the importance of these codes extends well beyond simply meeting a specification. Proper application of B31.1 and B31.3 helps protect people, equipment, production, and the environment by reducing the likelihood of piping failures, leaks, ruptures, and other potentially catastrophic events.

For pipe-fabrication shops and EPC contractors, compliance provides a common technical language between the designer, fabricator, inspector, and plant owner. Ultimately, B31.1 and B31.3 provide the foundation for building piping systems that are not only structurally sound and reliable, but also capable of performing safely over many years of demanding industrial service.