ASME B31.3
Definition
Process Piping Code — prescribes requirements for materials, design, fabrication, assembly, erection, examination, inspection, and testing of piping systems for process plants, including refineries, chemical plants, pharmaceutical operations, and related processing installations. It covers pipe, fittings, flanges, bolting, gaskets, valves, and pressure-relieving devices.
Context
The governing code for process piping design and construction. Inspectors reference ASME B31.3 for minimum wall thickness calculations, allowable stresses, and material limitations. It defines the original design basis against which in-service conditions are compared.
Examples
- A piping engineer calculates the minimum required wall thickness per ASME B31.3 for a new 8-inch carbon steel line operating at 400F and 300 psig.
- An integrity assessment compares the measured wall thickness to the ASME B31.3 minimum required thickness to determine remaining corrosion allowance.
Applicable Standards
- ASME B31.3
- ASME BPVC Section II
Related Terms
Piping Inspection Code — provides requirements for the inspection, repair, alteration, and rerating of in-service metallic and fiberglass-reinforced plastic piping systems. It covers inspection practices for maintaining the mechanical integrity of process piping, including determination of corrosion rates, remaining life, and inspection intervals.
Minimum Required Thickness(t_min)The minimum wall thickness required by the applicable design code to safely contain the operating pressure at the design temperature, considering the allowable stress of the material, weld joint efficiency, and applicable code margins. This is the absolute minimum thickness for pressure containment — below this value, the equipment exceeds its design basis and must be retired, repaired, or de-rated.
Nominal ThicknessThe wall thickness specified at the time of design and fabrication, before any in-service degradation. Nominal thickness is the starting point for remaining life calculations and is the thickness that should be measured at a CML immediately after construction. It includes the minimum required thickness plus the corrosion allowance plus any manufacturing tolerance.
Design ConditionsThe maximum temperature, pressure, and other parameters for which equipment is designed and rated. Design conditions define the mechanical design basis and determine the minimum required wall thickness, material selection, and construction code requirements. Actual operating conditions should remain within the design envelope — operation outside design conditions requires engineering assessment and potentially re-rating or modification.
Where this appears in Reliatic
This concept is used in the Reports module.