ASME B31. 1 or Power Piping Code provides rules for piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems

Power Piping code ASME B31. 1 uses a maximum SIF of 2.0 for reducers while stress calculation. ASME B31. 3 uses a factor of safety of 3

ASME B31. 3 contains requirements for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals

ASME B31. 3 is a Code for the design and erection of chemical plant and oil refinery piping.

ASME B31.1 is Process piping Code

ASME B31.1 clearly specifies the allowable sagging value as 2.5 mm

As per ASME B31.3, the basic allowable material stress value is higher than the ones in ASME B31.3

ASME B31.3 code does not specifically say about any limit of allowable sagging

ASME B31.3 uses a factor of safety relatively lower than ASME B 31.1

B31.3 uses a SIF of 1.0 for butt welded joints

ASME B31.3 uses a simplified single SIF Approach

The allowable value of occasional stress as per ASME B31.3

The equation for pipe wall thickness calculation in B31.1 is valid for t<D/6.

B31.1 instructs to use a pneumatic test pressure in between (1.2 to 1.5) times the design pressure for the piping system.

While Sustained and Occasional stress calculation, the Process Piping code ASME B31.1 reduces the thickness by corrosion and other allowances

The power piping code, B31.3 does not provide any such rules for pipe materials below -29 deg C

Process Piping following ASME B31.3 is normally designed for 20 to 30 years of service life.

ASME B31.3 provides specific equations for PSV reaction force calculation.

The hydrostatic test pressure following ASME B31.1 is 1.5 times the piping design pressure.

The welder and brazer qualifications are not identical in ASME 31.1 & ASME 31.3