Hi everybody!
I would like to ask you a question that I hope you can answer me:

What is the scope of the ASME B31.1 and/or B31.3 Code, taking into account de piping diameter and/or the relationship diameter/thickness?

Thanks in advance.

Per B31.3-2004

300.1 Scope
Rules for the Process Piping Code Section B31.31 have
been developed considering piping typically found in
petroleum refineries; chemical, pharmaceutical, textile,
paper, semiconductor, and cryogenic plants; and related
processing plants and terminals.
300.1.1 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 Fig. 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.
300.1.2 Packaged Equipment Piping. Also included
within the scope of this Code is piping which interconnects
pieces or stages within a packaged equipment
assembly.
300.1.3 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 BPV Code2 Section
I and boiler external piping which is required to
conform to B31.1
(c) tubes, tube headers, crossovers, and manifolds of
fired heaters, which 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

May I understand that, for instance, a 48" pipe and a relationship between D/t very big (low thickness) is acceptable its calculation according to ASME B31.1.

Thank you so much for your quick response.

The scope does not have a cutoff based upon D/T ratios per se Appendix D states that the code SIFS for ratios over 100 are not applicable please take the time and effort to read the code rather than having me or somebody else feeding it to you one word at a time!!!!

But Caesar II is not applicable for pipe flexibility analysis for large D/t ratios. What is large? Well, as soon as buckling and local deformation become significant, that is when the force and moment distributions in the piping will be different from that predicted by pipe flexibility analysis. Caesar and other flexibility analysis programs assume a homogeneous cross-section. If you need stiffeners then you are probably outside the realm of pipe flexibility analysis and will need to turn to a different type of program such as ANSYS or FE/Pipe.

My understanding is that if we can compute the SIFs using FE Pipe or similar, then we can use CaesarII by overriding the SIFs.
Local stresses will then be addressed separately by using the forces/moments given by Caesar, at the points of support attachments.

As long as the piping is dominated by bending then you can use Caesar II for the analysis. And yes, you can override the SIFs that Caesar calculates and use your own that you get from FE/Pipe or similar.

Loren is absolutely positively correct technically but the code does not specifically and or explicitally say the same thing in such straight forward terms.