ASME BPVC 2023 Section VIII Div. 2

PART 4
DESIGN BY RULE REQUIREMENTS
4.1 GENERAL REQUIREMENTS
4.1.1 SCOPE
4.1.1.1 The basic requirements for application of the design-by-rules methods of this Division are described in 4.1.
The requirements of Part 4 provide design rules for commonly used pressure vessel shapes under pressure loading and,
within specified limits, rules or guidance for treatment of other loadings.
4.1.1.2 Part 4 does not provide rules to cover all loadings, geometries, and details. See Part 2 for User Responsibilities
and Users Design Specification.
4.1.1.2.1 Class 1. When design rules are not provided in Part 4 for a vessel or vessel part, the Manufacturer shall
either perform a stress analysis in accordance with Part 5 considering all of the loadings specified in the Users Design
Specification, or, with acceptance by the Authorized Inspector, use a recognized and accepted design-by-rule method
that meets the applicable design allowable stress criteria given in 4.1.6. If the design cannot be performed using Part
5 or a design-by-rule method e.g., creep-fatigue, a design method consistent with the overall design philosophy of Class
1 and acceptable to the Authorized Inspector shall be used.
4.1.1.2.2 Class 2. When design rules are not provided for a vessel or vessel part, the Manufacturer shall perform a
stress analysis in accordance with Part 5 considering all of the loadings specified in the Users Design Specification.
4.1.1.3 The design procedures in Part 4 may be used if the allowable stress at the design temperature is governed by
time-independent or time-dependent properties unless otherwise noted in a specific design procedure. When the vessel
is operating at a temperature where the allowable stress is governed by time dependent properties, the effects of joint
alignment see 6.1.6.1 and weld peaking see 6.1.6.3 in shells and heads shall be considered.
4.1.1.4 A screening criterion shall be applied to all vessel parts designed in accordance with this Division to determine
if a fatigue analysis is required. The fatigue screening criterion shall be performed in accordance with 5.5.2. If the
results of this screening indicate that a fatigue analysis is required, then the analysis shall be performed in accordance
with 5.5.2. If the allowable stress at the design temperature is governed by time-dependent properties, then a fatigue
screening analysis based on experience with comparable equipment shall be satisfied see 5.5.2.2.
4.1.1.5 See 4.1.1.5.1 and 4.1.1.5.2.
4.1.1.5.1 Class 1. Rules in Part 5 shall not be used in lieu of rules in Part 4.
4.1.1.5.2 Class 2. A design-by-analysis in accordance with Part 5 may be used to establish the design thickness
and/or configuration i.e., nozzle reinforcement configuration in lieu of the design-by-rules in Part 4 for any geometry
or loading conditions see 4.1.5.1. Components of the same pressure vessel may be designed thickness and configuration
using a combination of Part 4 designbyrules or any of the three methods of Part 5 designbyanalysis in 5.2.1.1.
Each component shall be evaluated for all of the applicable failure modes in 5.1.1.2 using the methodology of Part 4 or
Part 5. If the failure mode is not addressed in Part 4 e.g., ratcheting, then the analysis shall be in accordance with Part
5. Structural interactions between components shall be considered.
4.1.2 MINIMUM THICKNESS REQUIREMENTS
Except for the special provisions listed below, the minimum thickness permitted for shells and heads, after forming
and regardless of product form and material, shall be 1.6 mm 0.0625 in. exclusive of any corrosion allowance. Exceptions
are:
a This minimum thickness does not apply to heat transfer plates of plate-type heat exchangers.
b This minimum thickness does not apply to the inner pipe of double pipe heat exchangers nor to pipes and tubes
that are enclosed and protected by a shell, casing or ducting, where such pipes or tubes are DN 150 NPS 6 and less. This
exemption applies whether or not the outer pipe or shell is constructed to Code rules. All other pressure parts of these
heat exchangers that are constructed to Code rules must meet the 1.6 mm 0.0625 in. minimum thickness
requirements.
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4.1 4.1.2 ASME BPVC.VIII.2-2023