Difference Between ASME Sec VIII Div. 1 and Div. 2

Both ASME Sec VIII Div 1 and Div 2 are used for pressure vessel design. Both divisions contain mandatory requirements, specific prohibitions, and non-mandatory guidance for pressure vessel materials, design, fabrication, examination, inspection, testing, certification, and pressure relief. So in a broad sense, both may seem to be similar but there are few distinct differences between both Divisions. In this article, we will explore the major differences between ASME Sec VIII Div 1 and Div 2.

Typical Pressure Vessel
Typical Column (Pressure Vessel) during erection stage

ASME Sec VIII Division 1 vs ASME Sec VIII Division 2

ParametersASME Sec VIII-Division 1ASME Sec VIII-Division 2
Design ApproachDivision 1 is focused on a design-by-rule approachDivision 2 on design-by-analysis approach
Design FactorDesign Factor used is 3.5 on tensile and other yield and
temperature considerations.
Design Factor of 3 (3.0 for Division 2, Class 1 and 2.4 for Division 2, Class 2) on tensile
and other
yield and temperature considerations.
Pressure LimitPressure typically up to 3000 psig.Pressure usually 600 psig and larger (less than 10000 psi).
Design RulesMembrane – Maximum stress
Generally Elastic analysis.
Very detailed design rules with Quality
(joint efficiency) Factors. Little stress
analysis required; pure membrane
without consideration of discontinuities
controlling stress concentration to a
safety factor of 3.5 or higher
Maximum Shear stress theory is the basis for Shell of Revolution.
Generally Elastic analysis
Membrane + Bending. Fairly detailed
design rules. In addition to the design
rules, discontinuities, fatigue and other
stress analysis considerations may be
required unless exempted and guidance
provided for in Appendix 4, 5 and 6
Design Calculations requires more detailed calculations than Division 1
Failure theory of DesignDivision 1 is based on normal stress theoryDivision 2 is based on maximum distortion energy (Von Mises criteria)
Experimental Stress
Analysis
Experimental methods of stress analysis are not required in normal case.Experimental stress analysis is introduced and may be required
Material and Impact
Testing
Few restrictions on materials; Impact
required unless exempted; UG-20, UCS 66/67 provides extensive
exemptions.
More restrictions on materials; impact
required in general with similar rules as
Division 1.
NDE RequirementsNDE requirements may be exempted
through increased design factor
More stringent NDE requirements;
extensive use of Radiographic Test, Ultrasonic Test, Magnetic Particle Test and Penetration Test.
Welding and
fabrication
Different types with butt welds and
others
Extensive use/requirement of butt welds
and full penetration welds including non-pressure attachment welds
Fatigue EvaluationNot mandatoryAD 160 for fatigue evaluation
ManufacturerManufacturer to declare compliance in
data report
Manufacturer’s Design Report certifying
design specification and code compliance
in addition to data report
Professional
Engineer
Certification
Normally not requiredProfessional Engineers’ Certification of
User’s Design Specification as well as
Manufacturer’s Design Report
Professional Engineer shall be experienced
in pressure vessel design
Code Stamp and
Marking
U Stamp with Addition markings
including W, B, P, RES; L, DF, UB, HT and  RT
U2 Stamp with Additional marking
including HT
Hydrostatic Test Pressure1.3 times design pressure1.25 times design pressure
Allowable Stress Value at a specified design temperatureLower, hence higher design marginHigher, hence lower design margin.
Shell thickness at same design pressureThickerThinner
Material CostHigherLower
Minimum Pressure Design Thickness Calculation Equationt=PD/2S – 1.2Pt=D/2{Exp(P/S)-1}
Hydrotest Stress CalculationIn Division 1, hydrotest stresses are not specifically limited and partial penetration nozzle welds are permitted.In Division 2, hydrotest stress calculations are mandatory as they are limited and full penetration nozzle welds are required
No of Vessels produced AnnuallyHigherLower
Reference Standards ASME B 1.13M AND ASME B 1.21M related to Screw threads are not listed Both standards are given as reference. 
Difference Between ASME Sec VIII Div. 1 and Div. 2
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Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

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