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 the erection stage

ASME Sec VIII Division 1 vs ASME Sec VIII Division 2

ParametersASME Sec VIII-Division 1ASME Sec VIII-Division 2
Design ApproachASME Sec VIII Division 1 is focused on a design-by-rule approachASME Sec VIII Division 2 on the other hand, is based on a design-by-analysis approach
Design FactorThe design Factor used is 3.5 on tensile and other yields 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 is 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 DesignASEM Sec VIII Division 1 is based on the normal stress theoryASME Sec VIII Division 2 is based on maximum distortion energy (Von Mises criteria)
Experimental Stress
Analysis
Experimental methods of stress analysis are not required in normal cases.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 factorMore stringent NDE requirements;
extensive use of Radiographic tests, Ultrasonic Tests, Magnetic Particle Tests, and Penetration Tests.
Welding and
fabrication
Different types with butt welds and othersExtensive use/requirement of butt welds
and full penetration welds including non-pressure attachment welds
Fatigue EvaluationNot mandatoryAD 160 for fatigue evaluation
ManufacturerManufacturers are to declare compliance with the data reportManufacturer’s Design Report certifying
design specification and code compliance in addition to a data report
Professional
Engineer
Certification
Normally not requiredProfessional Engineers’ Certification of
User’s Design Specifications as well as
Manufacturer’s Design Report
Professional Engineers 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 the same design pressureThickerThinner
Material CostHigherLower
Minimum Pressure Design Thickness Calculation Equationt=PD/2S – 1.2Pt=D/2{Exp(P/S)-1}
Hydrotest Stress CalculationIn ASME Sec VIII Division 1, hydro test stresses are not specifically limited and partial penetration nozzle welds are permitted.In the ASME Sec VIII Division 2, hydro test stress calculations are mandatory as they are limited and full penetration nozzle welds are required
No of Vessels produced AnnuallyLargerLower
Reference Standards ASME B 1.13M AND ASME B 1.21M related to Screw threads are not listed Both standards are given as references. 
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.

13 thoughts on “Difference Between ASME Sec VIII Div. 1 and Div. 2

  1. I am a Rotating Equipment Engineer, who finds this page useful and concise on the subject topic. Thank you so much for sharing.

  2. Anup – great job on the summary comparison. I work in an Oil & Gas major and my background is in rotating equipment engineering and now also Quality Management. This is a very useful summary of Div 1 vs Div 2.
    Sam

  3. Hi Anup Kumar Dey ,

    really appreciate your valuable information , defiantly benefited from it
    do you have any any smiler comparison Difference Between ASME Sec VIII Div. 2 and ASME V Div PD/5500

    have good day

  4. CAN YOU PLEASE MAKE A COMPARISON TABLE BETWEEN ASME SECTION VIII DIV 1 AND EN 13458 – 2 FOR THE DESIGN OF CRYOGENIC PRESSURE VESSELS.

  5. Hi,
    thank you for your website.

    I would like to comment that Division 2 comprises both Design by Rule and Design by Analysis requirements, not only DbA.

    It is not fair to oppose both codes based on DbR vs DbA 😉

    Part 4 Design by Rule Requirements (approximately 400 pages out of 870)
    Part 5 Design by Analysis Requirements (approximately 30 pages out of 870)

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