**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.

## ASME Sec VIII Division 1 vs ASME Sec VIII Division 2

ASME Section VIII, Division 1 is a straightforward design-by-rule method used by engineers to design pressure vessels based on rules. It’s conservative and usually leads to a sturdier design.

ASME Section VIII, Division 2 requires more detailed calculations and allows vessels to handle higher stresses, making it suitable for vessels with specific purposes and fixed locations.

The key difference between Division 1 and Division 2 is in how they handle stress. Division 1 uses normal stress theory, while Division 2 uses maximum distortion energy theory (Von Mises). The major differences between the two divisions of ASME BPVC Sec VIII Div 1 and Div 2 are tabulated below:

Parameters | ASME Sec VIII-Division 1 | ASME Sec VIII-Division 2 |

Design Approach | ASME Sec VIII Division 1 is focused on a design-by-rule approach | ASME Sec VIII Division 2 on the other hand, is based on a design-by-analysis approach |

Design Factor | The 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 Limit | Pressure typically up to 3000 psig. ASME Sec VIII Div 1 is more suitable for low-pressure applications. | Pressure is usually 600 psig and larger (less than 10000 psi). ASME Sec VIII Div. 2 caters to high-pressure applications. |

Design Rules | Membrane – 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 | Simple Calculations. | requires more detailed calculations than Division 1 |

Failure Theory of Design | ASEM Sec VIII Division 1 is based on the normal stress theory | ASME Sec VIII Division 2 is based on maximum distortion energy (Von Mises criteria) |

Experimental StressAnalysis | Experimental methods of stress analysis are not required in normal cases. | Experimental stress analysis is introduced and may be required |

Material and ImpactTesting | 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 Requirements | In ASME Sec VIII Div. 1, the NDE requirements may be exempted through increased design factors. | Div. 2 has more stringent NDE requirements; extensive use of Radiographic tests, Ultrasonic Tests, Magnetic Particle Tests, and Penetration Tests. |

Welding andfabrication | Different types with butt welds and others. | Extensive use/requirement of butt welds and full penetration welds including non-pressure attachment welds. |

Fatigue Evaluation | Not mandatory. | AD 160 for fatigue evaluation |

Manufacturer | Manufacturers are to declare compliance with the data report. | Manufacturer’s Design Report certifying design specification and code compliance in addition to a data report. |

ProfessionalEngineer Certification | Normally not required. | Professional 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 andMarking | 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 Pressure | 1.3 times design pressure. | 1.25 times design pressure. |

Allowable Stress Value at a specified design temperature | Lower, hence higher design margin. | Higher, hence lower design margin. |

Shell thickness at the same design pressure | Thicker | Thinner. |

Material Cost | Higher. | Lower. |

Minimum Pressure Design Thickness Calculation Equation | t=PD/2S – 1.2P | t=D/2{Exp(P/S)-1} |

Hydrotest Stress Calculation | In 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 Annually | Larger | Lower |

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

Good work!

Good job

Thank you very much and Good Job, its very easy to understand the difference.

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

Very useful, concise comparison.

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

great work. it is very useful.

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

Good work, very appropriate to my work. Thanks

Nice and very informative comparison

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

Good Job Anup.

Thank you for share it.

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)