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# ASME Section 8 Div 1 vs Div 27

## ASME Section 8 Div 1 vs Div 2

(OP)
Can someone familiar with both Div 1 and Div 2 design rules please give me a short explanation of the intent/use of each of these?  i.e., when to use Div 1 rules and when to use Div 2 rules?  I'm not a pressure vessel designer, but work with vessels, and I hear refences to each of these and want to be more informed.  Thanks.

### RE: ASME Section 8 Div 1 vs Div 2

2
If you make an advanced search on this site by using Div.2 as the keyword you'll get a lot of stuff to read on the subject.
In short: Div.1 provides simple design rules at the expense of a heavier vessel, Div.2 requires more detailed calculations, making the design cost more but allowing higher stresses, so that, for complex or large vessels, the overall cost will be lower. Both, as any standard, try to keep low the industrial costs for different classes of vessels, still maintaining an acceptable level of safety.

prex

http://www.xcalcs.com
Online tools for structural design

### RE: ASME Section 8 Div 1 vs Div 2

prex's interpretation is correct. Also, be advised that Sec. VIII Div.1 is intended for pressures below 3000 psi; beyond that ' deviations from and additions to the rules apply' meaning compliance with Div. 2 is required.

### RE: ASME Section 8 Div 1 vs Div 2

I think one of the most significant differences between Div 1 and Div 2 is Div 2 is used for cyrogenic vessels.

### RE: ASME Section 8 Div 1 vs Div 2

Div 2 considers the calculations under fatigue conditions.Div 1 does not

### RE: ASME Section 8 Div 1 vs Div 2

Guys-

Division 1 may be used for cryogenic vessels.

Division 1 considers fatigue. See the previous threads where this was discussed in detail.

jt

### RE: ASME Section 8 Div 1 vs Div 2

2
Regarding the comment made on use of VIII-2 for cryogenic vessels, please note that the toughness rules in VIII-1 & VIII-2 are identical. Further, VIII-1 contains rules in Part ULT which are specifically written for vessels in cryogenic service.

RE: Fatigue Design - This is a great misconception regarding VIII-1 & VIII-2. Paragraph UG-22 in VIII-1 lists all loads that must be considered in design, including cyclic service. Just because VIII-1 does not does not provide mandatory rules for fatigue design does not mean that this loading condition can be ignored. Where mandatory rules do not exist, then U-2(g) applies.

### RE: ASME Section 8 Div 1 vs Div 2

I think all of you are missing the most basic difference. The basic difference between section VIII Div 1 and Div 2, Div 3 is that Div 1 is a Code with design rules that are based on experience and Div 2 and 3 are based on design by
analysis.

In other words whe the Code was written it was well known that if you made a weld of a certian size it would give you satisfactory results. Also when Section VIII was origonaly written it had a safety factor of 5 it was lowered to 4 in the 1950's or 60's and was changed a few years ago to 3.5 and was given the term Design Margin.

### RE: ASME Section 8 Div 1 vs Div 2

Div. 2 are made for specific purpose, for specific location, and the vessel cannot be put into different service nor in different location without going through a recertification process.

I have spreadsheet for ASME Sect. VIII, both Div. 1 and Div. 2 Calculations.  Perhaps I can share.......

### RE: ASME Section 8 Div 1 vs Div 2

also, div 2 is for vessels 3,000 psi to 10,000 psi.
div 3 is for 10,000 psi and greater.

### RE: ASME Section 8 Div 1 vs Div 2

MarcoE-

Division 2 is by no means limited to vessels over 3000 psi. There are many, many vessels built to Div. 2 which have "ordinary" design pressures. I was heavily involved with one a few years ago which had a design pressure of 200 psi at 300°F. Just take a look a AG-100(a): "... The rules of this Division, taken as a whole, provide an alternative to the minimum construction requirements for the design, fabrication, inspection, and certification of pressure vessels falling within the scope of Division 1." It is an *alternative* to every vessel within the scope of Div. 1. Design pressure does not play a role in its applicability.

jt

### RE: ASME Section 8 Div 1 vs Div 2

Calculations for Div 2 vessel must be certified by Registered Professional Engineer.

Div 1 does not have this requirement.

### RE: ASME Section 8 Div 1 vs Div 2

Another difference between both divisions is the failure theory.
Div. 1 uses max principal stress menwhile div.2 uses max shear stress (Tresca).

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