ASME Section VIII, Div 1, Div 2 or Div 3

[engpes]

We are designing a high pressure vessel (10,000 psi design pressure), and are trying to determine which ASME section VIII division to design it to (1, 2, or 3). Division 3 in the opening remarks says that it should be used for vessels exceeding 10,000 psi, but does states that it does not intend to specify max or min pressure limits for its use. This will be a carbon steel welded vessel.

My questions are as follows:

1.) Is it solely up to the designer to specify whether division 3 can be applied? Are there any guidelines in writing?

2.) My interpretation of the "basic" differences between divisions 1, 2, and 3 are that 1 is a design by rules guide (most conservative), 2 is a mixture of rules and analysis (less conservative), and 3 is a pure analysis method based on higher allowable stresses and higher strength materials (least conservative)? Are there any recommendations that spell out which division should be used for which application?

I interpret this to be up to the design engineer, but was curious to get others' take on this. Thank you in advance for you assistance.

 

[SnTMan]

engpes, the jurisdiction may have a say, as may the owner. Either of those apply?

What kind of vessel is it? A small lab vessel? A large reactor? Might make a difference.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[jte]

Well, this query will get a lot of responses! To answer your specific questions succinctly:

1) Yes, up to the designer (more precisely, an agreement between the designer and owner/user and possibly jurisdiction), and no, there are not hard-wired guidelines published by ASME.

2) Your interpretation is more or less correct. Strictly speaking, one can use Div. 2 exclusively as a design by rule code, and you can also use it exclusively as a design by analysis code. Either way, the rules of the other Parts besides 4 and 5 will apply.

Very generally speaking, from my experience you'll see Div. 1 vessels from atmospheric to around 5000 psi. You'll see Div. 2 vessels from around 500 psi to 15,000 psi. I've not worked with Div. 3, but I'd expect a similar overlap, say 6000 psi to 30,000 psi.

Before everybody piles on, focus on the phrases "very generally speaking", and "from my experience". Your experience will vary, I get that.

For what its worth, I'm currently involved with a design for a VIII Div. 1 vessel. At well over 10,000 psi. If it were solely my decision I'd probably push for Div. 2, but it isn't. That's fine, the others involved have their valid reasons for preferring Div. 1, but there is a bit of extra effort involved in demonstrating Div. 1 compliance.

Depending on your particular application and owner/user, I'd be surprised to see you go Div. 1. If it were for my company, I'd push you towards Div. 2, but I recognize that in other industries and other companies they may see an advantage to Div. 3.

 

[SnTMan]

As always, the answer is "Well, it depends...."

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[TGS4]

jte's reply is the most nuanced that you will likely get.

In my mind, the choice of Div 2 or 3 also depends on whether or not the vessel is in cyclic service.

Repair and maintenance, as well as record-keeping of the in-service vessel may have some bearing on your decision.

 

[pradipgoswami]

From my experience I would say, DIV-3 is relatively new concept in ASME codes.One needs fabricators, Steel Mills..... who're conversant with the product requirements of DIV-3 codes.

DIV-2 had been there for many years, fabricators, steel mills , welding consumable manufacturers... and others are quite familiar with this code. It may be a good idea to seek the opinions of the shortlisted fabricators and accordingly choose the best fabrication friendly design code(DIV-2 or DIV-3).

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means.

 

[r6155]

Insurance rate cost should be considered by the user between Div 1, 2 and 3 before design

Regards
r6155

 

[MrPDes]

If you have a vessel where a bit of extra thickness is not an issue and fatigue loading or unique stress producing geometry etc is not a problem then Div 1 is adequate for any pressure.

Even if there is fatigue or the geometry of your vessel is not suitable for Div 1 "design by rules", you can still use U-2(g) and design the entire vessel to Div 2, Div 3 or in theory other codes like PD 5500. However you need to continue using the material design margins of Div 1, hence the extra thickness.

Edit: as per Div 1 U-1(d) and similar text in equivalent sections of Div 2 and Div 3.

The rules of this Division have been formulated on the basis of design principles and construction practices applicable to vessels designed for pressures not exceeding 3,000 psi (20 MPa). For pressures above 3,000 psi (20 MPa), deviations from and additions to these rules usually are necessary to meet the requirements of design principles and construction practices for these higher pressures. Only in the event that after having applied these additional design principles and construction practices the vessel still complies with all of the requirements of this Division may it be stamped with the applicable Certification Mark with the Designator.