Repair of Div II Vessels

[Angsi]

Heard that mods and repair on Div II vessels are difficult and it needs to be brought back to the original fabricator.

Can someone please describe the requirements in general w.r.t to repair and mods to Div II vessels.

 

[metengr]

Repair and modifications to any pressure retaining item are based on your local Jurisdiction or regulatory body. In many cases, the National Board Inspection Code is typically cited. If this is the case, repairs and alterations are performed to this Code.

I will say that repairs are straight forward and would follow the requirements of the code of construction in terms of material and welding. For alterations, a design review is required by a competent authority (registered PE).
In either case, you are not forced to go back to the original fabricator.

 

[jte]

Angsi-

Glad to see you're considering post-construction issues up front - especially on an offshore installation where qualified repair organizations may be less available.

In addition to simply agreeing with what metengr stated, I'll add that many repair organizations will be leery of dealing with a Div 2 (not Div II by the way) vessel simply because they are not experienced with them. Naturally, there will be a restricted supply of fabricators for the original fabrication also.

One difference with a Div. 2 vessel compared to a Div. 1 is that the User's Design Spec. is site and service specific. You may take a Div. 1 drum designed for one service in Louisiana and move it to another service in California without going through a formal alteration process (but good engineering practice says that you should do some checking) provided you don't exceed the nameplate pressure and temperature. A Div. 2 vessel would require a formal alteration process for the same move: The location has changed and thus a PE must verify that the original design is still valid. Most likely the skirt's governing condition has changed from wind to seismic. The new calc's have to be formal, PE stamped, and verified by an AI.

I don't want to discourage you from using Div. 2 where it is appropriate... Just want to highlight some considerations in the decision you'll make. If you decide to go with Div. 2, please get someone who is familiar with Div. 2 to help you. Don't get into the situation I found myself in (as the owner's engineer) when the engineering consulting firm project engineer had a RFQ ready to go and asked me to review it: "Yeah, I have a user's design spec. I attached all of your company standards to the process data sheet." He literally had no clue what a Div. 2 User's Design Spec was, but was going out for quote for a multimillion dollar order. Sheesh.

jt