AD 2000 Merkblatt vs ASME SEC VIII Div 2

[22448833]

hi,

My client have sphere which was design for VCM services and was design of AD Merblatt. Now they want to change the service to LPG. The local code refer to NFPA 58 which i believe says that the vessel should be designed and fabricated on ASME SEc VIII.

Thickness of sphere is 24 mm as per AD Merkblatt. If i use SEC VIII div 2 it comes out to be 24 mm but on SEC VIII div 1 it comes out to be 34 mm so we decide to use Div 2.

Now the local authority wants justification or comparison of AD Merkblatt with div 2. Can anypne please help me in this regard.

Thanks

Noman

 

[XL83NL]

If i use SEC VIII div 2 it comes out to be 24 mm but on SEC VIII div 1 it comes out to be 34 mm

Whats your reason for picking div 2 over div 1? Does the local jurisdiction allow this? Is this rerating of an existing vessel, or a new design & build? Rules for both cases may vary, depending on location and jurisdiction.

so we decide to use Div 2

Is the reason purely based on (what I assume is an) economical reason to reduce the thickness and thus associated cost? Where is this item to be installed? There's a lot of (useful) info missing, which may help you getting useful advice form the right people here (which Im not, just asking these questions since they matter).

Now the local authority wants justification or comparison of AD Merkblatt with div 2. Can anypne please help me in this regard.

It's apples and bananas, with the major difference probably being DBA (VIII-2) vs DBF (AD2000). The minor differences can be sorted out by yourself, but that shouldnt be too hard.

 

[TGS4]

XN83NL - VIII-2 is most certainly NOT a strictly Design By Analysis Code. There are plenty of vessels designed to VIII-2 that are strictly Design By Rules/Formulae.

Probably the most important aspect will be that the VIII-2 vessel will require a full-blown User's Design Specification, that will need to be certified by an Engineer (per the rules in VIII-2). That might end up being a substantial effort. But if you absolutely need the thickness to be 24mm, then do the work.

 

[XL83NL]

Youre correct TGS4, I forgot about that.

 

[22448833]

Guys actually this sphere was designed and installed in 1996 in Karachi. My client was using it for VCM now they will use it for LPG. Design code was AD Merkblatt and thickness is 24mm. Local regulation refer NFPA 58 which says LPG vessel should be design n ASME SEC VIII. I am using Div .2 so that we can give justification to the local authority.

Thanks

Noman

 

[TGS4]

This situation is beyond the level of assistance that you can expect to obtain for free over the internet. I highly recommend that you obtain the services of a specialist in the field.

However, my opinion is that back-dating a 2007+ Code to a vessel fabricated in 1996, without fully understanding the fabrication techniques, especially the NDE performed, is going to be a difficult mountain to climb.

 

[22448833]

thanks