Shell and Head Replacement - Design Calculations?

[Tim37]

When a head and attached shell section of a Section VIII vessel is being replaced it would seem that new design calculations would not be necessary assuming the replacement is like-for-like to the original in all details, e.g., material, thickness, and location of nozzles. State is Illinois

Opinions please?

 

[Vinch]

Just some thoughts.
I would verify if this repair is required to be done according to original code of construction or current code.
If current code is use, design formulas may have changed from the original construction and that would require re-calculations.
In general, codes have evolved allowing for thinner material.I would not take that for granted but if that is the case it could give lower minimum wall thickness thus far increasing corrosion allowance and lifespan of the vessels.

 

[TJOrlowski]

If all variables are same (operating conditions, fluids, flowrates), and materials of replacement vessel and quality of workmanship are same, there should be no difference in life expectancy from a vessel built in 1950 or 2011.

Just because the theoretical formulas for thickness requirements and corrosion allowances have changed, the actual properties of fluids, and the phyiscal relationships between materials have not.

-TJ Orlowski

 

[boilerone]

If the original design and applicable code year are not changed then no new calculation is required. This is called 'repair' or 'replacement in-kind'.

 

[GenB]

NBIC repair but you mention location of nozzles? rthat is an alteration
so pls consult your AI...

 

[GenB]

NBIC repair but you mention location of nozzles? that is an alteration
so pls consult your AI...

 

[r6155]

Is the welding procedure equal to original construction?

Is the Original fabricator do the replacement?

Regards

r6155

 

[GenB]

I get it, if you use the same materials the design is the same, if other materials then it has to be recalculated and it would be better to the same Edition and Add. if available.