Let's put our horse sense to work.
When the vessel was originally signed off (how I like those King's English expressions!) it was supposed to be OK.
Then, before installing the refractories, the contractor ground a groove which happened to be too deep and it had to be repaired by welding. Who warrants me that the new welding will stand the vessel operating pressure? If I were the client, or the inspector, I'd require a new hydro test.
But then, numerous cracks were discovered, not only in the rewelded area but also in the original metal, which demonstrates that whoever signed the vessel off was, to say the least, negligent or ignorant. Now you are repairing the cracks by welding.
Are you sure you've identified all of the existing cracks? Who warrants me that cracks are not spread all over the vessel?
If I were the client, or the inspector, apart form the hydro test I'd also require also a complete search of cracks all over the vessel weldings.
Giovanni S. Crisi
Sao Paulo - Brazil