This is what happens to a flange when you use a grinder to remove the bolts. The story goes as this; a diver used an Impact (A hydraulic Impact Wrench for you non-offshore type people) to remove the bolts from this three Inch Flange. Instead of gently using the Impact until the socket gripped the bolts, he went full force at them. Every nut on the bolts became rounded off until the Impact was useless. The diver then asked for the grinder and went to town through the middle of the flange. As you can see o-ring face is completely gone. The flange in the picture was the side we were going to reattach to. We had to remove that side also and weld a new flange piece. This was one (and only recorded) museum pieces of bad diving mistakes. Sadly it was lost to scrap iron bin by a company man who thought a clean deck meant all his mistakes would by looked over by his relief.