Problems like these are not uncommon in the field, and they often go unnoticed. This is a case of an unauthorized surgery on a prismatic section — likely by a contractor, amputating the bottom flange, sinking some teeth in to the web even, to make way for pipework and its flange assembly. It’s like hacking a few toes in order to force-fit a new shoe. Introducing needless stress discontinuities in load carrying structural elements like these drive engineers up the wall.
I modelled the beam with a crude section of the cut-out at an approximate location identified, and performed an analysis to determine at what global load it would begin yielding. (The tool uses Green strain deformation mechanics.)
Steel is forgiving. The beam in question fortunately isn’t safety critical, and it turns out that it is capable of nearly twice the load it was designed to carry in its elasto-plastic capacity. (Plastic hinge forms at about four times the initial applied global load in the cut section.)