Near miss on a flange of a heat exchanger in a refinery

An operator noted a loose tube sheet flange stud on a high temperature, high pressure heat exchanger in an hydrodealkylation unit.
The stud was found to be cracked through. Analysis proved to be made of standard steel instead of the alloy type specified. Some of the other studs had started to crack.
The studs had been replaced on the previous shutdown when the heat exchanger was opened up to clean the tube bundle.

Incorrect component material

shell and tube heat exchanger

The failed studs had been replaced on the previous shutdown when the heat exchanger was opened up to clean the tube bundle.

DESCRIPTION OF THE CHEMICAL PROCESS
Hydrodealkylation is a chemical reaction that often involves reacting an aromatic hydrocarbon, such as toluene, in the presence of hydrogen gas to form a simpler aromatic hydrocarbon devoid of functional groups. An example is the conversion of 1,2,4-trimethylbenzene to xylene. This chemical process usually occurs at high temperature, at high pressure, or in the presence of a catalyst. These are predominantly transition metals, such as chromium or molybdenum. [Source: Wikipedia, accessed December 2022]

It is critical to have in place a Quality Control system for the consumables or parts replaced during maintenance or repair. Especially because these activities are often performed by contractors, there is always the possibility of a mismatch. The Quality Control could take the form of a check list to be executed by a plant supervisor, and/or consist in a full fledged quality control system agreed along the supply chain (for example based on ISO 9000 standard series).
It is critical to have in place a Quality Control system for the consumables or parts replaced during maintenance or repair. Especially because these activities are often performed by contractors, there is always the possibility of a mismatch. The Quality Control could take the form of a check list to be executed by a plant supervisor, and/or consist in a full-fledged quality control system agreed along the supply chain (for example based on ISO 9000 standard series).