What types of damage have been observed during the maintenance of bolted flange joints?
It is common for the nut to generate a more or less deep pit on the flange surface due to friction during the tightening process. In such cases, the linear relationship between tightening torque and tension on the rod is compromised.
This phenomenon is more pronounced on smaller-sized bolts.
As bolt size increases, the phenomenon is less frequent, but the use of appropriate washers is still a highly effective precaution.