What are circumstances needed for re-inspection heat exchangers?

As we all know, we are professional for manufacturing heat exchangers and other pressure vessels. Many people may ask that when will be needed for re-inspection. 

Steel plates for the manufacture of heat exchangers are the first and second type, under what circumstances it will be needed for re-inspection.

One of the following circumstances should be re-inspection:

(1)Design drawings require re - inspection;

(2)The user requested re-inspection;

(3)The manufacturer can not determine the authenticity of the material or the manufacturer has doubts about the properties and chemical composition of the material;

(4)The certificate of quality of steel indicates that the copy is invalid or not equivalent.