Please, anyone can explain what are to be followed while inspect the plate. For example in Plate 12mm thk x 2500 x 12000 how many places thk, width and length to be taken.
It depends on what your needs are. You may only want to measure thickness at the ends - center point and both edges and visually examine surfacees for scabs and other surface flaws. You may want to UT check for laminarrion. If mechanical properties are suspect you may need to perform tensile and impact testing.
Here in the west, we produce finished goods in accordance with agreed upon codes and standards.
US Codes and standards are used around the world, but other standards exist. Within those codes and standards are the inspection requirements for the finished good. ASTM and ASME material, dimensional and inspection standards are commonly used in commerce
These codes and standards are usually referenced in the plate purchase order..... It is what the customer wants !!!! .... Requirements for a steel plate to be used in a nuclear power plant are different than those for a common Structural Steel baseplate
Aside from your anxiety you have really told us nothing..
I'll throw in the EN/ISO codes, with similar tests to be performed as in the ASTM standards, but according to EN/ISO standards/work methods, using EN/ISO based training and accreditation.
Et voilà, I've just doubled the playing field.