why radiography take in welded joints?what are all the types and explain?

Answer 1

In weldments, porosity and surface defects, as well as actual cooling cracks, can be initiation sites for crack formation and propagation as a structure is loaded.

Radiography detects sub-surface flaws and can detect full penetration of welds hidden by underneath backing strips, for example.

This is a service that is offered by companies that have set themselves up in the vicinity of plants and operations where pressure vessel and structural welding is performed. Consult one of these companies with detailed questions.

Search in Yahoo search for "RT" and "Weld Examination".

Answer 2

To make sure you ( if your the welder ) do a good job. types? I guess your asking types of xray methods, most are done with radioactive isotopes, some very thin metals can be done with an xray machine, then there are CT machines designed to image metal objects for flaws. If you don't check the weld for weak spots you can end up blowing up a whole plant ( IE. the plant in Houston that blew up was caused by a faulty weld )