Formal training on the theory of each NDT method is required no matter what certification scheme you are eventually certified under.
This is where WorldSpec.org satisfies one major requirement for you. This foundational training MUST be taken at some point, usually, though not always first. It is essentially to fulfill the classroom, or written portion of the worldwide knowledge requirements and the body of knowledge each NDT tech needs to be successful in a career. Sometimes practical experience can occur prior to formal theory training. For example, sometimes the worker has been part of the NDT industry for years and not really knowledgeable of the theory behind the method he/she practices; as he/she has worked as a helper, etc. and is now being asked to get formal theory training and documented hours.
The amount of theoretical training hours vary between countries and certification programs. You should know what your certification path is and consult with a level III certified in the same certification scheme to get a good solid direction. The USA, Canada, and most other countries have specific requirements based on training and experience hours. All NDT methods have these requirements for both formal training hours and formal documented experience hours. WorldSpec uses ASNT CP-105 as the outline for all of our courses.
You will require more documented hours in most cases for both formal classroom hours and hands on, on-the- job training experience hours.
WorldSpec.org offers a quality option for NDT training that satisfies World-wide theory requirements to become fully certified, while saving you thousands of dollars in the process. All of your training must be approved and documented so consult your Level III expert.