There are 10 ways to transilluminate the welding seam of air separation unit, which are suitable for different occasions. Single wall is the most commonly used transilluminating method, but when the radiation source or film cannot enter the inside small diameter vessel and pipeline, double wall transilluminating method is adopted. The selection of transillumination method should consider all factors synthetically. For example, according to the principle of selecting the transillumination method which is beneficial and improves the sensitivity, single wall transillumination should be selected as far as possible. According to the principle which is conducive to the detection of corresponding defects, the outside radiation source is preferred for the detection of cracks on the inner wall of the container.
