Answer: External inspection is mainly macroscopic inspection, and non-destructive testing and other methods are used only when necessary. Macroscopic inspection is a method of inspection based on vision, hearing and touch. It usually includes visual inspection (including magnifying glass, reflector, etc.), hammer inspection, lighting inspection, sample inspection, measuring tool inspection, etc. External inspection can be carried out by the user unit or the inspection unit, and the external inspection report is kept by the user unit. It is a relatively simple and practical inspection method. It can not only directly detect surface defects on pressure vessels, so that we have a general understanding of the actual condition of pressure vessels, but also provide important clues and basis for further detailed inspection of what inspection methods should be used.
