Answer: (1) External inspection. It refers to the regular online inspection of pressure vessels in use during operation, at least once a year. External inspection can be conducted by qualified pressure vessel inspectors of the inspection unit, or by professional pressure vessel personnel of the user unit approved by the safety supervision agency.
(2) Internal and external inspection (comprehensive inspection). It refers to the inspection of pressure vessels in use when they are shut down. Internal and external inspections should be conducted by qualified pressure vessel inspectors of the inspection unit. The inspection cycle is divided into:
1) For safety status levels 1 and 2, at least once every 6 years;
2) For safety status level 3, at least once every 3 years.
(3) Pressure test. It refers to the hydraulic test or air pressure test exceeding the maximum working pressure during the shutdown inspection of pressure vessels. For fixed pressure vessels, at least one pressure test should be conducted between every two internal and external inspections, and for mobile pressure vessels, at least one pressure test should be conducted every 6 years. The provisions on the contents of external inspection and internal and external inspection and safety grade shall be implemented in accordance with the "Inspection Procedures for In-use Pressure Vessels".
The first internal and external inspection cycle after commissioning is generally 3 years. The subsequent internal and external inspection cycles shall be determined by the inspection unit in consultation with the user unit based on the previous internal and external inspection results and reported to the local safety supervision agency for filing.
