External Inspection of Pressure Vessels
Also known as in-service inspection, the main contents of the inspection are:
- Whether there are abnormal phenomena such as cracks, deformation, leakage, local overheating, etc. on the outer surface of the pressure vessel;
- Whether the safety accessories are complete, sensitive, and reliable; whether the fastening bolts are intact and all tightened;
- Whether the foundation has subsidence, inclination, and whether the anti-corrosion layer is damaged or not.
External inspection is not only the work of the inspector but also the routine inspection item of the operator. If any phenomenon endangering safety is found (such as cracks, deformation, serious leakage of pressure components, etc.), the operation should be stopped and the relevant personnel should be reported in time.
Internal and external inspection
Internal and external inspection of pressure vessels This inspection can only be carried out after shutting down and cleaning the inside of the vessel.
- The main contents of the inspection not only include all the contents of the external inspection but also inspect the corrosion and wear of the inner and outer surfaces;
- Use the naked eye and a magnifying glass to check all welds, head transition areas, and other stress concentration parts for cracks, and if necessary, use ultrasonic or radiographic flaw detection to check the internal quality of the welds;
- Measure the wall thickness, if the measured wall thickness is less than the container wall thickness, the strength check should be re-checked, and measures for depressurization or repair should be proposed;
- For containers that may cause changes in the metallographic structure of metal materials, metallographic inspection shall be carried out if necessary;
- The main bolts of high-pressure and high-pressure vessels should be inspected for cracks by using magnetic powder or coloring.
Through internal and external inspections, the reasons for the defects detected should be analyzed and suggestions for handling are proposed. Recheck after repair.
The inspection period for the inside and outside of the pressure vessel is once every three years, but the inspection period for the container with a strong corrosive medium and highly toxic medium should be shortened. The inspection period should also be shortened for containers with serious defects found during operation and containers with poor welding quality and unknown corrosion resistance of the material to the medium.
In addition to the above-mentioned inspection items, the comprehensive inspection of pressure vessels should also carry out a pressure test (generally a hydraulic test).
Carry out non-destructive inspection spot check or all weld seam inspections on main welds. However, for containers with very low pressure, non-flammable or non-toxic, non-corrosive medium, if no defects are found, the non-destructive inspection may not be performed after obtaining a certain experience. The comprehensive inspection cycle of the container is generally carried out at least once every six years.
For qualified containers containing air and inert gas, the comprehensive inspection period may be appropriately extended after the user experience and one or two internal and external inspections have been obtained to confirm that there is no corrosion.