Pressure vessels in the leading cities of chemical industry and petrochemical industry are mainly used for heat transfer, mass transfer, reaction and other technological processes, as well as storage and transportation of pressurized gas or liquefied gas; It is also widely used in other industrial and civil fields, such as air compressors.
Various special compressors and auxiliary machines of refrigeration compressor (cooler, buffer, oil-water separator, gas storage tank, evaporator, liquid refrigerant storage tank, etc.). ) are all pressure vessels.
Extended data:
Inspection of pressure vessels:
External inspection:
Also known as in-service inspection, the main contents of inspection include: whether there are cracks, deformation, leakage, local overheating and other abnormal phenomena on the outer surface of pressure vessels; Whether the safety accessories are complete, sensitive and reliable; Whether the fastening bolts are intact and completely tightened; Whether the foundation is sunken or inclined, and whether the anticorrosive coating is damaged.
External inspection is not only the work of inspectors, but also the routine inspection items of operators. Found the phenomenon that endangers safety (such as cracks, deformation, serious leakage, etc.). ) should be stopped in time and report to the relevant personnel.
Internal and external inspection:
Internal and external inspection of pressure vessels. This inspection can only be carried out after parking and cleaning the inside of the container. The main contents of inspection include not only the whole contents of external inspection, but also the corrosion and wear of internal and external surfaces;
Check all welds, head transition zone and other stress concentration parts for cracks with naked eyes and magnifying glasses, and check the internal quality of welds with ultrasonic or radiographic inspection if necessary; Measure the wall thickness.
If the measured wall thickness is less than the minimum wall thickness of the container, the strength should be checked again, and the depressurization or repair measures should be put forward; Metallographic inspection shall be carried out when necessary for containers that may cause changes in the metallographic structure of metal materials; The main bolts of high-pressure and ultra-high-pressure vessels shall be inspected for cracks by magnetic powder or coloring.
Through internal and external inspection, the causes of the defects detected are analyzed and the treatment suggestions are put forward. After repair, it should be re-inspected. The internal and external inspection cycle of pressure vessels is once every three years, but the inspection cycle of vessels with strong corrosive media and highly toxic media should be shortened. For containers with serious defects found in operation and containers with poor welding quality and unknown corrosion resistance of materials to media, the inspection period should also be shortened.
Comprehensive inspection:
In addition to the above inspection items, the comprehensive inspection of pressure vessels should also carry out pressure tests (generally water pressure tests). Non-destructive inspection and spot check of all welds shall be carried out for the main welds.
However, for containers with low pressure, incombustible, non-toxic and non-corrosive medium, if no defects are found, nondestructive testing can be omitted after gaining some experience in use.
The comprehensive inspection cycle of containers is generally carried out at least once every six years. For qualified containers filled with air and inert gas, the comprehensive inspection cycle can be appropriately extended after gaining experience and confirming that there is no corrosion through one or two internal and external inspections.
References:
Baidu encyclopedia-pressure vessel