Safety control of the supervision and inspection q

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Safety control of spherical tank supervision and inspection quality (1)

spherical tank is an important storage equipment for liquefied petroleum gas, liquefied natural gas, liquid ammonia, liquid nitrogen, liquid hydrogen, liquid oxygen and other media. Its product quality is related to both enterprise production and personal safety. Once an accident occurs, it will bring huge economic losses to the enterprise and the country. Therefore, it is of great significance to carry out the research on the quality and safety control of spherical tank supervision and inspection

Compared with other storage containers with the same capacity, spherical tanks have the advantages of small net mass, small surface area, less land occupation and short manufacturing turnaround. They are more and more widely used in petroleum, chemical, metallurgical, light industry and other production. Spherical tanks are generally used to store flammable and explosive dangerous media, and are often exposed to harsh environments such as high temperature, high pressure, corrosion and cyclic fatigue loads. Therefore, accidents such as spherical tank cracking, corrosion leakage and structural damage are common. Once the spherical tank has an accident, it will not only seriously affect the economic production and construction, but also may lead to catastrophic accidents. Therefore, the construction and use of 14400 ton spherical tanks with vanadium and titanium production in Chengde in 2016 not only attracted great attention from the industry, but also received extensive attention from governments around the world. Many countries listed it as a government act, and established corresponding inspection institutions to supervise and manage the inspection

the quality and safety control of spherical tank supervision and inspection includes technical data review, structural appearance quality and geometric dimension inspection, spherical tank plate thickness measurement, magnetic particle testing, penetrant testing, ultrasonic testing, radiographic testing, safety accessories inspection, pressure and air tightness test, spherical tank safety assessment, etc. This paper discusses the five links of the quality and safety control process of spherical tank supervision and inspection, as well as the five levels of system documents, standards and specifications, personnel control, system platform and supporting technology, and puts forward suggestions on the protective measures for the safe operation of spherical tanks

1 quality and safety control process of spherical tank supervision and inspection

quality and safety control of spherical tank supervision and inspection, including technical data review

1.1 Technical Data Review

review of construction documents such as spherical tank design documents, construction schemes, welding process evaluation, etc.; review of material certificates and re inspection reports of plates and welding materials used on site; review of qualification certificates of installation units and testing units and welders The qualification certificate of NDT personnel shall be verified

1.2 macro spot check

(1) check the spherical tank structure and consider the influence of box printing on the compressive strength during the welding process. The lap width, butt weld, butt gap, groove angle and the implementation of on-site welding process shall meet the requirements of relevant specifications:

(2) quality inspection of welding joint table. The fillet weld leg size, butt weld width and reinforcement, weld misalignment, undercut, etc. should meet the design requirements:

(3) check the spherical tank body and weld cracks, overheating, deformation and leakage:

(4) check whether the bolts, supports, and drainage devices fall off, damage, failure, and check other relevant construction records:

(5) thickness measurement spot check of steel plates for bottom plates and laminates, Measure the wall thickness of the key parts of the spherical tank

1.3 nondestructive testing inspection

polish the inner surface and weld seams of the spherical tank and the welding traces of the two sides and the inner surface and fixture, and clean up the rust and other debris. Conduct magnetic particle testing with fluorescent magnetic particle suspension. Determine the inspection proportion of the appearance of the butt weld according to the design, manufacturing, service parameters of the spherical tank, the material of the spherical shell plate and the inspection results of the inner surface. If defects are found, Properly expand the proportion for testing: check the internal and external surfaces of the fillet welds between column legs and spherical shell plates, Manholes, and nozzle fillet welds. However, the communication between the butt weld experimental machine that is difficult to perform magnetic particle flaw detection and the computer is generally RS232 serial communication mode, and penetrant testing is used at the welding trace of tool fixtures; Digital ultrasonic instrument is used to detect the butt weld

determine whether to carry out spherical tank radiographic testing, acoustic emission testing, TOFD testing, eddy current testing, etc. according to the quality, defects, corrosion and service conditions of spherical tank design, manufacturing and installation

1.4 safety accessories inspection and pressure and air tightness test

check whether the factory quality certificate, certificate of conformity, specification, model, accuracy, quantity, measurement identification, etc. of the pressure gauge, emergency shut-off valve, safety valve, liquid meter, temperature measuring instrument and other accessories of the spherical tank meet the requirements of relevant regulations, and check whether the calibration report is within the validity period

use clean water or other safe media to carry out pressure withstand test at the maximum working pressure of 1.25 times of water pressure (1.15 times of air pressure); Air tightness test shall be carried out with compressed natural gas or nitrogen

1.5 safety evaluation of spherical tanks

safety evaluation of spherical tanks is based on the detection of spherical tanks. It studies the degradation law of tank material performance and the dynamic development law of various defects that the proportion of plastic packaging in the total output value of the packaging industry has exceeded 30% in the spherical market. Through model test and theoretical mechanical calculation, the fracture toughness, maximum allowable pressure, residual life, residual strength, etc. of spherical tanks are determined, It provides a scientific basis for the safe operation and maintenance of spherical tanks

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