Due to the weak technical strength of
LPG Storage Tanks manufacturing units and the poor quality awareness, some safety performance problems have arisen in the manufacturing process and are summarized below.
(1) Design: The manufacturing unit does not carefully review the plans and does not plan to record the plans, making the design drawings sometimes do not meet the standard requirements, resulting in products that do not meet the regulatory requirements. The main problems are: 1 the diameter of the opening exceeds half of the cylinder: a diameter of the cylinder is 1800, and the diameter of the opening is 1200. According to GB150 regulations: The diameter of openings should not exceed 1000mm. Its technical requirements: According to GB150 manufacturing and inspection, it is not in compliance with the regulations. GB150 stipulates: The pressure components that cannot be determined by this standard are allowed to be designed by other methods but must be evaluated and approved by the National
Pressure Vessel Standardization Technical Committee. However, no approval was found. Insufficient proportion of 2 ray detection: The diameter of a certain cylinder is 350350, and the ratio of ray detection is 20%. According to the “Supervision Regulations for Pressure Vessel Safety Technology”, containers larger than ?300 should be inspected and the inspection holes should be manholes, hand holes, and cocks. Otherwise, 100% RT testing should be performed. Process piping cannot be used as an inspection hole. Regular inspection. 3 The pressure of the hydrostatic test is lower than the specified value: the design pressure of a gas storage tank is 1.1 MPa, the design temperature is 200°C, the material is Q235B, and the test pressure is 1.37 MPa. According to the provisions of GB150, the hydraulic test pressure Pt=1.25[a]/[a]tP, the calculated test pressure should be 1.4MPa, and the correction factor is not taken into account in the design.
(2) Manufacturing and inspection processes: The manufacturing and inspection process lacks content requirements, and the manufacturing and inspection process preparation and verification are not signed, and there is no approval after deviating from the process.
For example, a welding process with a plate thickness of 32 mm only specifies the welding parameters for each side but does not specify the number of welding layers and the number of passes for each side. Cannot guide welding production.
(3) Evaluation of welding procedure: 1 When the welding procedure is evaluated, the crack resistance test is not conducted first. In the evaluation of the welding procedure, the properties of the material and the electrode have only their standard values, and there is no actual recheck data. Some stainless steel welding process evaluation did not conduct intergranular corrosion test. 2 Weld assessment cannot cover the entire process. A heat exchanger tube plate is 40mm, simplified 10mm, Simplified and tube plate connection is a corner joint butt weld. The thickness of the welded evaluation test piece is 12mm, failing to cover 40mm. The manufacturing unit misunderstood the corner seam as a fillet joint. In fact the fully welded corner joints are butt welds.
The head of a tank is spliced and hot pressed. There is no heat treatment welding evaluation on the transition temperature. According to JB4708, the hot stamping head undergoes the heat treatment of the upper transition temperature, and important variables are changed. There should be a heat treatment welding evaluation of the transition temperature.
The welding of floating head flanges and heads of a heat exchanger shall be heat treated according to regulations. Because of the large difference in plate thickness, the weld evaluation cannot cover the entire process. For example, the flange thickness is 40mm, the head thickness is 10mm, and the material of
LPG Storage Tanks is 16MnR. The heat-treatment holding time of the weldment is at least 1h, and the heat-retention temperature of the 10mm-thick welding evaluation is at least 0.5h. According to JB4708, the heat preservation time for welding evaluation should not be less than 80% of the heat treatment of the weldment. 80% of 1h is 0.8h, greater than 0.5h. This kind of welding assessment cannot cover this weldment.
(4) Material management: 1 The storage management of the material is confusing, and the batch number or brand of the furnace is not divided. No matter whether the inspection has been conducted or not, there is no distinction between qualified and unqualified, and piled together. 2 The marking of materials, some material marks can not distinguish the furnace batch number, the mark is not transplanted, a large number of cutting remaining plates are stored in the workshop without material markings, and no returning procedures are required. Re-examination of materials, some material without original material certificate, copy without signature of distributor legal person and inspection seal. 3 The use of welding consumables, some units welding rods are used, the recycling system is not strict, and some of the welding rods used for welding are different from the welding batch number of the welding electrodes. Some of them are used by multiple people.
(5) Non-destructive testing: (1) The contents of the non-destructive testing power of attorney are incomplete, and the location of spot checks during local inspection is not clear, resulting in insufficient ratio of missed detection and detection. The patch map in the test report does not clearly reflect the test site. 2RT detection ratio is not enough: a sub-cylinder is ?273, 100% RT detection. However, there are only four 300mm negatives in the NDT report. According to JB4730: the effective length of the film is 110mm, 100% RT detection should have 10 110mm negative film missed.
A vertical container support is welded directly to the cylinder body and head with angle steel, but the two sides of the angle steel have notches at the Simplified and Header welds, and the two sides of the angle steel are not in contact with the weld, but the angle steel covers the welding at this point. Sew. RT testing should also be done here.
(6) Product welding test plate: Non-destructive testing of the product welding test plate is not evaluated. If there is any defect, the defect site cannot be sampled. With heat treatment requirements, the test plate is not heat treated with the product.
(7) Production equipment: Some
LPG Storage Tanks equipment is in good condition, and voltmeter, ammeter, and pressure gauge are not verified.
(8) Welder problems: 1 A container factory was not produced for more than 10 months, and the welder did not take the test when it was put into production. 2 A container is a composite panel of 16MnR and 1Gr18Ni9Ti. Welders holding 16MnR and 1Gr18Ni9Ti welding items cannot weld composite panels of 16MnR and 1Gr18Ni9Ti. According to the "Boiler Pressure Vessel Pipe Welder Exams and Management Rules", the welding of composite plates shall be qualified for surfacing.
(9) Hydraulic pressure test: 1 There is no requirement for hydraulic pressure test process and related procedures. There is no regulation for pressure test media and safety protection. There is no laboratory test report for chloride ion content analysis. 2 Hydrostatic pressure test of the reactor. After the inner cylinder was manufactured, the jacket was welded without hydrostatic pressure test, causing the defect to fail to be repaired.
(10) Outsourcing issues: (1) The external committee does not review the subcontractors, and does not file with the issuing agencies: (2) The physical and chemical powers do not specify the standards for the test methods; (3) The materials are given only when the steel number or grade is not given. Specific requirements such as the absence of sulfur, phosphorus content requirements. Some of the harmful elements caused by excessive; 4 head thickness does not meet the requirements, according to JB4746 regulations, the minimum thickness of the head should be greater than the nominal thickness minus wall thickness additional amount.
A liquefied petroleum gas storage tank is ?1000 and its design thickness is 12mm. The head is pressed with a 16MnR steel plate, and its wall thickness reduction is about 1 mm, which is greater than the negative deviation of the steel plate. It should be pressed with 14mm 16MnR steel plate, and its minimum wall thickness meets the design requirements.
Reid brand gas tanks produced by Shuyang Reid Pressure Vessel Company are underwritten by China Life Insurance, and the product quality is trustworthy! For more information about gas tanks on the website of Ruiyang Pressure Vessel Co., Ltd., you can also contact us for information on the
LPG Storage Tanks.
