Due to the weak technical strength and poor quality awareness of some gas tank manufacturing units, some safety performance problems occurred in the manufacturing process, which are summarized as follows.
(1) Design: The manufacturing unit does not carefully review the drawings and does not record the plans, so that the design drawings sometimes do not meet the standard requirements, resulting in products that do not meet the regulatory requirements.
(2) Manufacturing and inspection process: The manufacturing and inspection process lacks content requirements, the preparation and verification of the manufacturing and inspection process is not signed, and there is no approval after deviating from the process.
For example, the welding process with a plate thickness of 32mm only specifies the welding parameters for each side, but does not specify the number of welding layers and passes for each side. Can not guide welding production.
(3) Evaluation of welding process: 1 When evaluating the welding process, the crack resistance test is not carried out first. In the welding process evaluation, the properties of materials and electrodes are only standard values, and there is no actual re-inspection data. Part of the stainless steel welding process evaluation did not carry out the intergranular corrosion test. 2 Weld assessment does not cover the entire process. The heat exchanger tube sheet is 40mm, which is simplified to 10mm, and the connection with the tube sheet is simplified as a butt weld of a corner joint. The thickness of the welding evaluation test piece was 12 mm, and 40 mm was uncovered. The manufacturing unit mistook the corner seam for a fillet seam. In fact, a fully welded corner joint is a butt weld.
The head of the tank is spliced and heat-pressed. There is no heat-treating weld evaluation for the transition temperature. The welding of the floating head flange and the heat exchanger head shall be heat treated according to the regulations. Due to the large difference in plate thickness, the weld evaluation cannot cover the whole process. For example, the flange thickness is 40mm, the head thickness is 10mm, and the material is 16MnR. The heat treatment holding time of weldment shall be at least 1h, and the heat preservation temperature shall be at least 0.5h for 10mm thick welding evaluation. According to JB4708, the holding time for welding evaluation shall not be less than 80% of the heat treatment of the weldment. 80% of 1h is 0.8h, which is greater than 0.5h. This weldment evaluation does not cover the weldment.
(4) Material management: 1. Material storage management is chaotic, regardless of furnace batch number or grade. Regardless of whether there is an inspection, there is no distinction between qualified and unqualified, and they are stacked together. 2 Marking of materials, some material markings cannot distinguish furnace lot numbers, markings are not transplanted, a large number of cutting remaining boards are stored in workshops without material markings, no need to return to the program. The materials are reviewed, and some materials have no original material certification, and the copies do not have the signature and inspection seal of the dealer legal person. 3 Use of pads
(5) Non-destructive testing: (1) The content of the non-destructive testing power of attorney is incomplete, and the spot inspection location is not clear during partial inspection, resulting in insufficient inspection and detection rate.
The vertical container bracket is directly welded on the cylinder block and cylinder head with angle steel, but there are gaps on both sides of the angle steel at the simplification and header welds, and the two sides of the angle steel are not in contact with the weld, but at this time the angle steel covers the welding.
(6) Product welding test plate: The non-destructive testing of product welding test plate is not evaluated. If there are any defects, the defect site cannot be sampled. There are heat treatment requirements, and the test plate is not heat treated with the product.
(7) Production equipment: some units are in good condition, but the voltmeter, ammeter and pressure gauge have not been verified.
(8) Welder problem: 1 A container factory has not been in production for more than 10 months, and the welder did not test when it was put into production. 2 The container is a composite plate of 16MnR and 1Gr18Ni9Ti. Welders holding 16MnR and 1Gr18Ni9Ti weldments cannot weld 16MnR and 1Gr18Ni9Ti composite plates. According to "Boiler and Pressure Vessel Pipeline Welder Examination Management Regulations", the welding of clad plates should be qualified for surfacing welding.
(9) Hydraulic test: 1 There are no requirements for the hydraulic test process and related procedures. There are no provisions for pressure test medium and safety protection. There is no laboratory test report for chloride content analysis. 2 Hydrostatic pressure test of the
Reactor. After the inner cylinder was fabricated, the jacket was welded without the hydrostatic pressure test, resulting in irreparable defects.
(10) Outsourcing issues: (1) The outsourcing agency does not review subcontractors, and does not file with the issuing agency: (2) Physical and chemical rights do not specify testing methods and standards; (3) Only when the steel number or grade is not given. out the material. Specific requirements such as no sulfur, phosphorus content requirements and so on. Caused by the excess of some harmful elements; 4 The thickness of the head does not meet the requirements
April 19, 2022
