The pressure vessel is a type of equipment widely used in actual production and life. In specific production, it is not only necessary to be able to do its design in strict accordance with the standard specifications, but also to pay attention to its manufacturing process. In this regard, it is necessary to be able to grasp the common problems in the manufacturing process and to solve and control the problems in a targeted manner.
3 Problems
Process control problems
In the manufacturing process of pressure vessels, the technological process should be strictly followed, and materials should be selected, processed, and manufactured according to national standards. If the process flow and national standards are violated in any link, it is very easy to cause pressure vessel quality problems and lead to major production safety accidents. There is no complete production process established in the production process, the operators are not familiar with the process, have no concept of quality and responsibility, substitute the inferior for the superior in the selection of materials, various mistakes occur in the manufacturing process, the operation is not standardized, the production concept is backward, and the operation is arbitrary. , causing product defects and quality problems. The work unit does not have a complete supervision and training mechanism, and the responsibilities of personnel are not clear, which is prone to various irregular operations.
Pressure Vessel Deformation Problems
The pressure vessel is deformed due to the abnormal overall structure of the pressure vessel, the inconsistency of the size specification of a certain part or several parts with the drawing requirements, or the failure of its components to meet the national standards. One kind of deformation is mainly caused by stress, mainly including deformation caused by flame cutting, deformation caused by processing instability, welding deformation and heat treatment deformation, etc.; one is caused by errors during processing, including blanking errors, forming errors, assembly errors, etc. Some deformations can be corrected, while others cannot be corrected, resulting in waste. Taking steel as an example, the steel itself has the properties of high hardness, high-temperature resistance, and not easy to deform, and is the main material for manufacturing steel pressure vessels. However, the phenomenon of torsion and bending deformation is easy to occur during the transportation process, which will affect the precision of the parts during the cutting process, and also affect the overall quality of the pressure vessel, resulting in a certain degree of waste of raw materials. Most of the pressure vessels are machined, and assembly will also generate a lot of coercive force. The accumulation of the coercive force is easy to form internal stress, and it is easy to form deformation or even cracks.
Cracks in the container
Metallic materials in pressure vessels can crack under the influence of temperature, corrosive environment, or tensile stress. Cracks are harmful to pressure vessels, with complex causes, diverse shapes, and easy expansion. These cracks mainly include stress corrosion cracks due to corrosion and tensile stress, cold cracks generated when the welding is cooled to a lower temperature, and hot cracks formed by low melting point crystallization generated in the last cooling area of the weld, and no after welding. Cracks, but reheat cracks when reheated to 550-600°C, lamellar tears in a cross and corner joints, are due to delaminated inclusions inside the rolled steel.
Solution
Pressure Vessel Manufacturing Process Control
First of all, the material selection of the pressure vessel must meet the standards, the material must be corrosion-resistant, and the appropriate material should be selected according to the required parameters of the pressure vessel and considering the operating conditions of the equipment. In the manufacture of pressure vessels, operators must strictly implement process discipline, deeply root their safety responsibility awareness, and establish quality awareness. The manufacturing unit should strengthen the training of the relevant knowledge and skills of the staff, introduce advanced production management experience, establish a strict process management control system, guide and teach on-site through excellent operators, and verify the entire manufacturing process through further practical professional skills training. important parameters and product characteristics that need to be controlled before entering the manufacturing process. In the manufacturing process, it is necessary to strictly implement the process requirements, strictly follow the production process, clarify the quality responsibility, preserve the original data of the complete production process, and strictly prohibit fraud. A complete process management system is established, and each link strictly follows the processing system.
Prevent deformation of pressure vessels
To prevent the deformation of the pressure vessel, it is necessary to keep the pressure vessel in a controllable state at any time, strictly regulate the production activities according to the manufacturing process and material characteristics, comply with the specifications according to the operating standards, and try to avoid the occurrence of deformation. The manufacturing process of the pressure vessel must comply with the drawings and national standards. Requirements, through the quality improvement of each link, to gradually improve product quality. When the material is cut, it is symmetrically cut, and after the cutting is completed, a flat orthopedic treatment is carried out. In the actual manufacturing process, how to effectively adjust the welding heat input? It is necessary to construct according to the process specification and standard. After the welding is completed, the stress heat treatment should be carried out in time to eliminate the deformation of the pressure vessel to the greatest extent. Relieving internal stress generally also requires heat treatment. When the temperature is balanced, a firewall can be designed at the furnace wall flame nozzle to separate the flame and heat treatment. If the thickness of the outer shell is insufficient, the interior should be strengthened to prevent the container from collapsing.
Prevent pressure vessel cracks
To prevent cracks in pressure vessels, it is necessary to scientifically select vessel materials and welding materials in the production process, pay attention to modification, and improve welding processes and operations. The material inside the weld should be consistent with the material of the container. From farming to manufacturing, we should try our best to avoid the possibility of residual stress, choose steel with few impurities, etc., strictly implement the welding material baking process, and control the assembly quality, and the actual quality of each part. The size of the material must be scientific and reasonable to prevent the problem of strong assembly. Welding should be performed according to the welding process. During the welding process, the hardening of the welding heat-affected zone should be avoided, the cooling time of the weld should be prolonged, and the possibility of low cracks should be effectively reduced.
NDT
Non-destructive testing, also known as flaw detection, is mainly used for weld inspection of pressure vessels. Because non-standard pressure vessels do not use common processes, specifications, and product parameters, process cards must be made and non-destructive testing must be performed. The methods of non-destructive testing mainly include ultrasonic waves, rays, penetration, etc. These methods must require professionals who have passed the national assessment to work on their posts. They can detect the raw materials of the finished pressure vessel, the surface and interior of the weld, and find defects in time to ensure the quality of the pressure vessel.
Epilogue
In the above, we have conducted some research on common problems in the manufacture of pressure vessels. In the actual manufacturing of pressure vessels, it is necessary to be able to avoid problems in the upper part and to ensure the quality of manufacturing and the application safety of vessels by the application of scientific manufacturing methods.