Pipeline inspection standard
The inspection and test work of pressure pipeline includes: appearance inspection, thickness measurement, nondestructive testing, hardness measurement, metallographic examination, pressure test, etc. Magnetic particle testing is a common nondestructive testing method. The ability of magnetic particle detection is not only related to the intensity of applied magnetic field, but also related to the direction of defects, the depth-width ratio of defects, the shape of defects, the shape, size and surface state of workpieces, and the parts where defects may occur. Therefore, there are various magnetization methods.
Pipeline characteristics
1. Pressure pipeline is a system, which is interrelated and affects each other.
2. The length-diameter ratio of pressure pipeline is large, which is easy to lose stability, and the stress situation is more complicated than that of pressure vessel. The fluid flow state in the pressure pipeline is complex, the buffer space is small, and the working frequency is higher than that of the pressure vessel (such as high temperature, high pressure, low temperature, low pressure, displacement and deformation, wind, snow, earthquake, etc.). ).
3. There are many kinds of pipeline components and pipeline supports, each material has its own characteristics and specific technical requirements, and the selection of materials is complicated.
4. There are more possible leakage points on the pipeline than on the pressure vessel. Generally, a valve has five places.
5. There are many types and quantities of pressure pipes, and there are many links in design, manufacture, installation, inspection and use management, which are quite different from pressure vessels.
Requirements and technology of pipeline welding
I. Personnel quality
For pressure pipeline welding, the most important person is the welding engineer, followed by the quality inspector, the wounded and the welder.
1. The welding engineer is an important person in charge of pipeline welding quality, mainly responsible for the compilation, review and release of a series of welding technical documents. Such as weldability test, welding procedure evaluation and report, welding scheme and welding work instruction, etc. Therefore, welding engineers should have rich professional knowledge and practical experience, strong sense of responsibility and professionalism. Often go deep into the site to grasp the first-hand information of pipeline welding in time; Supervise the welder's awareness of observing welding process discipline; Assist the project leader to ensure the welding quality of pipelines; Support and guide the inspection work of quality inspectors and the wounded, and guide and supervise the storage, baking and distribution of covered electrode.
2. The quality inspector and the wounded are the personnel who directly inspect the welding quality, and each of their inspection data plays an important role in evaluating the welding quality. Therefore, the quality inspector and the wounded must first pass the training and examination of the higher authorities, obtain the corresponding qualification certificates, hold relevant certificates, and be familiar with relevant standards, procedures and norms. We must also have a good professional ethics, enforce the law impartially, strictly grasp the standards and scales of inspection, and do not be emotional or resort to deceit. Only in this way can the authenticity, accuracy and authority of inspection results be guaranteed, thus ensuring the authenticity and reliability of pipeline welding quality.
3. Welder is the executor of welding process and the operator of pipeline welding. Therefore, the quality of welders is of decisive significance to ensure the welding quality of pipelines. A good welder should have good business skills. Skilled practical skills can not be developed overnight, but can be matured through practical training or even intensive training. Finally, he can pass the exam to obtain the corresponding welding qualification. The standards and regulations related to this point have clearly defined the welder's skills and welding scope. A good welder must also have good professional ethics, professionalism and a strong sense of quality, in order to consciously operate according to the requirements stipulated in the welding process. Concentrate on the welding process, not be disturbed by external factors, not let go of any small link that affects the welding quality, and be meticulous, and finally get excellent weld quality.
4. As managers, we should establish the files of welders with certificates. In addition to mastering the qualified items of certified welders, we should also pay attention to the daily performance assessment of welders. Regular spot checks can be made, and the welding work of each welder, including the statistics of the first pass rate after X-ray inspection, can be stored in the welder's file. At the same time, a reward and punishment system is formulated to reward welders with stable welding quality. This provides a basis for managers to evaluate welders. For welders with good and stable quality, they can be arranged as welding tasks for important pipelines or important processes in pipelines to ensure welding quality.
Second, the welding material
The influence of welding materials on welding quality is self-evident, especially the covered electrode and welding wire directly entering the weld will directly affect the composition and mechanical properties of the weld alloy elements, which must be strictly controlled and managed. The selection of welding materials shall follow the following principles:
① It should match the mechanical properties and chemical composition of the parent material.
② The complexity and rigidity of weldment, preparation of welding groove, position of welding seam, working conditions and performance of weldment should be considered.
③ Operation technology, equipment and construction conditions, labor productivity and economic rationality.
(4) the technical ability and equipment ability of welding workers. In addition, according to the requirements of pressure pipeline welding, welding materials should be managed by primary and secondary libraries. The storage location, storage, drying, distribution and recycling of welding materials on the construction site shall be strictly implemented in accordance with relevant regulations. Ensure the quality of welding materials used, ensure the stability of welding process and the composition and performance of weld meet the requirements.
Third, the welding equipment
1. The performance of welding equipment is an important factor affecting pipeline welding. The selection should generally follow the following principles:
(1) Meet the welding technical performance requirements necessary for workpiece welding.
(2) Select and purchase equipment with high credibility produced by manufacturers with national compulsory CCC certification, and compare the comprehensive technical indicators of welding equipment, such as welding machine input power, temporary load rate, main components inside the main engine, appearance, etc.
③ Consider factors such as efficiency, cost and maintenance cost.
(4) In order to reduce the labor intensity of welders and improve production efficiency, it is particularly important to choose special equipment with better comprehensive performance indicators as far as possible. Many welding equipment manufacturers at home and abroad are committed to special planes and have made brands. Therefore, the principle of choosing welding equipment is to choose special equipment, and the equipment performance index is excellent. Only in this way can the stability and improvement of welding quality be ensured.
2. The maintenance of equipment plays an important role in the smooth progress of welding operation, improving equipment operation rate and ensuring welding quality, and is also a necessary condition to ensure the safety of operators. Therefore, welders should correctly use and carefully maintain the equipment they operate; When problems are found, deal with them in time, leaving no hidden dangers. For parts that are often damaged, reserve them in advance and repair the equipment at the first time. In addition, the current and voltmeter on the equipment are the basis for evaluating the welder's process parameters, and should be fully equipped and guaranteed within the approved validity period.
Fourth, the welding process
1. Compilation of welding process documents. Welding process documents are technical regulations or measures to guide welding operations, which are generally completed by technicians. According to the procedures and requirements of welding process documents, there are mainly welding test and welding process qualification, welding process instruction or welding scheme, welding work instruction, etc. Weldability test is generally carried out for new materials or new processes. Weldability test is the basis of welding procedure qualification, that is, any welding procedure qualification should be carried out after the welding test is qualified or the welding characteristics and process requirements are mastered. After the welding process is qualified, the process instruction can be directly used to guide welding production. For major or important pressure pipeline projects, the welding scheme can also be compiled according to the welding procedure instruction or welding procedure qualification report to comprehensively guide the welding construction.
2. Execution of welding process documents. Because the welding procedure instruction and welding procedure qualification report are managed as technical documents to guide production practice, they are generally kept and managed by technicians. Therefore, when welding pressure pipelines, it is often necessary to compile welding operation instructions, explain all the principles, specific technical measures and process parameters of pipeline welding clearly, and distribute the welding operation instructions to the welder team, so that all welders can effectively implement them in actual welding after learning and mastering their requirements. The welder's construction behavior can be regulated within the requirements of relevant technical standards and process documents, thus truly ensuring the welding quality of pressure pipelines.
In order to ensure the welding quality of pressure pipes, besides strictly implementing the design regulations and welding process documents, the welding quality inspection must also be carried out in strict accordance with the provisions of relevant national standards and norms. Welding quality inspection includes pre-welding inspection (material inspection, groove size and quality inspection, assembly quality inspection and groove cleaning inspection, welding environment and pre-welding inspection, etc.). ), intermediate welding inspection (positioning welding quality inspection, weld line energy measurement and recording, weld level and interlayer quality inspection) and post-welding inspection (appearance inspection and nondestructive inspection). Only by strictly controlling inspection and supervision can the process discipline be implemented, so that the welding process is always under control, thus effectively ensuring the welding quality of pressure pipes.