Analysis of common problems in the inspection of boiler pressure vessels
Boiler pressure vessel is widely used, in the presence of minor hidden problems often can not be easily found, the operator will continue to use, the degree of risk will be greatly increased, causing a major threat to personal safety. Therefore, pay attention to the boiler pressure vessel inspection, timely detection of problems, take a scientific and reasonable approach to eliminate hidden dangers, in order to avoid accidents. This paper analyzes the problems of boilers in the inspection and testing, summarizes the solution to the problem, to improve the quality of the inspection of boiler pressure vessels, has a certain guiding significance.
Boilers are used in working conditions accompanied by combustion, explosion and high pressure, and are important equipment in the special equipment industry. Boilers in the process of operation will accumulate a large amount of heat, generate high pressure, must be accurate and timely control, the correct disposal of the entire process, in order to operate safely and reliably.
The primary purpose of the boiler inspection is to inspect the boiler itself for defects, such as the strength of the production process, the height of the standard, the aging, corrosion, cracks, leaks and other safety hazards in the process of use. The second is to test the use of personnel and inspectors to master the degree of regulations, as well as operational skills and inspection level. In addition, also test the relevant personnel’s awareness of safety responsibilities.
The content of the inspection
External inspection mainly includes welding seams, manholes, hand holes, etc., whether there is water leakage; the highest allowable working pressure of the pressure gauge is marked with a red line, whether the inspection cycle is in line with the provisions, with or without a lead seal to indicate how accurate, and standard pressure gauge for calibration; in the boiler operation to verify the opening degree of the safety valve and back to the seat pressure, as well as the presence of a lead seal; the water level gauge is clear, whether the connection tube is smooth; whether the lighting equipment The lighting equipment is intact; whether the automatic control and protection devices are sensitive and reliable, and whether the automatic or manual control can be converted normally. The usual inspection cycle is once a year, but also according to the actual operation of the boiler, by the staff to change the frequency of testing.
Internal inspection is usually once every two years. If there is a sudden failure, the staff should be decisive, immediately stop operation, and in accordance with the actual situation of the internal inspection work to ensure safety. The main content of the internal inspection is to stop running the boiler, so that it is in a static state, open the door, check the bottom of the barrel, water-cooled wall tubes, furnace tubes, superheater, etc. there is no bulging, dome bending and other deformation.
Water pressure inspection
Pressurize the boiler before operation to test the strength and tightness of the internal structure. After strict water pressure testing, make sure there is no problem before running the boiler.
Safety testing is mainly for the materials used in the boiler. Determine the material manufacturer has the qualification to produce steel for pressure vessel boiler, and to meet the requirements of the corresponding level of pressure vessel. At the same time, the welding quality of the boiler pressure vessel manufacturing is tested to assess the overall safety and stability of the equipment. Therefore, pay attention to the procedures and related documents of the audit and calibration of welding, the use of standard types of materials, the selection of appropriate testing methods for different parts, and the timely remedy of problems found.
Boiler pressure vessel inspection process common problems
Quality problems in the design and manufacturing process
In the current production process, the boiler manufacturing process and design requirements are still inadequate, the design deficiencies are difficult to make up with the process, and the development of the process also lacks innovation, and often does not meet the design requirements. Especially when different manufacturing materials are taken, it will lead to different production processes, resulting in deviations in the quality of the product. And boilers often operate under high pressure and high temperature, in the production process due to improper material selection and manufacturing process methods, or because manufacturers use materials that do not meet the standard provisions, etc., can cause all kinds of safety accidents.
Defects in the process of use
Boiler components are prone to corrosion in the process of use, and when alternating stresses act for a long period of time, cracking problems will arise. According to the site inspection found that austenitic stainless steel is susceptible to corrosion, especially in the neutral layer inside the boiler bend pipe, by analyzing the corrosion site, the crystalline phase change is found. Mechanical fatigue can also lead to fatigue cracking during use. The chances of fatigue cracking increase greatly when stress concentrations occur at specific sites. Initial cracks are not easily detectable and very small, and as the use time increases, the cracks increase and grow, as shown in Figure 1, and later cracks form tangential cracks. In addition, mechanical fatigue also produces creep cracks. After the boiler is used for a period of time, it is affected by temperature and stress, and deformation occurs, and the phenomenon of material separation is extremely obvious in the heat affected and high strain areas. Eventually there are cracks and holes appear, producing safety hazards.
Safety management problems
Figure.1 Fatigue Cracking
The main responsibility for implementing the boiler in the process of manufacture and use by the producer is the enterprise. However, some problems usually arise due to the lack of awareness of safety responsibility of enterprise leaders and management confusion, mainly in two aspects. First, after the purchase of boilers and pressure vessels, enterprises do not apply for the use of registration certificates, not to mention the scheduled inspection, some even do not have the daily use and maintenance skills, resulting in a waste of property, and in serious cases, resulting in safety accidents. Secondly, there is no dedicated management equipment, and boiler-related materials are missing and cannot be inspected. These will cause the boiler can not be regularly inspected in accordance with the requirements, more detrimental to the maintenance of equipment, which can easily lead to accidents.
low technical competence of inspection personnel
The level of knowledge and inspection skills of boiler inspectors determines the quality of inspection. If the theoretical knowledge of the inspector is not solid, the relevant laws and regulations can not be understood in depth, it will cause the slackening of safety awareness. Even if you see problems and defects, you will not be able to reasonably elaborate because of the lack of knowledge reserves, or even a wrong judgment or outright ignore, do not realize the danger and seriousness of the matter, easy to cause safety accidents. Only a solid theoretical foundation, familiar with the specific operational inspection process, with a certain amount of practical experience, and strict compliance with the norms, in order to reduce the chances of accidents.
Boiler pressure vessel inspection recommendations
Improve the quality of design and manufacturing
Before using the boiler pressure vessel, the user should choose a qualified manufacturer, provide the use of parameters, communicate with the manufacturing company for the use of working conditions, the key parts should be emphasized. Designers need to follow the customer’s needs, strictly follow the national standards and the corresponding design specifications, carefully analyze, adopt reasonable technical processes and materials, fully review the drawings, and improve the design quality. In the entire manufacturing process, strict testing in accordance with the process flow, division of labor and coordination, to avoid the quality of the boiler because of the manufacturing process and many other problems, resulting in safety risks.
In the process of use, to ensure the safe operation and stability of the equipment, inspectors should be strictly investigated on the weld seam and other parts. Inspectors should understand the common defects of boilers in the process of use, and master nondestructive testing techniques, familiar with the advantages and disadvantages of various testing techniques, so as to ensure that the boiler pressure vessel in industrial production can have a safe use.
Pay attention to safety management
Boiler pressure vessel in the use of the process will have a lot of personnel involved. Managers should strengthen the cultivation of safety awareness of boiler users, establish a reasonable safety management system, and create a safe working environment. Managers and equipment users should coordinate the operation of equipment and pending inspection planning, manage equipment instructions, technical specifications and other relevant inspection materials, and keep timely and truthful records of equipment maintenance and operation. Reasonable arrangement of inspection time, regular inspection and inspection of the boiler, focusing on the presence of cracks, clarify the causes of cracks, and take reasonable measures to ensure the safe operation of the boiler.
Improve the comprehensive ability of inspection personnel
The staff of the boiler pressure vessel inspection must be professionally trained to learn the professional knowledge and skills of the inspection work, familiar with the process of testing. At the same time, the ability to develop a testing program, the boiler operating conditions, damage to the location and cause of failure to make a scientific and reasonable assessment; skilled in the use of testing instruments and the use of a variety of testing methods, and make good preparations before testing. For boilers and pressure vessels operating under special conditions, there should be a perfect emergency rescue plan, and do a good job of rehearsing and taking safety precautions according to the emergency plan. In addition to theoretical and skills training, ideological education should not be relaxed, to strengthen the professional ethics of the inspectors, to enhance the sense of responsibility, and to prevent human factors to bring adverse effects on the boiler inspection work.
In summary, for potentially dangerous boiler pressure vessels, regular inspection should be carried out, a reasonable management system should be established, awareness of safety responsibilities should be raised, and a team of skilled professionals should be trained to ensure safe production and the safety of people’s lives and property.
Author: Jian-dong Gong
Source: Network Arrangement – China Boiler Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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-  Wang Yanbing. Analysis of common problems of boiler pressure vessel inspection [J]. Chemical Management,2016(17):291.
-  Wang Xin. Analysis of cracking problems in boiler, pressure vessel and pressure pipe inspection [J]. Inspection and testing,2020(14):55-56.
-  Han Zhongmei. Cracking problems in boiler pressure vessel and pressure pipe inspection and preventive treatment methods [J]. China Equipment Engineering,2020(06):124-126.