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1.Application status
Infrared thermal imaging technology is a technology that converts invisible infrared radiation energy into visible temperature field images, and uses different colors to represent different temperatures. Since the 1970s, after decades of development, it has rapidly extended from the military field to the civilian field. Due to the rapid development and popularization of this technology, the cost of the instrument has been greatly reduced, and the infrared thermal imager is no longer a "noble" device. Infrared thermal imaging technology has become the most widely used testing technology in addition to the five conventional nondestructive testing of ultrasonic, ray, eddy current, magnetic particle and penetrant testing. Its rapid popularization also benefits from the following characteristics:
- Non contact remote sensing detection does not affect the measured object and is safe to use
- The detection is real-time and convenient, and the measured objects can be scanned and imaged in real time without leakage one by one
- The detection requirements are low, and it can detect objects in the environment of motion, strong magnetism, chemical atmosphere and easy corrosion
- The detection results are objective and intuitive, and the two-dimensional infrared thermal image visually shows the temperature field of each point of the tested object
With the development of society, the requirements for production safety and production process optimization have increased. For important equipment and facilities, fire fighting (FF) management mode is no longer adopted, and preventive maintenance (PM) and preventive predictive maintenance (PPM) are gradually introduced, Predictivemaintenance (PDM) recently, major international companies began to adopt proactive maintenance (PAM). Infrared thermography is one of the most effective tools from FF to PM, ppm, PDM and PAM. In recent years, infrared thermal imaging technology is increasingly used in equipment condition monitoring and fault diagnosis, and has achieved good results. Whether in the United States or China, infrared thermal imagers are used in all walks of life for thermal fault inspection and thermal state measurement, mainly including equipment pre maintenance testing, fault diagnosis, nondestructive testing, energy-saving testing, nuclear power plant safety inspection, building insulation, structural defect detection and leakage moisture detection. The main application fields include pre maintenance and condition monitoring of electric power, metallurgy, petrochemical, construction, boilers and pressure vessels, as well as research and development, quality control and process monitoring, medical treatment, public safety monitoring and military applications. The development of infrared diagnostic technology in China began in the 1980s. The first batch of infrared thermal imagers were used as an important measure of safety production in electric power, petrochemical, metallurgical and other industrial departments, so that it developed rapidly. In the special inspection and petrochemical industry, the national key scientific instrument project "thermoelastic infrared image security detection system" developed by the Institute of metals of the Chinese Academy of Sciences in cooperation with the General Administration of quality supervision, inspection and quarantine and other units has passed the achievement appraisal and the acceptance of the Ministry of science and technology. So far, infrared thermal imaging technology has carried out a large number of tests and achieved fruitful results in many domestic special equipment supervision and inspection units and petrochemical production and testing units.
2.Application in special inspection and chemical industry
Pressure vessels are special pressure equipment with explosion risk. They are responsible for many environmental factors such as high temperature, high pressure, flammable, explosive, highly toxic and strongly corrosive media. Thermoelastic pressure vessels are widely used in all sectors of aerospace and national economy. For the actual stress distribution of pressure vessels under working conditions and the early prediction of potential defects, various conventional methods are powerless, so the safety monitoring and prevention technology of pressure vessels has always been a hot topic in the international research. The thermoelastic effect has been studied tentatively in Britain and the United States, but it is still limited to experimental research. Whether in the special inspection industry or the petrochemical field, temperature control and monitoring can be found everywhere: such as equipment wear, fatigue, crack, fracture, deformation, corrosion, peeling, leakage, blockage, looseness, melting, insulation aging, oil deterioration, adhesion pollution, abnormal vibration, etc. most of these states are directly or indirectly related to temperature changes, many of which cannot be monitored by conventional contact temperature measurement methods, The problem can be solved by using infrared thermal imaging detection technology. The petrochemical industry is an industrial system that carries out extensive work on infrared diagnosis technology. From the 1970s, the Petrochemical Corporation organized the implementation of nondestructive testing to the 1980s, carried out equipment condition monitoring, established a three-level condition monitoring organization based on the head office, the company or the head office and branches, implemented hierarchical management, and first established a first-level organization for rotary machinery diagnosis. Since the 1990s, the development and research of infrared diagnosis technology have been gradually carried out, such as the fault diagnosis of electrical equipment, catalytic cracking unit lining damage and industrial furnaces and kilns; From the initial determination of heat loss in the factory, the scope of its application of infrared detection has been expanding, from infrared detection to infrared diagnosis, from simple diagnosis to precision diagnosis, trend analysis and life prediction. Many units have achieved practical results, among which the more prominent ones are Sichuan general chemical plant, Fushun Petrochemical Company, Changling refinery, Liaoyang Petrochemical Company, Yangzi Petrochemical Company, Daqing Oilfield, Fujian Refining and chemical company, Qilu Petrochemical Company, Tianjin Petrochemical Company, etc. The former Ministry of chemical industry also established an infrared thermal imaging temperature measurement technology center, established a professional group of condition monitoring and fault diagnosis, including infrared thermal imaging technology, formulated the use of infrared thermal imagers to carry out planned and step-by-step regular and fixed-point detection of production equipment, for important and key equipment, set up precision detection points, and establish equipment detection files, so as to make correct judgments and analyze the deterioration trend in case of equipment failure.
3.Application case analysis
In petrochemical special inspection enterprises, usually due to production needs, there are many pipelines, such as steam, hot water and various industrial solutions, which are usually covered with various insulation materials to ensure the requirements of energy conservation. However, because these pipelines are usually erected on the upper part of the plant or outdoors without any maintenance measures, with the passage of time, the insulation layer and even its pipe wall may be damaged or thinned. Through the infrared thermal imager, It is very easy to find hot spots, so as to take measures to reduce energy waste and ensure the correct process temperature. At the same time, the damaged state of the insulation layer can be understood, so as to accurately calculate the required human and material resources, so as to greatly shorten the workload and time of maintenance. A large number of chemical reactions are usually involved in production, especially in various reaction furnaces, which are accompanied by a certain temperature, resulting in varying degrees of corrosion, especially in some valves, plate heat exchangers, end cover linings, etc. in the early stage, simple leakage is often invisible to the naked eye. Through the infrared thermal imager, we can judge through subtle temperature changes, so as to avoid damage to the environment and personnel.
There will also be many kinds of liquid storage equipment in the factory, which will generally control the materials through a liquid level sensor. Sometimes the liquid level sensor will fail, which will often lead to overflow or cut-off, resulting in production interruption and stagnation. This can also be detected by the infrared thermal imager. Because the materials and these storage devices are different materials, their thermal capacity is different. The liquid level can be clearly reflected on the infrared thermal image. Sometimes, this is also a simple method to detect the liquid level, avoiding many potential dangers.
For the leakage of liquefied natural gas, liquefied petroleum gas and liquefied ethylene, it is colorless and tasteless, and it often needs special instruments to detect it. If it cannot be handled in time, fire, explosion and other accidents may occur. However, using gas sensors to detect gas can only detect at fixed points, while thermal imagers can detect a large area, This is to detect the leakage of gas according to the change of ambient temperature generated in the outside world when the gas is discharged. When the liquefied gas flows out, there is an abnormal temperature around. The location and scale of the gas leakage can be determined by observing with a thermal imager.
Petrochemical enterprises have so many equipment, especially most of them are often under the harsh working conditions of high temperature, high pressure, corrosion and oxidation, with the characteristics of long working cycle and short maintenance time. Especially, once they are in operation, they will be uninterrupted for a long time. Usually, they need to grasp the operating status of all these equipment at the same time, so that they can work out a maintenance plan according to the actual situation. Using infrared thermography technology can clearly Visually and comprehensively discover the damage of the tested object, and a relatively obvious temperature abnormal area will often be formed where there is damage.
Through the infrared thermal imager equipment, we can clearly understand the distribution, size and specific situation of hot spots, and even understand the cause and severity of the problem according to the past status files of these equipment, and take timely actions to maximize the service life of the equipment. This is a dynamic maintenance process, which can formulate the most economical maintenance schedule according to the different use conditions of the equipment. On the other hand, the infrared thermal image can comprehensively reflect the temperature distribution of the tested area, find out the weak links of insulation, and comprehensively and quantitatively evaluate the insulation performance of the tested object. The insulation of all parts of the pipeline can be visually displayed through the infrared thermal image.
