In the industrial production process, the boiler plays an irreplaceable and critical role. It operates at extreme temperatures and pressures to produce steam efficiently, providing the necessary power support for various industrial production processes. Whether it's process heating in manufacturing or energy conversion in power generation, the steam generated by boilers is a central element in keeping production running smoothly. Because of this, to ensure the safe and efficient operation of the boiler has become the basis for stable industrial production.
Thermal shock refers to a series of dangerous conditions caused by sudden temperature changes during boiler operation. When cold water suddenly enters the boiler in a high temperature state, the metal parts inside the boiler will undergo the process of contraction and expansion rapidly due to the rapid change of temperature. This instantaneous physical change will greatly weaken the structural strength of the boiler components. In the long run, repeated thermal stress, boiler parts are very easy to cracks, leaks and other problems, and may even cause catastrophic explosions, a serious threat to the safety of production facilities and the lives and health of people.
In general, the material will rise and fall with the temperature contraction or expansion phenomenon. For such materials as metal with good thermal conductivity, in the rapid change of temperature, the size of the physical changes to a certain extent more uniform. However, if the material has a high degree of tensile strength, then thermal shock may not occur as readily in the face of temperature changes. This is because the material can rely on its own characteristics, buffer the impact of temperature changes in the stress, to maintain the relative stability of the structure.
In the actual operation of the boiler scene, the most typical case of thermal shock is the sudden entry of cold water into the high-temperature boiler. At this time, the metal parts that were originally in a high temperature state, such as the heated surface piping, etc., will be due to the influx of cold water, and the local temperature will instantly drop dramatically. Metal materials in this rapid temperature change, rapid contraction, while the surrounding part is still in the high temperature is maintained in the expansion state. This uneven contraction and expansion creates strong stresses within the metal part. Over time, if such conditions are repeated and the stresses accumulate, tiny cracks will gradually form on the surface or inside the component. These cracks will continue to expand with the occurrence of each thermal shock, which may eventually lead to component leakage, or even complete damage, seriously affecting the normal operation of the boiler and safety performance.
In industrial production, there are sometimes such a situation: the water from the boiler outflow, not yet fully cooled back into the boiler. This uncooled water enters the boiler and mixes with the hot water that is boiling inside the furnace. This mixing process produces a dual effect of cooling and reheating on the surface of the boiler piping. The pipe surfaces undergo rapid cycles of expansion and contraction due to rapid alternating temperature changes. Over time, the structural strength of the piping can be severely compromised, greatly increasing the risk of thermal shock occurring. For example, in some chemical production plants, such problems occur frequently due to poorly designed water circulation systems, resulting in frequent repair and replacement of boiler piping.
When the boiler size selected by the enterprise is too large and exceeds the actual production demand, it is also easy to cause thermal shock problems. Too large a boiler will produce excessive steam, in the production of low load, steam condensation formed by the cooling water flow back to the boiler, will be mixed with the high temperature of the furnace water. This mixing will not only destroy the original stable temperature field inside the boiler, but also make the metal parts to withstand drastic temperature changes, resulting in serious thermal shock damage. Moreover, once the thermal shock caused by the boiler failure, the destructive force will be more serious due to the boiler volume, posing a great threat to the life and safety of the surrounding operators.
Sudden rise or fall in ambient temperature, the boiler operation also has a non-negligible impact. This is just like the human body in a short period of time encountered extreme temperature changes, there may be heat stroke (pyrexia) or hypothermia and other life-threatening conditions. Boilers can be subjected to rapid changes in ambient temperature, which can also disturb the temperature distribution of exposed external components as well as the internal temperature. For example, on a cold winter day when the outdoor temperature drops suddenly and the boiler is in operation, the temperature of the boiler's exterior walls will drop rapidly while the interior remains hot. This sharp change in the temperature difference between the inside and outside will lead to uneven contraction and expansion of the boiler metal material, thus triggering thermal stress and increasing the possibility of thermal shock.
Materials such as rocks, glass and ceramics, due to their poor thermal conductivity, are very susceptible to thermal shock when the temperature changes. Rock, for example, when it is close to the heat source (such as campfire), the surface temperature will rise rapidly, while the internal temperature due to the slow conduction of heat, warming lag. At this time, if suddenly splashed with cold water, the surface temperature of the rock drops sharply and shrinks, while the internal temperature is still relatively high and expansion of the state. This uneven contraction and expansion will cause strong stresses inside the rock, eventually leading to rock rupture. In boiler components where similar materials with poor thermal conductivity are used, there is a similar risk of thermal shock in the event of rapid temperature changes during operation.
In the manufacture of boilers, some components may be made of relatively poor materials due to factors such as design or cost. These materials are not able to disperse and withstand thermal stresses as effectively as high quality materials when faced with rapid temperature fluctuations. For example, some low-quality boiler piping materials are prone to fatigue damage under the effect of long-term hot and cold alternation, resulting in tiny cracks on the surface of the pipeline, which in turn triggers thermal shock and affects the normal operation of the boiler.
In the pursuit of energy saving and emission reduction in the enterprise, sometimes there will be human error resulting in increased risk of thermal shock. For example, technicians of the energy management system may adjust system control parameters in order to save fuel costs and optimize boiler operating performance. One common means of saving energy is to reduce the return water temperature. However, if the technician makes adjustments without due consideration of the boiler manufacturer's recommendations and sets the return water temperature too low, a large amount of low-temperature water can enter the boiler quickly and mix with the high-temperature furnace water, which can trigger drastic temperature changes and lead to thermal shock. Although the energy management team's intentions were good, this misstep posed a significant safety risk to the boiler's operation.
The plant operator has a great legal responsibility to ensure that the boiler is properly maintained and safely operated. As a high-pressure equipment, the operation of the boiler is directly related to the safety of the production plant and the life and health of the employees. From a legal point of view, the operator must carry out regular maintenance of the boiler in strict accordance with the relevant standards and norms to ensure that all safety devices and control systems are functioning properly. This is not only responsible for the enterprise's own production, but also to comply with the basic requirements of laws and regulations.
In the event of an explosion or structural failure caused by a poorly maintained or improperly operated boiler, the plant operator may be held legally liable, including compensation for injuries and property damage caused by the accident. In legal proceedings, if it can be proved that the accident was caused by the operator's failure to fulfill its obligations of maintenance and safe operation, the operator will face severe legal sanctions.
If the operator fails to provide proper boiler operation training to its employees or fails to strictly enforce the safety rules and regulations, resulting in thermal shock accidents caused by the lack of necessary knowledge or non-compliance of the employees in the course of operation, the operator will be held responsible. For example, if an employee, without understanding the boiler operating procedures, mistakenly injects a large amount of cold water into a high temperature boiler at a rapid rate, causing a thermal shock that results in an explosion, the operator will be liable for the legal consequences of poor training and management.
Maintenance contractors are also liable for ignoring early signs of fatigue in boiler metal parts during boiler maintenance, or failing to carry out comprehensive inspections in accordance with prescribed inspection procedures and standards, and failing to detect potential safety hazards in a timely manner, which ultimately leads to boiler failures caused by thermal shocks. For example, if maintenance personnel fail to detect tiny cracks in boiler piping due to prolonged thermal stress during regular inspections, and the cracks eventually widen to cause leakage and explosion, the maintenance contractor will be held liable for dereliction of duty.
The boiler manufacturer will be held liable if, upon investigation, it is found that the boiler is susceptible to thermal shock and causes failure due to design defects. For example, if the water circulation system of a boiler is not properly designed so that cold water tends to accumulate quickly in a localized area, triggering a thermal shock, the manufacturer will be held liable for the consequences of an accident caused by the design problem, and may be required to recall the faulty product and compensate the victims.
The cycling of a burner usually refers to its frequent opening and closing, also known as “short cycle operation”. When a burner is short-cycled, the temperature inside the boiler will fluctuate frequently and dramatically over a short period of time. Such frequent temperature changes will cause the metal parts of the boiler to be repeatedly subjected to thermal stresses, which in the long run will easily lead to metal fatigue and increase the probability of thermal shock occurring. For example, in some small factories, due to improper burner control, the burner frequently starts and shuts down quickly, resulting in faster damage to boiler components and a significant increase in maintenance costs.
In order to reduce the frequency of burner cycling, you can choose to install burners with high modulation ratios. This type of burner is able to maintain a low combustion rate for a long period of time, which reduces the dramatic fluctuations in the internal temperature of the boiler compared to frequent short-term operation at a high combustion rate. At the same time, the correct commissioning of the burner is also essential. Through accurate commissioning, problems in the control system can be found in a timely manner to ensure that the burner adjustment ratio meets the actual operational requirements of the boiler, thereby reducing the risk of thermal shock.
If the selected boiler size is too large, exceeding the steam load required for actual production, it is easy to run a short cycle. This is because in actual production, the load often cannot adequately match the excessively large boiler power, resulting in frequent startup and shutdown of the boiler, thus increasing the possibility of thermal shock. On the contrary, if the boiler size is too small, it will not be able to meet the demand for the amount of steam in the production process, which will affect the production efficiency. For example, a factory in the expansion plan canceled, but still continue to use the original expansion in accordance with the needs of the configuration of the oversized boiler, the result not only increased energy consumption, but also frequent thermal shock problems, resulting in frequent equipment failure.
Accurately calculating the amount of steam needed according to actual production demand and selecting the right size boiler accordingly is a key step in ensuring stable boiler operation and preventing thermal shock. Reasonable boiler sizing not only ensures that the boiler operates at high efficiency to meet the production demand for steam, but also avoids various problems caused by improper sizing and reduces the risk of equipment damage and operating costs.
The formation of scale inside the boiler will have a significant impact on the occurrence of thermal shock. Scale has insulating properties and it adheres to the heated surfaces of the boiler, preventing the normal transfer of heat. This causes the temperature distribution of the boiler's metal parts to become uneven as they are heated. For example, in the thicker parts of the scale, the heat is difficult to conduct out, and the metal temperature will be abnormally high; while in the parts with less scale or no scale, the temperature is relatively low. This uneven temperature distribution will subject the metal parts to additional thermal stress and increase the risk of thermal shock.
To prevent scale-induced thermal shock problems, existing scale can be removed chemically and measures taken to prevent new scale from forming. Regular cleaning of the boiler with a suitable descaling agent can effectively remove the scale on the heating surface. At the same time, in the course of boiler operation, the chemical composition of the boiler water is adjusted by adding water quality stabilizers and other means to inhibit the generation of scale. This will ensure that the temperature distribution of the boiler metal parts is uniform, reducing the possibility of thermal shock.
When a large amount of cold water is returned directly to the boiler, it can cause a sharp drop in the internal temperature of the boiler in an instant, triggering a severe thermal shock. This drastic change in temperature puts great stress on the metal parts of the boiler, which may lead to deformation, cracking or even damage to the parts. For example, in some heating systems, if there is no reasonable control of the return water temperature, a large number of low-temperature return water directly into the hot water boiler, it is easy to trigger thermal shock, damage to the boiler equipment.
Adopting the “Dual Loop System” is an effective solution. The system consists of a loop that handles low-temperature return water and a high-temperature loop. The two circuits are connected by installing valves that allow the cold water in the low-temperature return water to mix with the hot water in the high-temperature circuit. In this way, the temperature of the cold water is raised before it enters the boiler, thus avoiding sharp temperature changes caused by cold water entering the boiler directly and effectively reducing the risk of thermal shock. This system can flexibly adjust the return water temperature according to actual demand, to ensure the safe and stable operation of the boiler.
Bidragon boiler adopts a carefully optimized structural design, such as the use of water tube boilers or other hybrid boiler structure. This design effectively spreads out temperature shocks and reduces the impact of localized temperature differences on boiler components. In a water tube boiler, water circulates more smoothly, resulting in a more even temperature distribution on the heated surface. Compared with the traditional boiler structure, the water tube boiler can better cope with temperature changes, reduce the accumulation of stress due to uneven heating and cooling, thus significantly improving the stability of boiler operation.
The unique water circulation design of the Bidragon water tube boiler ensures that water flows quickly and evenly within the boiler. This smooth water circulation allows heat to be transferred more efficiently, avoiding the occurrence of localized overheating or overcooling. In actual operation, the uniform temperature distribution can reduce the thermal stress of metal parts due to temperature differences, improve the service life of the parts, and reduce the risk of damage to the boiler from thermal shock.
Bidragon boilers are made of high-quality boiler-specific steel, which has excellent resistance to high temperatures and wear. In the process of long-term exposure to high temperature loads and frequent temperature changes, but still maintain stable physical and mechanical properties. For example, the selected steel can maintain good strength and toughness under high temperature environment, and will not be easily deformed or embrittled due to temperature rise and fall, which provides a solid foundation for the safe and stable operation of the boiler.
In addition to high-quality steel, Bidragon boilers are equipped with a series of high-temperature resistant accessories. These fittings also have excellent thermal fatigue resistance and are able to operate under severe temperature conditions. During boiler operation, even in the face of frequent temperature fluctuations, these fittings are able to maintain structural integrity and work in concert with the boiler body, effectively extending the service life of the entire boiler system and reducing maintenance costs.
The Bidragon boiler is equipped with an advanced temperature control system, which is capable of real-time and accurate monitoring of the boiler's inlet water temperature and flow rate. Through high-precision sensors, the system is able to quickly capture any slight changes in temperature and flow rate and transmit the data to the control center in a timely manner. This real-time monitoring function provides an accurate data basis for the subsequent intelligent regulation.
Based on the real-time monitoring data, the temperature control system of Bidragon boiler is capable of intelligent adjustment. When the system detects that a large amount of cold water may be entering the boiler and there is a risk of triggering a sharp change in temperature, it will automatically take appropriate measures. For example, by adjusting the opening of the inlet valve to control the rate of entry of cold water, or adjusting the power of the burner to increase the temperature inside the furnace to maintain the internal temperature of the boiler at a stable level. This intelligent adjustment mechanism effectively avoids thermal shocks caused by rapid temperature changes and improves the overall operating efficiency and safety of the boiler.
Summary of the causes of thermal shock and preventive measures
Through an in-depth discussion of the boiler thermal shock problem, we have clarified that its main causes cover water cycle abnormalities, sudden changes in ambient temperature, material properties and human error and other aspects. To varying degrees, these factors affect the temperature distribution and material stress state inside the boiler, triggering the thermal shock phenomenon, posing a serious threat to the safe operation of the boiler.
At the same time, we also elaborate a series of effective preventive measures, including reducing the frequency of burner cycling, rationally selecting boiler dimensions, appropriately dealing with scale, and preventing the direct return of cold water. These measures provide a comprehensive solution to reduce the risk of thermal shock from a variety of perspectives, including operation management, equipment selection and maintenance.
Importance of selecting a reliable boiler
In the case of the Bidragon boiler, we have seen how the advantages of advanced design, high-quality materials and precise temperature control can be effective in avoiding thermal shock. the Bidragon boiler is able to effectively meet the challenge of thermal shock and ensure the safe and stable operation of the boiler by optimizing the structural design, selecting durable materials and equipping it with an intelligent temperature control system. This not only reduces maintenance costs and accident rates, but also ensures the continuity and reliability of production.
For industrial enterprises, when choosing boiler equipment, they should give full consideration to thermal shock and other safety factors, and prioritize reliable products with good resistance to thermal shock like Bureau Veritas. Only in this way can we guarantee production safety while realizing the goal of efficient, energy-saving production and promoting sustainable development of enterprises.
