Automatic material circulating heating device

Abstract

The utility model discloses a kind of automatic material circulation heating devices, including independent heating unit, thermostatic circulation pipeline and control unit, independent heating unit includes electric heater, circulating pump and expansion water tank. Thermostatic circulation pipeline includes coil pipe and connecting pipeline, coil pipe is set around the outer wall of ripening tank, the import and export of coil pipe are connected with the export and import of independent heating unit by connecting pipeline, constitute a closed circulation loop. Control unit includes PLC controller, temperature sensor and electrical control cabinet, temperature sensor is set in ripening tank or thermostatic circulation pipeline system, for detecting temperature signal;PLC controller receives the signal of temperature sensor, and exports control instruction to electrical control cabinet, and the start-stop and power of electric heater and circulating pump are controlled by electrical control cabinet. Wherein, independent heating unit provides thermostatic circulation pipeline system to coil pipe with thermostatic heat medium, to automatically, uniformly heat the material in ripening tank.

Description

Technical Field

[0001] This utility model relates to the field of material curing technology, and in particular to an automatic circulating heating device for materials. Background Technology

[0002] In material handling processes in industries such as chemicals, food, and pharmaceuticals, material maturation is a crucial step. Maturation typically requires continuous heating at a specific temperature for a certain period to ensure the materials reach the desired reaction or mixing state. Currently, common heating methods for maturation tanks often employ centralized heating systems, where a central heat source (such as a boiler) simultaneously supplies hot water or steam to multiple workshops or equipment via a pipeline network. This method lacks effective temperature control, resulting in significant temperature fluctuations and an inability to provide a stable heating environment for the materials. In chemical production, unstable heating temperatures can lead to unstable chemical reactions, inconsistent product quality, and even potential side reactions that generate harmful substances. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an automatic material circulation heating device, which can realize automatic and uniform heating of materials in a curing tank, has stable temperature control capability, simple structure, convenient operation, and low energy consumption.

[0004] An automatic material circulation heating device according to a first aspect of this utility model includes an independent heating unit, a constant-temperature circulation pipeline, and a control unit. The independent heating unit includes an electric heater, a circulation pump, and an expansion tank. The constant-temperature circulation pipeline includes a coil and connecting pipes. The coil is arranged around the outer wall of the curing tank. The inlet and outlet of the coil are connected to the outlet and inlet of the independent heating unit through the connecting pipes, forming a closed circulation loop. The control unit includes a PLC controller, a temperature sensor, and an electrical control cabinet. The temperature sensor is installed inside the curing tank or on the constant-temperature circulation pipeline system to detect temperature signals. The PLC controller receives the signals from the temperature sensor and outputs control commands to the electrical control cabinet, which controls the start / stop and power of the electric heater and the circulation pump. The independent heating unit provides a constant-temperature heat medium to the coil through the constant-temperature circulation pipeline system to automatically and uniformly heat the material in the curing tank.

[0005] The automatic material circulation heating device according to the embodiments of this utility model has at least the following beneficial effects: A heat medium is provided by an independent heating unit, and the heat is uniformly transferred to the material through a coil of a constant-temperature circulation pipeline surrounding the outer wall of the curing tank, avoiding local overheating or undercooling. This achieves automatic and uniform heating of the material, ensuring stable material quality and performance. The temperature sensor in the control unit monitors the temperature in real time, and the PLC controller precisely controls the electric heater and circulation pump based on the temperature signal. This allows for rapid response to temperature changes, stabilizing the temperature within the set range and providing a stable heating environment for the material, which is beneficial for improving product qualification rate and consistency. Furthermore, the overall structure of this device is relatively simple, with reasonable connections and layouts between components, making it easy to install and maintain. Operators only need to set the parameters of the PLC controller to achieve automated control of the heating process, eliminating the need for frequent on-site monitoring and adjustments by professional personnel, thus reducing labor costs and operational difficulty. Moreover, due to the ability to achieve precise temperature control and heat medium circulation, heat loss and energy waste are reduced, resulting in lower energy consumption compared to traditional heating devices, meeting the environmental protection requirements of energy conservation and emission reduction.

[0006] According to some embodiments of the present invention, the independent heating unit further includes a temperature regulating valve and a pressure gauge. The temperature regulating valve is used to precisely regulate the temperature of the output heat medium, and the pressure gauge is used to monitor the pressure of the circulation pipeline system.

[0007] According to some embodiments of the present invention, the constant temperature circulation pipeline system further includes a heat insulation layer, which covers the outer surface of the coil and the connecting pipe.

[0008] According to some embodiments of the present invention, the coil is a stainless steel metal tube, which is tightly attached to the outer wall surface of the curing tank in the form of spiral winding or jacket.

[0009] According to some embodiments of the present invention, the control unit further includes a human-machine interface, which is connected to the PLC controller and is used to set and display heating temperature and heating time parameters.

[0010] According to some embodiments of this utility model, the PLC controller has a built-in PID control algorithm, which dynamically adjusts the heating power of the electric heater based on the deviation between the signal fed back by the temperature sensor and the set value, so that the temperature of the material in the curing tank is maintained within the set range.

[0011] According to some embodiments of this utility model, the control unit is also connected to a liquid level sensor and an alarm. The liquid level sensor is installed in the expansion tank to monitor the liquid level. When the liquid level is lower or higher than a set threshold, the PLC controller triggers the alarm.

[0012] According to some embodiments of this utility model, the heat transfer medium is water or heat transfer oil.

[0013] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0015] Figure 1 This is a schematic diagram of an automatic material circulation heating device according to an embodiment of the present invention.

[0016] Reference numerals: 100 for curing tank; 200 for constant temperature circulation pipeline; 210 for coil; 220 for connecting pipe; 300 for independent heating unit; 310 for electric heater; 320 for circulation pump; 330 for expansion tank; 340 for temperature regulating valve; 350 for pressure gauge; 400 for control unit; 410 for temperature sensor; 420 for electrical control cabinet; 430 for human-machine interface; 440 for liquid level sensor. Detailed Implementation

[0017] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0018] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0019] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0020] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of these terms in this utility model based on the specific content of the technical solution. In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In the description of this specification, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0021] Reference Figure 1 This utility model proposes an automatic material circulation heating device, including an independent heating unit 300, a constant temperature circulation pipeline 200 and a control unit 400.

[0022] Specifically, the independent heating unit 300 includes an electric heater 310, a circulation pump 320, and an expansion tank 330. The electric heater 310 heats the heat transfer medium to the required temperature. The circulation pump 320 provides power to allow the heat transfer medium to flow throughout the circulation system. The expansion tank 330 accommodates the volume change of the heat transfer medium due to temperature increase, ensuring stable system pressure.

[0023] The constant-temperature circulation pipeline 200 includes a coil 210 and connecting pipes 220. The coil 210 is arranged around the outer wall of the curing tank 100. This design allows the heat medium to be evenly transferred to the material inside the curing tank 100 through heat conduction when flowing through the coil 210. The inlet and outlet of the coil 210 are connected to the inlet and outlet of the independent heating unit 300 through the connecting pipes 220, forming a closed circulation loop. Under the action of the circulation pump 320, the heat medium flows out from the independent heating unit 300, releases heat through the coil 210, and then returns to the independent heating unit 300 for reheating. This cycle repeats continuously, providing heat to the material.

[0024] The control unit 400 includes a PLC controller, a temperature sensor 410, and an electrical control cabinet. The temperature sensor 410 is located inside the curing tank 100 or on the constant temperature circulation pipeline 200 system. Its function is to detect temperature signals in real time and accurately transmit these signals to the PLC controller. As the core of the entire control system, the PLC controller receives the signals from the temperature sensor 410, analyzes and processes them according to preset temperature parameters, and then outputs control commands to the electrical control cabinet. Based on the received commands, the electrical control cabinet precisely controls the start / stop and power of the electric heater 310 and the circulation pump 320. When the temperature is lower than the set value, the PLC controller instructs the electrical control cabinet to start the electric heater 310 and adjust it to an appropriate power for heating, while simultaneously starting the circulation pump 320 to circulate the heat medium. When the temperature reaches the set value, the PLC controller instructs the electrical control cabinet to reduce the power of the electric heater 310 or stop heating to maintain a stable temperature. Specifically, the independent heating unit 300 provides a constant-temperature heat medium to the coil 210 through the constant-temperature circulation pipeline 200 system, thereby realizing automatic and uniform heating of the material in the curing tank 100.

[0025] Understandably, the heat medium is provided by the independent heating unit 300 and flows around the outer wall of the curing tank 100 via the coil 210 of the constant temperature circulation pipeline 200. This ensures that the heat medium is evenly transferred to the material, avoiding local overheating or undercooling, and achieving automatic and uniform heating of the material, thus guaranteeing the stability of the material's quality and performance. The temperature sensor 410 in the control unit 400 monitors the temperature in real time, and the PLC controller precisely controls the electric heater 310 and the circulation pump 320 based on the temperature signal. This allows for rapid response to temperature changes, stabilizing the temperature within the set range and providing a stable heating environment for the material, which is beneficial for improving the product's pass rate and consistency. In addition, the overall structure of this device is relatively simple, with reasonable connections and layouts between components, making it easy to install and maintain. Operators only need to set the parameters of the PLC controller to achieve automated control of the heating process, eliminating the need for frequent on-site monitoring and adjustments by professional personnel, thus reducing labor costs and operational difficulty. Furthermore, due to the ability to achieve precise temperature control and heat medium recycling, heat loss and energy waste are reduced, resulting in lower energy consumption compared to traditional heating devices, meeting the environmental protection requirements of energy conservation and emission reduction.

[0026] In some embodiments, a certain sauce needs to be heated and matured in a food processing plant. The automatic material circulation heating device of this invention is used. The maturation tank 100 is made of stainless steel and has a volume of 500L. In the independent heating unit 300, the electric heater 310 uses a 15kW electric heating element, capable of quickly heating the heat medium (heat transfer oil) to the required 80°C. The circulation pump 320 uses a centrifugal pump with a flow rate of 5m³ / h and a head of 10m to ensure sufficient dynamic flow of the heat medium in the circulation system. The volume of the expansion tank 330 is calculated based on the expansion coefficient and temperature change range of the heat medium and is 50L. In the constant temperature circulation pipeline 200, the coil 210 uses a 25mm diameter stainless steel tube, wrapped around the outer wall of the maturation tank 100 for a total of 5 turns to ensure sufficient heat exchange area. The connecting pipe 220 uses a seamless steel pipe with the same diameter as the coil 210 and is insulated to reduce heat loss. In the control unit 400, the temperature sensor 410 is a platinum resistance temperature sensor with an accuracy of ±0.5℃, which is installed inside the curing tank 100 and at the inlet and outlet of the coil 210 to monitor the temperature at different locations in real time. The PLC controller is a small PLC from a well-known brand, which has powerful data processing and control capabilities. The electrical control cabinet precisely controls the start-up, shutdown, and power of the electric heater 310 and the circulating pump 320 according to the instructions of the PLC controller.

[0027] During operation, the heating temperature is first set to 80℃ in the PLC controller. After starting the device, the electric heater 310 begins heating the heat transfer oil. The circulating pump 320 delivers the heated heat transfer oil to the coil 210, through which heat is transferred to the sauce in the maturation tank 100. The temperature sensor 410 monitors the temperature in real time. When the temperature approaches the set value, the PLC controller automatically adjusts the power of the electric heater 310 to stabilize the temperature at 80℃. After a period of heating and maturation, the sauce reaches the required quality.

[0028] In other embodiments, for chemical production, a certain chemical solution needs to be heated for a reaction. The curing tank 100 is made of glass-lined material with a volume of 1000L to prevent corrosion of the tank by the chemical solution. In the independent heating unit 300, the electric heater 310 uses a 20kW electromagnetic heater, characterized by fast heating speed and high efficiency. The circulation pump 320 is a magnetic pump with a flow rate of 8m³ / h and a head of 12m to ensure no leakage of the heat medium (steam condensate) during circulation. The expansion tank 330 has a volume of 80L. The coil 210 of the constant temperature circulation pipeline 200 uses a 32mm diameter titanium tube, encircling the outer wall of the curing tank 100 six times. Titanium tubes have good corrosion resistance and are suitable for chemical environments. The connecting pipes 220 also use titanium tubes and undergo strict insulation and anti-corrosion treatment. In the control unit 400, the temperature sensor 410 is a thermocouple temperature sensor with an accuracy of ±1℃, installed in key positions inside the curing tank 100 and in the constant temperature circulation pipeline 200. A medium-sized PLC controller is used, featuring more input / output interfaces and more powerful control functions. The electrical control cabinet precisely controls the operation of the electric heater 310 and the circulation pump 320 according to the instructions of the PLC controller. During production, the heating temperature is set to 60℃. After the device is started, the electromagnetic heater quickly heats the steam condensate to the set temperature, and the circulation pump 320 delivers the heat medium to the coil 210, providing uniform heat to the chemical solution. The temperature sensor 410 provides real-time temperature feedback, and the PLC controller adjusts the power of the electric heater 310 in a timely manner according to temperature changes, ensuring the reaction proceeds under stable temperature conditions, thus improving the efficiency of the chemical reaction and product quality.

[0029] Reference Figure 1 Furthermore, the independent heating unit 300 is additionally equipped with a temperature regulating valve 340 and a pressure gauge 350. The temperature regulating valve 340 is a high-precision electric three-way regulating valve, installed on the heat medium output pipeline between the electric heater 310 and the circulating pump 320. This regulating valve, by receiving control signals from the PLC controller, can precisely adjust the flow rate of the heat medium entering the circulation pipeline according to preset temperature parameters, thereby achieving precise control of the output heat medium temperature. For example, when the output heat medium temperature is detected to be higher than the set value, the PLC controller issues a command to reduce the opening of the regulating valve, reducing the flow rate of the high-temperature heat medium while increasing the flow rate of the bypass low-temperature heat medium to achieve cooling; conversely, it increases the flow rate of the high-temperature heat medium. The pressure gauge 350 is a high-temperature resistant, high-precision digital pressure gauge, installed at a key location in the constant-temperature circulation pipeline 200 system, such as at the outlet of the circulating pump 320. The pressure gauge 350 monitors the pressure of the circulation pipeline system in real time and transmits the pressure signal to the PLC controller. The PLC controller analyzes and processes the pressure signal. When the pressure exceeds the normal range, it can take corresponding protective measures, such as stopping the operation of the circulating pump 320 or adjusting the system parameters.

[0030] The addition of temperature regulating valve 340 enables the independent heating unit 300 to precisely adjust the temperature of the output heat medium according to actual needs, greatly improving the temperature control accuracy of the heating device. This better meets the stringent heating temperature requirements of different materials, ensuring the quality and stability of material heating. The pressure gauge 350 allows for real-time monitoring of the circulation pipeline system pressure. When abnormal pressure occurs, it promptly sends a signal, facilitating operator intervention and preventing damage to the equipment due to excessively high or low pressure, thus improving the safety and reliability of the device operation.

[0031] In some embodiments, an insulation layer is added to the constant temperature circulation pipeline 200 system. The insulation layer uses high-quality polyurethane foam material, which has excellent insulation performance and corrosion resistance. After the coils 210 and connecting pipes 220 are installed, the polyurethane foam material is evenly wrapped around the outer surface of the coils 210 and connecting pipes 220. The wrapping thickness is determined according to actual needs and ambient temperature, generally 30-50 mm. To enhance the insulation effect, an aluminum foil reflective film is wrapped around the insulation layer to prevent heat loss through radiation. The insulation layer effectively reduces the heat loss of the heat medium to the outside through the coils 210 and connecting pipes 220 during circulation, improving heat utilization and reducing energy consumption. Simultaneously, it reduces the influence of ambient temperature on the heat medium temperature, allowing the heat medium to maintain the set temperature more stably, thereby ensuring the uniformity and stability of material heating within the curing tank 100, improving heating efficiency, and reducing production costs.

[0032] In some embodiments, the coil 210 is made of stainless steel. A suitable stainless steel tube, such as one with a diameter of 20-32 mm, is selected based on the shape and size of the curing tank 100. If spiral winding is used, the stainless steel tube is wound evenly upwards from the bottom of the curing tank 100, following a specific pitch, to ensure a tight fit between the coil 210 and the outer wall of the curing tank 100, thereby enhancing heat conduction. After winding, a special clamp is used to fix the coil 210 to the outer wall of the curing tank 100 to prevent it from loosening. If a jacketed design is used, a jacket space concentric with the curing tank 100 is machined into the outer wall of the curing tank 100. The stainless steel tube is arranged within the jacket along a specific path, ensuring full contact between the coil 210 and the outer wall of the curing tank 100. The jacket is then sealed by welding or other methods to form a closed heating channel. Stainless steel tubing possesses excellent thermal conductivity, corrosion resistance, and mechanical strength, enabling it to quickly and evenly transfer heat from the heat medium to the material within the curing tank 100, ensuring uniform heating. The spiral winding or jacketed design allows the coil 210 to fit tightly against the outer wall of the curing tank 100, further improving heat transfer efficiency and reducing heat loss. Simultaneously, the use of stainless steel extends the service life of the coil 210, reducing equipment maintenance costs.

[0033] Reference Figure 1 The control unit 400 is equipped with a human-machine interface 430. The human-machine interface 430 uses a touch-screen LCD display, which is connected to the PLC controller via a data cable. The touch-screen LCD display features an intuitive and user-friendly interface, including a heating temperature setting area, a heating time setting area, a temperature display area, a time display area, and various operation buttons.

[0034] Operators can easily set parameters such as heating temperature and heating time by touching the corresponding areas on the screen. For example, in the heating temperature setting area, the desired temperature value can be entered by clicking the number keys; in the heating time setting area, the heating duration of the material can be set. Simultaneously, the PLC controller transmits the real-time collected temperature and time information to the touch-screen LCD display for display, allowing operators to easily monitor the operating status of the heating device.

[0035] It should be noted that the PLC controller incorporates a built-in PID control algorithm. The PID control algorithm is a feedback control algorithm widely used in industrial control. It calculates the control quantity by performing proportional (P), integral (I), and derivative (D) operations on the deviation between the setpoint and the actual feedback value, thereby achieving precise control of the controlled object. The PLC controller with the built-in PID control algorithm can dynamically and precisely adjust the heating power of the electric heater 310 based on the deviation between the signal from the temperature sensor 410 and the setpoint, ensuring that the material temperature in the curing tank 100 remains within the set range, achieving high-precision temperature control. Compared with traditional on / off control methods, the PID control algorithm effectively reduces temperature fluctuations and improves the quality and stability of material heating, making it particularly suitable for material heating processes with strict temperature requirements.

[0036] Reference Figure 1 The control unit 400 connects to the level sensor 440 and the alarm. The level sensor 440 is a high-precision float-type level sensor, installed inside the expansion tank 330. The float moves up and down with changes in the liquid level, and the level signal is converted into an electrical signal and transmitted to the PLC controller via a linkage. The alarm is an audible and visual alarm, installed in a location easily visible to the operator and connected to the PLC controller. The PLC controller has preset level thresholds for the expansion tank 330, including minimum and maximum levels. When the level sensor 440 detects that the liquid level in the expansion tank 330 is below the minimum threshold or above the maximum threshold, it transmits a signal to the PLC controller. The PLC controller immediately triggers the audible and visual alarm, alerting the operator to take timely measures, such as adding or draining excess heat transfer medium.

[0037] It should be noted that the heat transfer medium can be water or heat transfer oil depending on the different material characteristics and heating requirements. Water is chosen as the heat transfer medium when the heating temperature requirement is not high, the cost is low, and the material is not corrosive to water. Water is injected into the water tank of the independent heating unit 300, heated by the electric heater 310, and the circulating pump 320 delivers the heated water to the constant temperature circulation pipeline 200 to provide heat to the material in the curing tank 100.

[0038] When higher heating temperatures are required, high temperature control precision is demanded, or the material is corrosive to water, heat transfer oil is selected as the heat medium. Heat transfer oil possesses excellent thermal stability and heat transfer performance, enabling stable operation at higher temperatures. The heat transfer oil is injected into the storage tank of the independent heating unit 300, heated by an electric heater 310, and then pumped by a circulation pump 320 to the constant-temperature circulation pipeline 200, thus heating the material.

[0039] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. An automatic material circulation heating device, characterized in that, include: Independent heating unit, including electric heater, circulating pump and expansion tank; The constant temperature circulation pipeline includes a coil and connecting pipes. The coil is arranged around the outer wall of the curing tank. The inlet and outlet of the coil are connected to the outlet and inlet of the independent heating unit through the connecting pipes, forming a closed circulation loop. The control unit includes a PLC controller, a temperature sensor, and an electrical control cabinet. The temperature sensor is installed inside the curing tank or on the constant temperature circulation pipeline system to detect temperature signals. The PLC controller receives the signals from the temperature sensor and outputs control commands to the electrical control cabinet, which controls the start / stop and power of the electric heater and the circulation pump. The independent heating unit provides a constant-temperature heat medium to the coil through the constant-temperature circulation pipeline system to automatically and uniformly heat the material in the maturation tank.

2. The automatic material circulation heating device according to claim 1, characterized in that, The independent heating unit also includes a temperature regulating valve and a pressure gauge. The temperature regulating valve is used to precisely regulate the temperature of the output heat medium, and the pressure gauge is used to monitor the pressure of the circulation pipeline system.

3. The automatic material circulation heating device according to claim 1, characterized in that, The constant temperature circulation pipeline system also includes an insulation layer, which covers the outer surface of the coil and connecting pipes.

4. The automatic material circulation heating device according to claim 1, characterized in that, The coil is a stainless steel metal tube that is tightly attached to the outer wall surface of the curing tank in the form of spiral winding or jacket.

5. The automatic material circulation heating device according to claim 1, characterized in that, The control unit also includes a human-machine interface, which is connected to the PLC controller and is used to set and display heating temperature and heating time parameters.

6. The automatic material circulation heating device according to claim 1, characterized in that, The PLC controller has a built-in PID control algorithm. Based on the deviation between the signal fed back by the temperature sensor and the set value, it dynamically adjusts the heating power of the electric heater to maintain the temperature of the material in the maturation tank within the set range.

7. The automatic material circulation heating device according to claim 1, characterized in that, The control unit is also connected to a liquid level sensor and an alarm. The liquid level sensor is installed in the expansion tank to monitor the liquid level. When the liquid level is lower or higher than a set threshold, the PLC controller triggers the alarm.

8. The automatic material circulation heating device according to claim 1, characterized in that, The heat transfer medium is water or heat transfer oil.

Images