Thread Content
Overview: Chemical enterprises are responsible for eliminating toxic, hazardous, flammable, and explosive chemical substances. Accidents can occur during production, use, transportation, and storage due to poor management in any of these stages. In chemical plants, there are many tanks whose levels need to be measured. From the perspective of safety and measurement accuracy, as science and technology advance, the requirements regarding safety become higher and so do the demands for measurement precision. Traditional contact-based measurement techniques can no longer meet such high standards; therefore, more advanced measurement technologies must be employed in these industries. Current status of tank level measurement in chemical plants: In chemical plants, many materials and products are either toxic, hazardous substances or flammable and explosive hazards. In traditional level measurement, differential pressure transmitters or magnetic flap level gauges are commonly used. These measurement techniques often involve direct contact with the material, making maintenance difficult; they also offer low measurement accuracy and a high failure rate. To achieve safe and accurate level measurement, radar level gauges are the preferred choice. Working principle of radar level gauges: Radar level gauges can be classified into pulse radar and frequency-modulated continuous wave radar based on the method of signal transmission. Pulse radar primarily determines distance by the time difference between signal transmission and reception ； Frequency-modulated continuous-wave radar determines distance by varying the frequency of the transmitted and received signals. This article introduces the use of pulse radar for level measurement. Principle of pulse radar operation: The radar level gauge operates in a transmit-reflect-receive mode. The antenna of the radar level gauge emits electromagnetic waves, which are reflected by the surface of the object being measured before being received by the antenna. The time it takes for these electromagnetic waves to travel from emission to reception is proportional to the distance to the liquid surface. The formula is as follows: D = CT/2, where D represents the distance from the radar level gauge to the liquid surface, C represents the speed of light, and T represents the time it takes for the electromagnetic waves to travel. By recording the time taken by the pulse waves, and since the speed of propagation of the electromagnetic waves is constant, it is possible to calculate the distance from the liquid surface to the radar antenna, thereby determining the liquid level. Schematic diagram of the measurement principle. Measurement features: 1. Radar waves travel at the speed of light (300,000 KM/S); the time difference in the propagation of these radar waves is converted into a level signal, ensuring accurate and stable measurements. 2. Unaffected by temperature and pressure: The operation of radar waves is hardly influenced by environmental temperature and pressure, so radar level gauges are suitable for complex process conditions. 3. It is not affected by the properties of the medium under test; changing the composition of the medium or replacing the entire medium does not impact the measurement results, and no re-calibration is required. 4. Service and maintenance are simple; thanks to contactless measurement, the radar is easy to service and maintain. 5. Radar level gauges can perform measurements in both vacuum and pressurized conditions, and they are accurate, safe, and highly reliable. It can be used without any restrictions and is suitable for various occasions. The convenient use of radar in level measurement in chemical plants: In chemical plants, radar level gauges are used on a very wide scale. Radar has been successfully used for level measurement in the following medium tanks, with excellent results. Liquid ammonia, liquid chlorine, vinyl chloride, ethylene, benzene, phenol, xylene, propane; liquefied gases, naphtha, crude oil, gasoline, diesel, methanol, hydrochloric acid, sulfuric acid, nitric acid, alkaline solutions, ethanol, ethylene glycol, kerosene, formic acid, acetic acid, formaldehyde, hydrofluoric acid, hydrogen fluoride, methane, chloromethane, ethylene oxide, propylene oxide, trichloroethylene, hydrogen sulfide. Application example: The use of radar level gauges in liquid chlorine storage tanks. Liquid chlorine tanks are generally at low temperatures, around minus 20 degrees Celsius. Chlorine is highly corrosive when it comes into contact with water at room temperature; under such conditions, higher requirements are placed on instruments. In traditional liquid chlorine tanks, magnetic flap level gauges are generally used for measurement. The working principle of this measurement method is that a magnetic float is installed in a bypass pipe, and a row of dual-colored magnetic flaps is placed outside the bypass pipe ； The rise or fall of the float causes the magnetic flip rod to rotate 180°. The advantage of this measurement method is that the liquid level is easily visible; however, its disadvantages are also quite obvious: the measurement accuracy is low, there are many safety hazards associated with the installation interfaces, and both installation and maintenance are rather complicated. A radar level gauge is used to measure the liquid chlorine level; it is easy to install and offers high measurement accuracy, capable of reaching millimeter-level precision. It provides valuable guidance for safety monitoring and production processes. Conclusion Level measurement is needed in many areas of modern factory production, especially on chemical production lines, and a good level gauge is an essential instrument on such lines. Radar level gauges are among the types of level gauges with relatively superior performance. Compared to other level gauges, radar measurement is more accurate, they offer greater safety, are easier to install. More importantly, in harsh operating conditions, radar gauges can help extend the normal operation time of a process through precise measurements, and they do not come into direct contact with the medium being measured. Radar level gauges are a very practical type of level measurement instrument in chemical production.