Installation and use of external-mounted level gauges in LPG storage tanks

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The last edit of this post was made by Level Gauge R&D on 2017-6-29 at 15:44. I. Prospects for liquefied gas: With the development of the petrochemical industry, liquefied petroleum gas, as a basic raw material in the chemical industry and a new type of fuel, has received increasing attention. In chemical manufacturing, liquefied petroleum gas is a by-product obtained by refineries during the catalytic and thermal cracking of crude oil. The main components of catalytic cracking gas are as follows (%): hydrogen 5–6, methane 10, ethane 3–5, ethylene 3, propane 16–20, propylene 6–11, butane 42–46, butenes 5–6, and hydrocarbons with 5 or more carbon atoms 5–12. It is used to produce synthetic plastics, synthetic rubbers, synthetic fibers, as well as products such as pharmaceuticals, **, and dyes. Using liquefied petroleum gas as fuel, thanks to its high calorific value, absence of smoke and ash, and ease of use, it has become widely adopted in people’s daily lives. In addition, liquefied petroleum gas is also used for cutting metal, baking agricultural products, and firing in industrial furnaces. II. Chemical properties of liquefied gas: A colorless, volatile liquid obtained by pressurizing and cooling refinery gas or natural gas. Flammable. When the concentration of liquefied petroleum gas in the air reaches a certain level, it will explode upon contact with an open flame. Density: The density of liquid liquefied petroleum gas is 580 kg/m3, while its density in gaseous state is 2.35 kg/m3. The relative density of the gas phase is 1.686 (that is, with the density of air set at 1, the density of liquid liquefied petroleum gas relative to air is 1.686). III. Monitoring of Liquefied Petroleum Gas Level: Liquefied petroleum gas level meters utilize advanced digital signal processing technology, which eliminates the influence of the container wall thickness and enables true non-contact measurement of the liquid level inside sealed containers from outside the container. The sonar sensor (probe) is installed directly below the outer wall (bottom) of the container to be tested; no holes need to be made in the container, making installation simple. It enables online installation and debugging without disrupting production. It enables accurate measurement of the liquid level of various hazardous substances such as flammable, explosive, and toxic materials, strong acids, strong bases, as well as various pure liquids, within sealed containers under high temperature and pressure conditions. When a liquefied gas level gauge measures the liquid level, sonar wave signals are sent out from the probe; after being reflected by the liquid surface, these echoes are detected by the probe. The echo signal is processed using a proprietary algorithm to determine the time t, and the system calculates the liquid level height based on a formula. H = v × (t/2 – tg/2) × α. H: liquid level height; v: speed of sonar waves in the liquid; t: time taken for the sonar waves to travel from emission to return; tg: time taken for sonar waves to propagate through the tank wall; α: correction factor. IV. Installation of liquefied gas level gauges in horizontal tanks – Installation of external-type level gauges for liquefied gas, temperature calibration mode. V. Advantages of installing external-type level gauges in liquefied gas storage tanks: 1. The development of a two-wire system, which overcomes various technical challenges, enabling the creation of successful two-wire external-type level gauges. The two-wire external level gauge achieves ultra-low power consumption, meets the standards for two-wire instruments in industrial environments, simplifies the wiring requirements on site, and is more suitable for safety and explosion prevention purposes. 2. Non-contact liquid level measurement: it enables true non-contact measurement safely, greatly simplifying installation and maintenance. 3. An advanced automatic power control algorithm enables the use of higher power when the liquid level is high, thus eliminating or minimizing blind spots, and lower power when the liquid level is low, with automatic switching of the probe’s power level. It increases the measurement range while reducing the measurement blind spot. This enables measurement with a small blind area, or even without any blind area at all. 4. The external level gauge features extremely high measurement accuracy, reaching 1‰FS. Functions such as the built-in bottom limit wave suppression feature, automatic power control algorithm, and automatic sampling rate control algorithm significantly enhance the measurement accuracy; in some practical applications, the absolute accuracy is as high as 1 cm. 5. The temperature of the storage tank can be measured in real time, and the temperature signal can be transmitted remotely; it is possible to measure the tank temperature in real time and transmit this signal either as an analog or digital value. 6. Real-time temperature calibration improves the accuracy of measurements. The temperature of the storage tank can be measured in real time, with some degree of temperature compensation applied. For common substances such as liquid ammonia, propylene, propane, and LPG, sound speed compensation can also be used to further enhance the accuracy of measurements. 7. Automatic calibration and self-diagnosis functions: The external-mounted level gauge features an automatic calibration function, which overcomes the problem of reduced accuracy in traditional level gauges after long-term use. It enhances the reliability and stability of the external level gauge for its own operational status and hardware diagnostic functions. 8. Pipe calibration: This function is activated automatically when the liquid level falls below half. In such cases, the calibration probe located on the side cannot perform proper calibration; therefore, the level gauge switches to pipe calibration, using the inlet and outlet pipes for real-time calibration in order to further improve measurement accuracy. 9. Real-time tracking across the entire range: there is no need to restart when filling an empty tank. Whether the tank is empty or contains liquid, and regardless of the liquid level, the level gauge can perform real-time tracking across the entire range. 10. The installation and calibration of external level gauges are greatly simplified. These gauges feature high levels of intelligence, which reduces the need for on-site installation and calibration tasks, enabling a foolproof installation process. 11. There are various options for the indicators displayed by level gauges; they can show the remote-level reading, percentage of level, volume, mass, etc. 12. The external level gauge with relay output can provide single-point or dual-point alarm outputs.