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During the renovation of tank areas, low and high liquid level alarms are associated with issues such as difficulty in opening tanks, time-consuming and labor-intensive tank cleaning, and inconvenient maintenance. The Dinghua Electronics ultrasonic external level switch is installed on the outer wall of the tank being monitored. Compared with traditional level switches, it does not come into contact with the liquid medium being measured, thus offering strong resistance to interference ； It requires no drilling or welding, and its installation and maintenance are simple and convenient; it represents an excellent measurement method for the renovation of tank areas. The application scenario is to further improve the monitoring and control facilities in the chemical tank area; in accordance with regulatory requirements, high and low liquid level alarms are installed in the storage tanks, and automatic interlocks are used to shut off the feed valves of the tanks when the liquid level is too high, as well as to stop the discharge of materials when the liquid level is too low. A factory encountered two problems while installing low-low liquid level switches for automatic interlock pump shutdown. Firstly, the float level gauges used in the natural gas tanks in the old tank area have a single measurement method, which does not meet the requirements of the alarm and interlock control systems. During the renovation of this tank area, it is necessary to install level switch alarm devices that transmit relay signals to the core control system to enable interlocking. Secondly, when installing level switches in tank areas, traditional intrusive, buoyancy-based, pressure-based, capacitive, and fork-type level switches require openings for contact with the medium. It is difficult to make such openings in old oil tanks, cleaning the tanks takes a long time, and there is a risk of leaks; hence, this approach is neither economical nor safe. Principle of the ELL ultrasonic external level switch: The ELL ultrasonic external level switch is a type of level switch that utilizes the principle of attenuation of ultrasonic waves as they propagate through walls, combined with \"frequency-modulated ultrasonic\" technology for detection; it operates on a resonant mode. The measuring probe is attached to the outer wall of the container; it is a completely contact-free, isolated instrument for detecting liquid level from outside the tank. It can be widely used for level detection of various liquids. The ELL ultrasonic external level switch’s measuring probe emits ultrasonic waves and detects the reverberation signals in the container wall; when the liquid covers the probe, the amplitude of these reverberation signals decreases. Upon detecting this change, the instrument generates a switch signal. “\"Variable-frequency ultrasonic technology\" is a world-leading ultrasonic signal variation detection technology invented by Dinghua Electronics. The main problem with traditional ultrasonic level switches is that the ultrasonic signals are affected by deposits on the tank walls, and they experience drift over time and with changes in temperature, which alters the amplitude of the residual vibration signals and thus leads to false alarms. By utilizing its patented adaptive adjustment \"variable-frequency ultrasound technology,\" Dinghua Electronics is able to effectively eliminate interference and drift, accurately detect signal changes, and thus operate reliably over the long term in various complex field conditions. Thanks to the use of Dinghua Electronics’ \"micro-vibration analysis\" external sonar signal processing technology and advanced manufacturing processes, the ultrasonic external level switch ensures reliability and durability. Product features and advantages of ultrasonic external level switches: 1. Safety: When measuring liquids that are toxic, corrosive, under pressure, flammable, explosive, volatile, or prone to leakage, these switches do not require the use of valves, connecting pipes, or fittings; there are no leakage points, and they do not come into contact with the liquids and gases inside the tank, making them highly safe. Even when the instrument is damaged or under maintenance, there is absolutely no possibility of leakage, poisoning, or explosion. 2. Reliable and durable: Utilizing Dinghua’s advanced signal processing technology and manufacturing processes, it is reliable and durable. 3. Precision: Up to ±1mm. 4. Easy to install and maintain: Installation and maintenance can be carried out without the need for heating or emptying the tank, thus not disrupting production. 5. Wide applicability: Not restricted by the pressure, temperature, density, dielectric constant, viscosity, or corrosiveness of the medium being measured inside the tank. 6. Technical leadership: Features unique self-diagnosis for faults, along with a design for transmitting fault signals over long distances ； The instrument comes equipped with lightning and surge protection, eliminating the need for an additional surge protector. 7. It has obtained the SIL3 certificate by passing the “Functional Safety Integrity” level certification from the Shanghai Instrumentation and Automation System Testing Institute. Applications of ultrasonic external level switches: 1. Installation: The container wall at the location where the sensing probe is installed should be made of a rigid material that can transmit vibrations effectively. If the container wall is composed of multiple layers, these layers must be in close contact with each other, without any bubbles or air gaps, and the inner and outer surfaces should be smooth. Do not use other ultrasonic or electromagnetic devices in the vicinity, to avoid interference between them that could cause malfunction. The storage tanks in our plant’s tank area are ferromagnetic; they can be secured using the magnetic force of strong magnets. Cables can be laid using the existing supports, and installation can be carried out without shutting down production, without the need to empty the tanks, and without any use of fire. Our factory has employed ultrasonic external level switches in the process of adding automatic interlock pump shutdown based on high liquid level sensors. The two probes of the level switch must be arranged horizontally on the tank wall; there should be no welds or similar elements between them, and each probe should also be placed as far away from welds as possible. 2. The company has multiple horizontal liquefied gas storage tanks. Each storage tank is equipped with only one set of magnetic flap level gauges. During use, some of these gauges experienced problems such as the magnetic float getting stuck or inaccurate measurements, which posed safety risks to the safe operation of the tank area. During the technical upgrade, an additional set of ELL external level gauges was installed in each storage tank. The upgrade was completed without the need to shut down the tanks and empty them, thereby enabling accurate measurement of the liquid levels in the tank area and eliminating the safety risks associated with inaccurate level measurements. In summary, the ultrasonic external level switch is performing well in our company’s tank area, and no issues have been encountered so far. Due to the many advantages of ultrasonic external level switches, the use of this type of device in tank farm renovation projects is becoming increasingly widespread. The functions for detecting tank levels are constantly improving, the measurement accuracy is getting higher and higher, and there are more and more successful examples of tank farm renovation projects. Several years of actual field use in the plant’s tank area after its renovation have shown that ultrasonic external level switches are easy to install and operate, possess strong resistance to interference, require minimal maintenance, and offer high safety performance. As an ideal new type of contactless level alarm instrument, the external measurement type level switch effectively provides low-level alarm functions. It ensures the safety of liquid levels in storage tanks, reduces maintenance efforts, and eliminates the safety risks associated with working near open areas in tank areas during renovations. It can be widely used for level monitoring in harsh environments in industries such as petrochemicals.