Please discuss the design and improved application of dual-level systems. I earnestly request your valuable suggestions.

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Level measurement is one of the most important parameter measurements in the control of chemical production processes, and it holds the same significance as temperature and pressure measurements. Therefore, level measurement is widely used in various positions. However, like other instruments, level measurement devices can also experience accidental failures and malfunctions. Therefore, for ordinary level measurements, it is likely not to have an impact on production ； However, for the level control of critical equipment in certain positions, the level measurement devices must not fail, as this could disrupt production and even lead to safety accidents. Case 1: On September 7, 2005, fluctuations occurred in the automatic level control of the decarboxylation tower; it took a week to resolve the issue, which had a certain impact on the stable production of urea. Case 2: On April 16, 2006, the dual-flange level auto-control system in the urea and liquid ammonia buffer tank reached its maximum level, nearly causing a shutdown of the urea production process. Even the strongest person can catch a cold and have a fever, and even the best equipment can malfunction. Therefore, to ensure accurate and reliable control of the liquid level indication for these critical devices, we have installed an additional set of differential pressure level gauges as a comparative indicator, enabling dual liquid level measurement with one primary and one secondary gauge – essentially a \"double safety mechanism\". This also reflects the management concept of equipment “backup” – having backup units, whole machines, components, and parts. So, what is a “dual-level” measuring device? In short, it involves measuring the liquid level of a device by installing two sets of liquid level measurement instruments to display that device’s liquid level ； The level involved in process control operations is referred to as the main liquid level, while the level used for on-site level comparison indication is called the secondary liquid level. Once the main liquid level shows abnormal readings or malfunctions, operators can refer to the secondary liquid level for judgment, or rely on the secondary liquid level to carry out operations. To date, we have utilized the resources at our disposal to install dual-level sensors on certain equipment, thereby providing a double layer of protection: the decarboxylation tower (2006), the liquid ammonia buffer tank (2006), the pure alkali tower (2005), the desulfurization cooling tower (2005), and the three-gas drum (2003), among others. In fact, the drum liquid level of our boilers is monitored using dual levels (one remote reading and one on-site measurement); in some cases, there are even three levels (one remote reading and two on-site measurements) or four levels (two remote readings and two on-site measurements) ； It is evident how important the drum level control operation is. Case 3: On June 13, 2004, a leak occurred in the level gauge valve on the east side of the three-gas boiler. During repairs, the technician closed the root valve, which resulted in malfunction in the control of the drum liquid level. Fortunately, the operator promptly used the level gauge on the west side to compensate, thereby preventing any impact on production. Now, we are continuously promoting the concept of \"redundancy\", such as on-site redundancy: dual levels, dual flow rates, dual power supplies, etc. Only when the instrumentation hardware remains “permanent” and undamaged can it provide a stable and reliable basis for operations. Furthermore, the use of two liquid levels also provides a basis for electrical and instrumentation technicians to conduct inspections; if the indication errors of the two liquid levels are within the allowable range, it indicates that their readings are correct ； If it exceeds the specified range, it indicates that there is a measurement error in one of the liquid levels, and an immediate inspection is required.