Application Case of Dinghua External Level Gauge at Tianjin Dagu Chemical Plant

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This post was last edited by Xidian Dinghua Electronics on 2019-8-20 at 17:10. Case study of Dinghua external level gauges in Tianjin Dagu Chemical Plant. Tianjin Dagu Chemical Co., Ltd., formerly known as Tianjin Dagu Chemical Plant, was established in 1939. It is a large-scale chlor-alkali enterprise that focuses on salt electrolysis as its foundation and aims to develop the marine chemical and petrochemical industries; it produces a variety of products such as caustic soda, polyvinyl chloride resin, propylene oxide, polyethers, liquid chlorine, and synthetic hydrochloric acid. As a company that has obtained ISO9002 quality system certification, Tianjin Dagu Chemical Co., Ltd. has implemented a series of reforms and innovations in order to achieve and maintain an excellent standard of product quality. Technologically, production facilities for ion-exchange membrane caustic soda, propylene oxide, and PVC produced by the ethylene oxychlorination method, all of which are at the international advanced level, have been introduced one after another. In the production of its key products such as caustic soda, polyvinyl chloride resin, propylene oxide, and polyethers, microcomputer-based automatic control is employed; the four main parameters in the company’s production processes—temperature, pressure, flow rate, and liquid level—are monitored in real time and managed centrally. Since enterprises have many areas where \"hazardous chemicals\" are stored and used, these chemicals mainly include vinyl chloride, liquefied gas, propylene, phenol, ABS oligomers, butadiene, VCM, and VCM monomers. High standards are required in terms of safety and environmental protection; therefore, measuring instruments must operate without any failures, and even in the event of a failure, they must not pose risks such as combustion, explosion, or leakage. This imposes even higher safety requirements on such measuring instruments. Previously, magnetic flap level gauges, differential pressure level gauges, and an imported radar level gauge from a certain brand were used on these tanks. Due to the presence of deposits in some fluids and impurities in others, especially the problem that VCM monomer is volatile and prone to self-polymerization, level measurement has always been a challenge. With magnetic flap level gauges and differential pressure level gauges, the connecting parts of the pipelines get blocked after being in use for a while, requiring cleaning, maintenance, and re-calibration ； The emission port of the radar level gauge is covered by volatiles and self-polymerizing substances; before maintenance, it is necessary to empty the tank and replace the contents, a process that is very complex and requires significant effort, thus having an adverse impact on the company’s daily production. In 2000, a new type of level measuring instrument was introduced – the ELL sonar external level gauge, which does not require tank emptying, welding, or making holes in the tank for installation, calibration, or maintenance. Due to its easy installation, all that is needed is to attach a sensor to the bottom outside the tank and connect it to a transmitter, which will then display the liquid level; debugging does not interfere with normal operation. In March 2001, as the manufacturer of this new type of instrument, Dinghuana installed and tested it by choosing chlorine vinyl monomer (VCM) storage tanks, where it is difficult to measure the liquid level. The fluid in such tanks is volatile and tends to polymerize, and there are sediment layers at the bottom of the tanks; therefore, an ELL sonar-type external level gauge model AE was installed on these tanks. After 3 months of use, the gauge has operated stably, provided accurate level readings, and offered reliable remote transmission, fully meeting the user’s requirements for level measurement.