Rope RF Admittance Level Switches Applied in Coal Silos of Power Plant

Jiangsu Ligang Power Plant is a large-scale thermal power plant. In coal-fired process, a large amount of coal ash is generated, which is usually collected in the silo. In order to avoid the storage of coal ash, it is crucial to detect and control the level of coal ash. The power plant expects to realize high level (3 meters) switch alarm signal through the level sensor in each coal bunker and silo, so as to avoid the occurrence of silo overflow.

Importance of coal silo level measurement

Silo is widely used in power systems, mainly used for coal and coal ash storage. The storage of coal ash can reduce environmental pollution caused by coal ash and conform to the regulations of industrial environmental protection. However, if coal ash overflows, it will produce dust and pollute the atmosphere. If it enters into the water system, the river will be silted up, and the toxic chemicals will also cause harm to human beings. Therefore, to avoid the occurrence of overflow accident, the power plant has high requirements for measuring instruments to ensure the stable and reliable measurement of coal ash level.

Difficulties in coal silo level measurement

The silo coal storage capacity of Ligang Power Plant is about 30000 tons, the height of coal bunker is as high as 30 meters. Raw coal is grinded into powder by coal mill and transported into the silo through pipeline. Due to the fast and frequent filling speed, the flying dust is everywhere in the silo, plus the dust is heavy when medium filling, so the working condition is relatively serious. At present, there are many kinds of level measuring instruments, such as: Rotary Paddle Switch, Tuning Fork Level Switch, Radar Level Meter, etc. Because those measuring sensors are limited by the measurement principle and field conditions, for example, the radar level meter is measured according to the principle that part of the energy is reflected back when the transmitting pulse contacts the surface of the measured medium. However, there is a large amount of flying dust in coal silos, and the dust will interfere with the radar level meter by its reflected signal, resulting in false echo and affecting the measurement accuracy. Although rotary paddle switch and tuning fork level switch can output the switch alarm signal, they are more suitable for small range measurement.

Rope RF admittance level switch and its characteristics

Combined with the actual working conditions of power plant, Jiwei engineer recommended Cape-11R Rope RF Admittance Level Switch. Cape-11R Rope Admittance Level Switch uses probe to sense the change of capacitive reactance and impedance between the probe and the vessel while detecting the material position. Within the electronic unit, the probe’s measuring pole and the reactance of empty vessel together form a balanced bridge circuit and generate a stable oscillation signal. When the level rises and measured medium covers the probe, the reactance between the probe and vessel wall changes, which causes imbalance of the bridge circuit, and stops generating an oscillation signal. This change will be detected by the circuit, and then output an alarm signal. Cape-11R is suitable for large tank silos, its vertical installation method can effectively avoid material impact.

Features of Cape-11R Rope Admittance Level Switch

●　Based on the dielectric constant of coal ash, specially designed for coal ash level measurement.

●　Suitable for larger tanks and silos level measurement.

●　With an external dual color LED indicator and the housing with electronics can be rotated during installation to make orientation of the LED convenient for long distance observation.

●　Modular design for high reliability, easy installation and maintenance.

●　Passed third party reliability test and received certifications from the third party, extremely high reliability guaranteed.

After comprehensive comparison, the power plant first purchased Cape-11R Rope Admittance Level Switch in small batches. After all the instruments have run for a period, the stability, safety and reliability have convinced the user, so the user decided to replace all imported Siemens admittance level switches to Jiwei Cape-11R Rope Admittance Level Switch to measure the level of coal silos in the power plant. The high cost performance ratio makes the user decide to establish a long-term plan with Jiwei. Currently, more than 100 sets of Cape-11R Rope Admittance Level Switches have been purchased by users.