Hydrostatic Fiber-Optic Liquid Level Sensor with a Position-Sensitive Detector

Monitoring of the level of different flammable liquids is examined, including that of petroleum products in high capacity tanks, as well as during pumping, at oil storage depots. The operating characteristics of most level measurement devices do not meet customer specifications in practice. Commercial accounting for petroleum products requires more precise measurements and more stable operation of the liquid level gauges set up for factory conditions and spark-explosion safe operation. The development of a spark-explosion-safe device with a hydrostatic fiber-optic liquid level sensor and a position-sensitive detector is validated. For continuous monitoring of liquid level, it is proposed that measurements be made of the displacement of the bottom of a bellows under the influence of the hydrostatic pressure created by a column of the liquid with automatic compensation of the change in the density of the liquid. Compensation is carried out with a small buoy with an optical triangulation sensor for small displacements installed in it with a position-sensitive detector. The use of a bellows for suspension of the buoy is justified theoretically. The operating principle of the fiber-optic liquid level sensor is described. The calculated absolute measurement error for the level of a petroleum product is less than ±1 mm. The spark-explosion hazard of the device is reduced because there are no wires in the measurement zone, so the proposed device can be used in different fi re-hazardous media with a corresponding spark safety level confirmed by certification.