Fiber Optic Temperature Monitoring of Belt Conveyors

Major conveyor belt–related mining incidents are now relatively infrequent as a result of recent improvements in engineering standards and the use of fire-resistant materials. However, conveyor belts are still a potential cause of personal and structural damage. In addition, any unexpected breakdown of rolling components or failure of belts creates a significant interruption to production, which is a major concern for operators, who are responsible for achieving optimum mining production. This project aimed to develop a fiber optic-based distributed temperature sensing (DTS) system to monitor the temperature change of malfunction idlers for heavy-duty conveyor belts in underground coal mines.
Conveyor belts have been widely used for centuries to transport general goods, bulk materials, and passengers. Conveyor belts have attained a dominant position in the continuous conveying of bulk materials ranging from very fine, dusty chemicals to bulk materials, such as raw ore and coal, as well as for overburden, including stones, soil, and logs of wood. In comparison to other transportation methods for bulk solids, such as trains or trucks, conveyor belts are an extremely favorable choice in instances where suitable infrastructures for other modes of transport do not exist.
The main fire risks associated with belt type conveyors are as follows:
› Friction due to loss of belt traction and slipping on the drive roller;
› Welding activities can generate hot molten material;
› Overheated materials placed on the belt;
› Build up of materials that have fallen off the belt and dust cloud generation;
› Static electricity.Continue reading

Fiber Optic Sensors for Vibration Monitoring

Vibration is a common phenomenon in nature and vibration monitoring technology is of significant importance in scientific measurements and engineering applications. Accurate measurement and monitoring of vibration are crucial for the detection of the abnormal events and pre-warning of infrastructure damage. Traditional vibration sensors suffer from electromagnetic (EM) interference, which presents the difficulty for applications in harsh environments. In addition, the short monitoring distance and high maintenance cost mean they do not meet the actual needs of modern engineering measurements.

Optical fibers have attracted a significant amount of research attention in a wide range of applications during the last several decades due to the outstanding advantages of lightweight, flexible length, high accuracy, signal transmission security, easy installation, corrosion resistance, and immunity to EM interference. These characteristics render them attractive for use in harsh environments where the application of traditional sensors is severely limited. The high sensitivity to changes in external physical quantities, such as temperature, strain, and vibration, makes optical fibers suitable for sensing purposes. Up to now, fiber-optic vibration sensors mainly consist of the point, quasi-distributed, and distributed sensors. Several schemes of point sensors including fiber Bragg grating (FBG), Fabry–Perot, self-mixing, and Doppler vibrometry are deployed for vibration measurement. Among them, FBG vibration sensors have become a fast-developing scientific research field owing to intrinsic advantages such as low noise, good embeddability, and the ability to be easily multiplexed to construct a distributed sensor array. Based on the FBG sensing principle, many investigations are applied to the measurement of vibration. Distributed fiber optic vibration sensing technology is able to provide fully distributed vibration information along with the entire fiber link, and thus external vibration signals from an arbitrary point can be detected and located. Compared with point and quasi-distributed vibration sensors, which can only be used individually on a small scale and often have poor concealment, distributed fiber-optic vibration sensors inherit the advantages of general fiber sensors and offer clear advantages such as lightweight, large-scale monitoring, good concealment, excellent flexibility, geometric versatility of optical fibers, quick response, system simplicity, immunity to EM interference, high sensitivity, accurate location, etc. Distributed fiber-optic vibration sensors mainly include interferometric sensors and backscattering-based sensors. Various interferometric sensors have attracted a significant amount of research attention and are widely investigated.

Continue reading