Abstract
In coal mines, bolt loosening in the cage guide is affected by the harsh environmental factors and cage hoist vibration, leading to significant threats to work safety. It is crucial, to this effect, to successfully detect the status of multipoint bolts of guide structures. This paper proposes a system to monitor bolt status in harsh environments established based on the RFID technique. A proof-of-concept model was demonstrated consisting of a bolt gearing system, passive UHF RFID tags, a reader, and monitoring software. A tinfoil metal film is fixed on the retaining plate and an RFID tag bonded to a large gear, with the bolt to be detected fixed in the center of a smaller gear. The radio-frequency signal cannot be received by the reader if the tag is completely obscured by the tinfoil, and if the bolt is loose, the tag’s antenna is exposed when the gear revolves. A radio-frequency signal that carries corresponding bolt’s information is transmitted by the RFID tag to the RFID reader due to coil coupling, identifying loose bolt location and reporting them in the software. Confirmatory test results revealed that the system indeed successfully detects bolt loosening and comparative test results (based on a reed switch multipoint bolt loosening monitor system) provided valuable information regarding the strengths and weaknesses of the proposed system.
Highlights
Bolt joints, a common component of large-scale steel equipment and structures, are widely used in aeronautic, civil, mechanical, chemical, and other industries [1,2]
When the tag is in the effective working area, induced current is produced in the electronic code, and the radio frequency signal of a particular frequency is sent by the radio frequency identification (RFID) reader tag due to coil coupling, and as a result, the tag is able to acquire energy to send its own coded to the tag
An innovative approach to the loose bolt problem in coal mine cage guide structure, which is caused by harsh environment and many other factors, was developed in this study
Summary
A common component of large-scale steel equipment and structures, are widely used in aeronautic, civil, mechanical, chemical, and other industries [1,2]. The personal safety of mine workers is directly affected by bolt joints typically applied in coal mine cage guides. Bolt loosening is mainly judged by bolt fastening force testing, primarily through the torque wrench method or ultrasonic detection method. To conduct the ultrasonic detection method, an ultrasonic probe is mounted on the bolt to measure fastening force by ultrasonic echo. The harsh environment in the coal mine makes it especially difficult to detect bolt loosening, in addition to the fact that the coal mine cage guide is usually several hundred meters long, making monitoring such a large number of bolts at the same time very difficult. We developed an RFID technique based on passive monitoring [11,12,13] to monitor bolt loosening in cage guides. The performance of the combined hardware and software is verified in a simulated re-entry environment to determine whether the developed prototype diagnoses bolt loosening with sufficient reliability and accuracy
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