Vibration Signature Based Condition Monitoring of Bowl-Roller Coal Pulverizers

The overall objective of the work reported in this paper is to minimize the cost of power generation in thermal power stations utilizing pulverized coal combustion processes for steam generation. The strategy of achieving this objective is based on an “on-condition maintenance” philosophy and vibration based diagnostic signature analysis techniques. The coal pulverizers reported on here are 783 RP (roll pressure) and 823 RP combustion engineering (CE) bowl-roller coal pulverizers (bowl mills) installed at the State Energy Commission of Western Australia (SECWA) power stations. This paper reviews the design philosophy, operational principles, and system dynamics and establishes the procedures for identifying the potential malfunction of bowl mills and their associated components. The influence of operating parameters, such as coal flow, primary air flow, and operating temperature, on mill vibration are investigated. The effects of journal spring force variation, such as magnitude, uneven spring force, and broken springs, are also studied. Special attention is also given to the diagnosis of the top radial bearing problem due to its remoteness from the bowl mill external structure. A spectral recovery technique utilizing the inverse frequency response function was developed for trend analysis and diagnostic purposes.