Failure analysis of scraper conveyor based on fault tree and optimal design of new scraper with polyurethane material

The scraper conveyor is an important equipment in modern coal mining process. Traditional alloy steel scrapers, as one of the main components of the scraper conveyor, are disadvantageous in that they are not only vulnerable to failures such as fracture and wear, but also take up over 35% of the output power to rotate themselves, resulting in excessive idle load. In order to improve the running state of the scraper and the overall loading of the scraper conveyor and extend the service life of the scraper, a transportation system fault tree of the scraper conveyor was drawn based on fault tree analysis. The minimum cut set of the fault tree was calculated. The Fussel–Vesely importance (FV) of scraper failure to transportation system was 0.458. Failure of the original scraper primarily includes wear and fatigue, as result from the excessive wear caused by the sliding friction between the scraper and the middle trough. A new optimized scraper design was developed: the support was forged from PU material to reduce self-weight and increase buffer capacity; the scrape was restructured to include rolling elements and a detachable support, which transformed sliding friction to rolling friction. Use of the new scraper in a mine reduced the idling rate of the scraper conveyor to 23% and increased the scraper service life by around 3 times. The research result of this paper could provide reference for further application of lean design theory in the updating of coal mining equipment.