Failure Analysis of the Aircraft Accessories Graphite Seal Ring

Abstract

After 1300 hours of operation, the aircraft accessories graphite seal ring parts were overhauled with the aircraft engine. Then the seal assemblies were reinstalled on the engine. The graphite seal ring fractured 1 hour of used. The failure cause of the graphite seal ring was analyzed by appearance inspection, structure relationship analysis of the seal parts, surface and fracture observation, physical performance testing and composition examination. The analysis results show that the physical performance of the failed graphite seal ring met the requirement, and no abnormality was observed in the structural composition. But in the long-term used process, there was mutual wear between the fixing groove of the graphite seal ring and the limiting bracket of the metal static ring seat. As a result, the operating space of graphite seal ring was increased. The overall coordination stability decreases after the secondary assembly. Therefore, when the engine starts, the fluctuating friction occurs between the graphite seal ring and the friction pair, and the lubrication condition was poor, resulting in the graphite ring carrying capacity was too large, and then led to the graphite ring fracture in a short time after maintenance. This leads to fracture of graphite ring in a short time after overhaul. In order to prevent the failure from happening again, this paper gives the corresponding improvement suggestions.