Estimated safe residual service life of a 29-year old BOF trunnion pin

摘要

An engineering study of the fatigue cracked No.1BOF trunnion pin has been completed. A finite element stressanalysis and ultrasonic survey of this trunnion pin have been usedto estimate a future fatigue crack propagation rate and thepossibility of a trunnion pin fracture similar to the No.3 BOFtrunnion pin fracture that occurred in Dec.1996. The steelproperties of the cracked and removed No.2 pin and the brokenNo.3 pin were used to assist in estimating a safe residual servicelife of the No.1 pin.Although the estimated rate of fatigue crack propagation over thenext few years is small, the possibility of an impact fracture of thisbrittle No.1 pin does exist on the basis of the current size of thefatigue crack.Replacement of the existing No.1 BOF trunnion pin was donewithin a schedule that provided adequate time for properengineering and site preparation. The No.1 pin replacementschedule was not dependent on a future blast furnace relineschedule because failure of the No.1 pin could have occurredbefore the next blast furnace reline.