Diagnosis the cause of the crack on the bucket wheel boom on the excavator ERs 1250 Gacko

Abstract

Bucket wheel excavator ERs 1250 in Gacko has worked for over 30 years. Excavator was working in very difficult conditions because it was exploited very solid material which negatively affected the dynamic behavior of the whole structure. Bucket wheel boom of the excavator is a single tube approximately 20m long. Finite element method was applied in calculations and the results are presented in the paper. The first calculation was performed for two load cases. One case was for the complete usage of engine power (the worst case) and the other was static analysis based on the inertial load of the bucket wheel and the drive group. Measurements of deformations and vibrations on the bucket wheel boom were performing during process of digging. Strain and stress measurements were obtained using inductive sensors and eddy current sensors. These sensors measure the change in length between the magnets placed on the measuring points. Experiments and calculations gave the same results that show the negative effect of dynamic forces acting on a boom. Earlier this year the crack was discovered in a cylindrical root of the tube nearly 270 of its scope. Previously derived calculations and measurements didn’t indicate the possibility of the crack appearance. Therefore, additional simulations of load were performed (horizontal and vertical unit loads) that could cause the crack. Numerical analysis has shown that the horizontal force in the amount of 1000 kN could cause such a large crack.