The Design of Rolling Bearing Mountings

75 Rope sheave (underground mining)These sheaves are arranged in the head frames of thepits. The rope fastened to the cage runs from the drivesheave or the drum of the hoist into the mine by passingover the rope sheaves.Operating dataStatic rope load 452 kN; weight of rope sheave andshaft 75 kN; rope sheave diameter d S = 6.3 m; haulagespeed v = 20 m/s; wrap angle 140°.Acceleration forces are taken into account by assuming10 % of the static rope load.The recommended index of dynamic stressing f L is4...4.5. With 4.5, the nominal rating life is about75,000 hours. It should be borne in mind that only inrare cases the rope sheave bearings fail due to materialfatigue; usually their service life is terminated by wear.Thus, the required dynamic load rating C for the sphericalroller bearing is calculated as follows:C = f L /f n · P = 4.5/0.838 · 500 = 2,680 kNSpherical roller bearings FAG 23252BK.MB with adynamic load rating C = 2,900 kN were chosen.The bearings feature a high load carrying capacity andcompensate for potential housing misalignments, shaftdeflections and deformations of the head frame.452 kNAdditional load 10 %Sheave andshaft 75 kN452 kN1000 kNAdditional load 10 %Machining tolerancesOne bearing acts as the locating bearing, the other oneas the floating bearing. Both bearings have a taperedbore (K 1:12). They are mounted on the shaft journalwith withdrawal sleeves (FAG AH2352H). Mountingand dismounting is simplified by using the hydraulicmethod. For this purpose the withdrawal sleeves featureoil grooves and ducts. The spherical roller bearingsare supported by FAG plummer block housingsFS3252AHF and FS3252AHL.Bearing selection, dimensioningFrom the parallelogram of forces the resultant load isapproximately 1,000 kN. Since the two bearings aresymmetrically arranged, the radial load per bearing isP = 500 kN.Speed n = v · 60/(d S · π) = 20 · 60/(6.3 · 3.14) =60 min –1 ; this yields a speed factor f n = 0.838.Shaft journal to h6, cylindricity tolerance IT5/2 (DINISO 1101).Housing to H7.Lubrication, sealingGrease lubrication with FAG rolling bearing greaseArcanol L186V.A multiple labyrinth protects the bearings againstcontamination. Replenishment of labyrinth grease iseffected about every 4...6 weeks.FAG 106