7/25/2019 Update on JHEP SAG Mill Drive Selection
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Update on JHEP SAG mill
drive selection
Dual pinion versus Gearless in
view of changes to AGMAstandards
7/25/2019 Update on JHEP SAG Mill Drive Selection
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Selection concerns
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Gear design improvements leading to increased tolerances to Hertzstresses in mating gear teeth
7/25/2019 Update on JHEP SAG Mill Drive Selection
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Hertz stresses a short description
!ommon misconceptions" #he $ending stress alone does not de%ne the ma&or
dimensions of the gears' such as pitch diameters or centredistance( A compliance with Hertz stress limits does(
E)ciding allowa$le Hertz stresses will lead to severe pittingof the tooth surface and tooth failure due to su$surfacecrac*ing of the tooth material(
Hertz stresses can $e reduced $+ enlarging gears'improving gear hardness and surface %nish' and provision ofade,uate lu$rication(
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E)amples of destructive pitting in gears
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!omparison of AGMA standards for spur-helical gearsfa$rication( AGMA ./0(12 vs( new AGMA 3104-3004
A need for a new' more rela)ed standard originated fromthe fact that the old standard vastl+ ignored progress in theaccurac+ of gear cutting process and signi%cantimprovements in the gear material ,ualit+( #he newstandards are still maintaining gears safet+ factors 5servicefactors)
Hertz contact stress resistance or pitting 6 a durability
factor descri$es a$ilit+ to resist formation of pits and
crac*s in the tooth 7an*s( 8t is a function of tooth geometr+'
material hardness ' the ,ualit+ of gears surface %nish
5cutting' grinding and polishing9 and friction $etween
surfaces of the mating gear : 0(;2(
The strength factor descri$es a$ilit+ to withstand the
7/25/2019 Update on JHEP SAG Mill Drive Selection
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A t+pical meshing of a spur gear
#ooth relieve drawing
7/25/2019 Update on JHEP SAG Mill Drive Selection
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A signi%cant di?>9 use a AGMA >1? to determine geometr+
factors that ta*e into account the a$ove(
AGMA 3004 allows for gear design with 0/;2 mm gear face width(
#he new standard reduces the prescri$ed width of the gear face for a given
load $+ a whooping 2@ (
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Summarising 6 gears designed to AGMA ./0(12 havepotentiall+ more in reserve meaning the+ should $e
a$le to transmit more that the+ were designed for $etter than 01@ ( #he new AGMA 3104-3004 e)ploresthat 01@ allowing for $igger load transfer without
compromising the gear safet+ factors(
In short, it is a very clear that a SAG mill ringgear designed for 22.5M in AGMA !2".#5 ismore than su$cient for 2%M in AGMA"%'&""%.
#he cost savings resulted from the revision ofstandards' averages to a more than 2@ per a set ofgears(
7/25/2019 Update on JHEP SAG Mill Drive Selection
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Girth Gear improvements in casting techni,uesand materials
MAGMA will evaluate di
7/25/2019 Update on JHEP SAG Mill Drive Selection
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Gear =a$rication
!urrent a$ilit+ to cut gears for large' girth gear driven SAG mills is
restricted to" 03 meters in diameter : 2/(2 feet
0(/ meters in face width
/21 tonnes of machined weight
..1 mm thic*' ..1 BHC hardness 6 steel $ending a$ilit+ for afa$ricated' steel girth gear(
All parameters a$ove are good for a //(2M to /4M dual pinionSAG mill drive(
!hanges to AGMA standard have revitalised the large gear cuttingindustr+ and soon a machine shop in Holland will $e a$le to fa$ricategears of the following parameters"
/1 meters in diameter : 32(3 feet 0(2 meters in face width
411 tonnes of machined weight(
A full+ climate controlled facilit+ in Holland will $e read+ forproduction in /10/(
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/4M ing Gear and Pinion calculations
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A simple capital cost comparison 6 dual pinion vs(gearless
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Additional considerations in selection of JHEP SAGmill drive
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!oncrete madness 6 foundations of SAG Mill gearless drive
A gearless drive will re,uire a$out /21@ more concrete and more importantl+more reinforcing steel in the foundations than the e,uivalent dual pinion drive :
FFFFFFFFFFFFFFFFFF#his picture shows onl+ what is a$ove the ground( Ma&orit+ of concrete is $elowthe surface
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=a$rication in !hina 6 ME#S report on ,ualit+ issues
=undamental o$servations-issues"
A principle of collective harmony 6%rst de%ned $+ !onfucius' is re7ected inattempts to please ever+one and enforce compromises resulting in signi%cantlapses in ,ualit+ control(
#his principle does not appl+ in !hina onl+( All populations su$&ected to adictatorship and willing to accept it' displa+ the same trait 6 what a$out JuliaI
Harmon+K ma+ ma*e a foundr+ agree to increase output signi%cantl+without an increase in casting pits' melt ovens' or other capacit+(
Harmon+K ma+ translate into running one cutting machine at faster speeds'while a second is down for repairs' in order to maintain production rates( 8nthe interim' the customerLs compromiseK to this harmon+K ma+ $e toaccept poorer surface %nishes(
Harmon+K ma+ even a
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8nstallation issues
8nformation shared with" utotec' !8#8! and ME#S