update on jhep sag mill drive selection

7/25/2019 Update on JHEP SAG Mill Drive Selection

1/20

Update on JHEP SAG mill

drive selection

Dual pinion versus Gearless in

view of changes to AGMAstandards


2/20

Selection concerns


3/20

Gear design improvements leading to increased tolerances to Hertzstresses in mating gear teeth


4/20

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(


5/20

E)amples of destructive pitting in gears


6/20

!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


7/20

A t+pical meshing of a spur gear

#ooth relieve drawing


8/20

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@ (


9/20

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(


10/20

Girth Gear improvements in casting techni,uesand materials

MAGMA will evaluate di


11/20

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/(


12/20

/4M ing Gear and Pinion calculations


13/20

A simple capital cost comparison 6 dual pinion vs(gearless


14/20

Additional considerations in selection of JHEP SAGmill drive


15/20

!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


16/20

=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


17/20


18/20


19/20


20/20

8nstallation issues

8nformation shared with" utotec' !8#8! and ME#S

update on jhep sag mill drive selection

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