18 The MMD Hea vy -Duty Apr on Plate Feeder T he apr on pla t es , which ar e fx ed t o the chain, ar e made fr om specially r olled sec tions and ar e manufac tur ed in v ar ious widths t o ca t er f or the maximum v olume of ma t er ial which ma y need t o be pr oc essed . T hese pla t es ha v e o v er lapping edges pr ev en ting spillage bet w een the pla t es , and ar e fx ed t o the chains with bolts tha t ar e positioned bet w een the g r ousers , pr ot ec ting the bolt heads fr om damage caused b y the ma t er ial being c on v ey ed . T he elimina tion of impac t ener gy is of special impor tanc e . T he impac t f or c e is initially absor bed b y the c on v ey or pla t es , which def or m within their elastic limit . T he impac t r ails then tr ansmit the f or c es which ar e dissipa t ed in t o the main fr ame c onstruc tion. T o c omplemen t the capacit y and str ength of the T win S haf t M iner al Siz er , MMD has desig ned Hea v y D ut y A pr on P la t e F eeders t o c on v e y r a w ma t erial t o the crushing plan t . D esig ned t o handle impac t loads and abr asiv e ma t er ials , they ar e of t en ar r anged benea th tipping poin ts , wher e their c ombina tion of r eliabilit y and r obustness ha v e pr o v en t o g iv e man y y ears of tr ouble fr ee oper a tion with minimal main t enanc e . T he main f ea tur es of an MMD A pr on P la t e F eeder ar e the hea v y dut y chains and r ollers which ar e a ttached t o the main fr ame . T he chains and r ollers v ar y in siz e depending on the applica tion and str esses they will be put under . Chains and r ollers ar e manufac tur ed b y C a t er pillar and desig na t ed as D4, D7, D9 and D11 chain and r ollers . Subsequen tly a F eeder is initially ca t egor ised as D4, D7, D9 or D11. T he F eeder length is measur ed fr om the c en tr e -line of the tail spr ocket t o the c en tr e -line of the head spr ocket , and v ar ies depending upon the pr ojec t r equir emen ts . T he dr iv e loca t ed a t the head spr ocket is gener ally a v ar iable speed unit as it is of t en the main method of c on tr olling the thr oughput of the plan t . T her e ar e t w o t ypes of v ar iable speed dr iv e a v ailable , h y dr aulic , and elec tr o -mechanical . MMD A pr on P la t e F eeders ar e also a v ailable with an in-built fnes r etr iev al sy st em. T he emplo ymen t of cleaning scr apers w elded t o selec t ed c on v ey or pla t es br ing the fne ma t er ial t o the t op of the f eeder t o be deposit ed with the r est of the ma t er ial , elimina ting the need f or a separ a t e fnes c on v ey or . T ype Ef ec tiv e W idth O v er all W idth O v er all Heigh t D4 1,500mm 2,160mm 1,200mm D7 2,000mm 2,775mm 1,480mm D9 3,000mm 3,990mm 1,960mm D11 4,000mm 5,025mm 2,260mm T ypical A pr on P la t e F eeder key dimensions: D7 A pr on P la t e F eeder with F ines R etr iev al S y st em D4 A pr on P la t e F eeder installed in a c onfned spac e D9 A pr on P la t e F eeder f or ming par t of the F ully M obile Slewing Siz er S ta tion