3-Productivity Factors [PDF]

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3. Productivity Factors EARTHMOVING 120404 PEMINDAHAN TANAH MEKANIS



Productivity Variable 



Factors that affect the productivity: 1. DIGGING RESISTANCE •



Caused by:







Friction between digger with the material







Material roughness : resisting the scooping process of the digger to the soil







Particle and grain size







Adhesion between digger and soil







Cohesion inter-soil particle







Material density



digging resistance



digging resistance



digging resistance



digging resistance



Rolling Resistance Rolling resistance is the resistance of a level surface to constant-velocity motion across. Rolling resistance results from friction of the driving mechanism, tire flexing, and the force required to shear through or ride over the supporting surface.



Rolling resinstance depends on :



 



Road condition (smoothness and hardness)







Part of the unit which interact to the road surface Rubber 



tire: size, air pressure, quality, tire surface



Crawler track : will affect to the road form



Rubber tire Crawler type Road type



High Pressure



Low Pressure



Avg



lb/ton



lb/ton



lb/ton



lb/ton



55



35



45



40



Good aspalt



60-70



40-65



50-60



45-60



Hard earth, smooth, well maintained



60-80



40-70



50-70



45-70



Dirt road, average construction road, little maintenance



70-100



90-100



80-100



85-100



Dirt road, soft, rutted, poorly maintained



80-110



100-140



70-100



85-120



Earth, muddy, rutted, no maintenance



140-180



180-220



150-220



165-210



Loose sand and gravel



160-200



260-290



220-260



240-275



Earth, very muddy and soft



200-240



300-400



280-340



290-370



smooth concrete



(Source: Peurifoy, et. al., 2006)



Type of Road



RR for Rubber tire (lb/ton)



Hard, smooth surface, well maintained



40



Firm but flexible surface, well maintained



65



Dirt road, average contruction road, little maintenance



100



Dirt road, soft or rutted



150



Deep, muddy surface or loose sand



250-400



RR in Percentage Road Type Concrete rough and dry



RR (lbs)



Rubber Tire



Crawler track



2%



-



2%



-



3%



-



5%



2%



8%



4%



Loose sand and gravel



10%



5%



Deeply rutted dirt, spongly base,



16%



7%



Compacted dirt and gravel, well



maintained, no tire penetration Dry dirt, fairly compacted, alight tire penetration Firm, rutted dirt, tire penetration appprox. 2" Soft dirt fills, tire penetration approx. 4"



tire penetration approx. 8"



Grade Resistance •



The force-opposing movement of a machine up a frictionless slope



•



It acts against the total weight of the machine, whether track by type or wheel type. If a machine moves down a sloping road, the power required to keep it moving is reduced in proportion to be the slope of the road. This is known as grade assistance.



•



D



EF/DE=BC/AC ----> P/W = BC/AC P



P=W. BC/AC dimana AC = AB/cos θ Asumsi w = 1 ton= 2000 lbs. Tan θ = 10/100 ----> θ = arc tan (10/100) maka θ = 60 Cos θ  0.99, A



10 m



w F θ



E 100 m



sehingga P = 2000 lbs x (10 m /(100/cos θ)) = 200 lbs



C



B



Gradient



GR



Gradient



GR



Gradient



GR



%



lb/ton



%



lb/ton



%



lb/ton



1



20,0



9



179,2



20



392,3



2



40,0



10



199,0



25



485,2



3



60,0



11



218,0



30



574,7



4



80,0



12



238,4



35



660,6



5



100,0



13



257,8



40



742,8



6



119,0



14



277,4



45



820,8



7



139,0



15



296,6



50



894,4



8



159,0



Traction Coefficient Represents the percentage of the total engine power that can be converted into forward motion by means of the friction between tire or track







Coefficient of traction or friction refers to the maximum frictional force that can be produced between surfaces without slipping











Traction Coefficient depends on :



1.



Tire condition and Tire Groove or Track Shape



2.



Road condition or material (wet/dry, hard/soft, undulating/even)



3.



The weight of unit which bore by the power train Road type dry, rough concrete



Rubber tire 0,8-1,0



crawler track 0,45



dry, clay loam



0,5-0,7



0,90



wet, clay loam



0,4-0,5



0,70



wet sand and gravel



0,3-0,4



0,35



loose, dry sand



0,2-0,3



0,30



Rimpull 



term that is used to designate the tractive between the tires of a machine’s driving wheels and the surface on which they travel.



HP x 375 x machine efficiency RP(i) = -----------------------------Velocity (i) (mph)



Acceleration 



Time that is needed by the unit to accelerate by using the excess of rimpull amount to drive forward in a certain circumstances







Acceleration is affected by:







1.



Unit weight



2.



Rimpull excess



How to determine acceleration: 1. 2.



a = (F x g)/w Graphic (performance chart)



3.



Empirical : every 20lb/ton of rimpull excess at certain gear will give 1 mins time to achieve maximum velocity which gear shifting is needed



4.



V avg =



V maksimum x velocity factor



Operator (worker) Efficiency 



Operator efficiency is affected by: a. Climate or weather b. Unit or machine condition c. Working environment and culture d. Personality e. Others: Replacement  Lubricant  cleansing  removal  Unfit co-worker  Waiting for progress  Road maintenance 



Rarely worker is doing the job at full 60 mins within 1 hour. The working time ratio to the available time is called by working efficiency. For example within 1 hour, only 50 mins that being used for effective work, so the efficiency will be = 83 %. To improve the efficiency, some efforts need to be done, such us incentives, supervising, reward and punishment



Operator (worker) Efficiency Operator Efficiency is also influenced by mechanical condition of the equipment 1.



Availability Index or Mechanical Availability (AI) illustrates for how much time the unit was available for production and not down for one of the following reasons



AI = W/(W+R) X 100% 2.



Physical availability (PA) represents the percentage of time that equipment is able to operate but may (production time) or may not (standby time, delay time) be "operating" due to reasons other than mechanical limitations PA = (W+S)/(W+R+S) X 100%



3.



Use of availability Showing the percentage of time that being used by an equipment to operate when it is available to work UA = W/(W+S) X 100%



4.



Effective utilization Showing the percentage of time that being used by an equipment to operate on productive work



EU = W/(W+R+S) X 100%



Terminology 



Work (W) = waktu yang dibebankan kepada seorang operator suatu alat yang dalam kondisi dapat dioperasikan, artinya tidak rusak. Waktu ini meliputi pula tiap hambatan yanga ada, termasuk dalam hambatan tersebut adalah waktu- waktu untuk pulang pergi ke permuka kerja, pindah tempat, pelumasan, dan pengisian bahan bakar, hambatan karena cuaca, dll.







Repair (R) = waktu untuk perbaikan dan waktu yang hilang karena menunggu saat perbaikan termasuk juga waktu untuk penyediaan suku cadang serta waktu untuk perawatan preventif







Standby (S) = standby hours atau jumlah jam suatu alat tidak dapat dipergunakan padahal alat tersebut tidak rusak dan dalam keadaan siap beroperasi







W+R+S = schedule hours



Tugas 



Sebuah Proyek Galian memiliki volume sebesar 242.000 m3 yang bermaterial lempung kering (dry clay), proyek ini menggunakan alat berupa 



2 unit Excavator Komatsu PC 450-7 dengan cycle time 27 detik,







7 unit Truk Komatsu HD 325-6,







dan di bantu oleh 2 unit Dozer Komatsu D85A-21.







Hasil galian akan di timbun ke area yang berjarak 1 km dari daerah galian dengan jalan menurun -5%. Hitunglah berapa lama proyek akan selesai jika diasumsikan jam kerja satu hari adalah 10 jam dan Mechanical Availability adalah 85%.







Untuk spesifikasi alat dan grafik performance silakan lihat di komatsu handbook



Project Profile 



Material dry clay (density 1.6 ton/m3)







Insitu/Bank volume sebesar 242.000 m3







Loose volume =346.060 m3 (LV)







Excavator machine : 2 unit Excavator Komatsu PC 450-7







Hauling unit : 7 unit Truk Komatsu HD 325-6,







Hauling Road Profile 



Distance 1 km







Grade 5%







Mechanical Availibility 85%







Working hours : 10 hours/day







Assumption Working Efficiency : 83%



Excavator Productivity 



Bucket capacity 1.9 – 2.1 m3 (A)







Bucket fill factor 1.2 (B)







Working hours 10 hours/day = 36.000 secs







Cycle time 27 secs







How Many cycle per day = 36000secs/27 secs = 1333 cycle (C)







Mechanical Availibility 85% (D)







Assumption Working Efficiency : 83% (E)







Swelling factor 1.43



Prod Daily= A x B X C X D x E = 2,257 m3/day 2 excavator = 4514 m3/day (EX)



Day requirement = LV/EX = 76.6 day



Truck Productivity 



Truk Komatsu HD 325-6







Capacity 22.8 m3 (36.5 ton)







Weight load = 27.2 ton + 36.5 ton = 63.7 ton







Truck Cycle time 







Loading time



N = (22.8 m3/(2 m3 x 1.2) ) = 9.5 Loading time = 9 x 27 secs= 243 detik (i)







Hauling time (loaded) avg speed 38.5 km/hr 



Dist 1 km = 94 secs travel time (ii)







Dumping time 1.15 min = 69 secs (iii)







Returning time avg speed 50.35 km/hr 







Dist 1 km = 72 secs travel time (iv)



Manuever time = 20 secs (v)



Truck Productivity 



Total cycle time = 243 s + 94 s + 64 s + 72 s + 20 s = 493 secs







How Many cycle per day = 36000secs/493 secs = 73 cycle







Daily Production = Truck Capacity x cycle per day x D x E = 22.8 x 73 x 0.85 x 0.83 = 1174 m3/day per truck 







7 truck = 1174 m3/day x 7 = 8219 m3/day



DAY requirement = 346.060 m3 : 8219 m3/day = 42 Days