Ms Cassandra Essay

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Waste Collection Exercises

Problem 1: Description
Determine the number of hauled container trucks required to serve a shopping center producing 113 yd3 of waste per day. Containers are picked up daily and are 9 yd3 each and are 70% full. Use the data on the following slide. Use this equation: Y = a + b + c(d) + e + f +g

Data
Total collection time (Y): 8 hours Off route time (f + g): 1.6 hours Time to drive to and from the garage (a + e): 30 min Time to drive to and from disposal facility (round trip): 12 minutes Time to unload at the disposal facility: 11 min Time to pick up container: 5 min Time to unload container: 5 min Time to drive between containers: 4 min

Question
What are the number of trips to the disposal site per day required vs. the number of trips per day each truck can make? Note: Number of trips/day [c] required is equal to the number of containers.

Step 1: Solve for c, number of trips possible per day per truck
Equation: Y = a + b + c(d) + e + f +g b is a function of which variables? Answer is given in next slides

Step 1: Solve for c
Y = a + b + c(d) + e + f +g a + e = 30 min b = (pick up + put down) x c + drive between time x (c-1) b = 14 c – 4 d = drive to disposal site + time at site d = 11 + 12 f + g = 1.6 (60)

Step 1: Cont’d
480 = 30 + 14c – 4 + 23c + 96 c = 9.7 c ~ 9 trips/day possible

Step 2: Calculate the number of containers filled per day
The number of containers that must be delivered to the disposal site per day is equal to the number of trips required per day Think about the relationships among the given data to make this calculation Answer is given in next slide

Step 2: Calculate the number of containers filled per day
Daily Volume 113 yd3 /d = Container Volume x Utilization 9 yd3 /container x 0.7
= 17.9 containers/day = 18 trips/day But 9 trips/day are possible So 2 trucks must be used

Problem 2: Description
Calculate the truck volume (v) and the number of trucks (N) you would recommend to serve a residential community using a manually loaded compactor on a weekly basis. Each location is served once each week. Use data from the following slide.

Data
Total number of locations = 50,000 loc/week Waste generation per location = 20 lb/loc Waste specific weight = 177 lb/yd3 Compaction ratio = 2.5 Collection time = 1 min/location Total collection time = 40 hrs per week, 5 days/wk Disposal time (total) = 31 min/trip Time to and from garage (total) = 20 min/day Off route time = 15% of total collection time Number of trips/day possible = 2

Step 1: Calculate time required per week as a function of N
Use this equation: Y = a + b + c(d) + e + f +g b is a function of the number of locations each truck visits times the collection time per location Answer is given in next slide

Step 1: Calculate N using time per week for each truck
Y = a + b + c(d) + e + f +g Y = (40)(60) min/wk = 2400 min/wk/truck a + e = 5 x 20 min/wk = 100 min/wk/truck b = no. loc /wk x time/loc b = 50,000 x 1 min/week/N trucks c = 2 trips/day x 5 days/week/truck d = 31 min/trip/truck f + g = 2400 x 0.15 = 360min/wk/truck

Step 2: Solve for N
Answer is given in next slide

Step 2: Solve for N
Y = a + b + c(d) + e + f +g 2400 = 100 + 2 (31)(5) + 360 + 50,000/N N = 31 trucks needed

Step 3: Calculate minimum truck volume required
Truck volume is equal to volume/trip Calculate the required volume/trip

Step 3: Calculate minimum truck volume required
Vol/trip = vol/wk / trips/week
(50,000loc / wk )(20lb / loc) (v)(2.5) = (177lb / yd 3 )(10trips / wk / truck )(31trucks)

v = 7.3 yd3 v ~ 10 yd3

Problem 3
A community of 1000 homes stores their waste containers along alleys located in back of all of their homes. A satellite vehicle with a 2-yd3 capacity picks up the waste once per week and delivers it to a mechanically loaded compactor truck that moves along a main artery as the satellite vehicle collects wastes. Calculate the number of trips per week the satellite…