Question

5.5 A scraper with a 275 hp diesel engine will be used to excavate and haul earth for a highway project. An evaluation of the job-site conditions indicates the scraper will operate 40 min./hr. For this project it is anticipated that the total cycle time will be 20 min. for a round trip. Previous job records show the scraper operated at full power for the 1.5 min. required to fill the bowl of the scraper and at 80% of the rated hp for the balance of the cycle time. Calculate the gallons per hour for fuel consumption of the scraper.

Answer 1

Answer: Fuel consumption per hour of the scrapper is 6 gal/hr

Explanation:

Given that;

Rated power = 275 hP

The scraper will work = 40min per hr

anticipated total cycle time = 20min

Previous Scrapper operated full power for 1.5min at 80% hP

First we find the Engine factor;

filling the bucket =  1.5/20 * 100% = 0.075

rest of cycle = (20-1.5)/20 * 80% =  0.74

so total engine factor = 0.075 + 0.74 = 0.815

now Time factor will be 40/60 = 0.6666 =

therefore operating factor = 0.6666 * 0.815 = 0.543

Now we know that for a diesel engine, a range fuel consumption = 0.04 gal/hP

so

Fuel consumption per hour of the scrapper is;

= 0.543 * 275 * 0.04

= 5.97 = 6 gal/hr