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Today, let's start with an important concept in scraper productivity: the swell factor. Can anyone tell me what the swell factor represents in earthmoving?
Isn’t it the ratio of the loose volume of material to its bank volume?
Exactly, Student_1! The swell factor helps us understand how much a given volume of material expands when it becomes loose. Now, what happens to the swell factor when we have push-loaded scrapers?
I think it increases by 10% because of compaction, right?
Spot on! This compaction is crucial when estimating the weight of the load in the scraper. Remember, for push-loaded scrapers, we always need to account for this increase. Let's recap: the swell factor helps gauge material volume changes, especially under additional pressure from pushers.
Now, let's talk about the various time components in a scraper's cycle. Who remembers the average loading time for a scraper?
It's 0.8 minutes, right?
Correct! And how about dumping time?
That should be 0.37 minutes for a typical scraper.
Nice work! So far, we know the loading and dumping times. Can someone remind me how we calculate the total cycle time?
We add all specific activity times together, right?
Exactly! And now, let’s remember that the cycle time for scrapers must also consider travel times depending on haul route characteristics.
In earthmoving operations, resistance plays a key role in estimating productivity. Can someone tell me what types of resistance we consider?
We look at rolling resistance and grade resistance!
Correct! Rolling resistance is constant, while grade resistance can vary based on the slope of the haul route. Can anyone tell me how we can express these resistances?
They can be expressed in kg per ton or as a percentage gradient!
Exactly, Student_3! Knowing these helps us apply them to calculate the total resistance that affects our scraper's speed. Let’s summarize: resistance factors are critical in estimating effective travel speeds on different haul segments.
Finally, let's discuss balancing the number of scrapers to pushers. Why is this balance important?
It helps reduce the waiting time for machines, right?
Precisely! We want to ensure that one pusher can serve multiple scrapers effectively. Alright, if our scraper cycle is 7.78 minutes and the pusher cycle is shorter, how do we find the number of scrapers per pusher?
We divide the scraper cycle time by the pusher cycle time!
Excellent work! This ratio gives us insights into optimizing our resources. To recap, finding the right balance between scrapers and pushers can significantly enhance productivity.
Indicates how material volume changes from bank to loose state, essential for estimating weights.
Comprises loading, traveling, and unloading durations, critical for productivity assessments.
Affects the speed and efficiency of earthmoving operations, derived from the haul route conditions.
A key factor based on the slope of the route, influences the effective load on the machinery.
Total operational weight of the scraper, crucial for calculating resistance and efficiency.
To know the swell, just give it a yell, from bank to loose, it tells the true use.
Imagine a fat cat named Swell who loves to play in the dirt. When he digs into the soil, it spreads out, just like when we handle materials, turning from bank to loose, and that's the swell factor!
Remember the acronym SCRAPE for Speed (travel), Cycle time, Resistance, Average load, Pusher impact, and Efficiency.
CYCLE for Cycle time: Components, Yield, Capacity, Load time, Efficiency.
Term
What is the swell factor?
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Term
How is cycle time determined?
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The ratio of loose dry unit weight to bank dry unit weight, indicating how volume changes when material is disturbed.
The total time taken by a machine to complete one full cycle of operation, including loading, hauling, and unloading.
The resistance encountered when a vehicle moves over a surface, which impacts its speed and efficiency.
The resistance due to the slope of the haul route, influencing the power needed for movement.
The total weight of a machine, including its empty weight and the weight of the load it carries.
This section focuses on productivity estimation for scrapers in construction, detailing cycle times, resistance on haul routes, and optimizing the number of scrapers and pushers.
In this section, the process of estimating the productivity of scrapers and the interaction between scrapers and pushers is examined. Details on material properties, cycle times for various activities, and the impact of gradient and resistance on productivity are provided. The section concludes with methods for balancing the number of scrapers with pushers to optimize performance.
In this section, we delve into the productivity estimation of scrapers used in earthmoving operations. The discussion begins with an introduction to scrapers, focusing on their operation in moving dry earth soil with specific unit weights and swell factors. Key concepts such as the swell factor—defined as the ratio of loose dry unit weight of material to its bank dry unit weight—are introduced, including adjustments for pusher loading which increases the swell factor by 10%.
We explore the various cycle elements of scraper operation, including average loading and dumping times, as well as turn times in both the fill and cut areas. Resistance factors on haul routes are analyzed, along with the importance of breaking down the haul distance into manageable segments based on gradient.
The segmental analysis covers different gradients experienced during operation, providing a detailed understanding of how rolling resistance and grade resistance impact overall productivity. A systematic approach to estimating travel times and costs leads to methods for balancing the number of scrapers and pushers in operation, ensuring an efficient workflow. The productivity calculations culminate in determining the unit cost of production, essential for effective project management in construction.