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A short class with Sarah and her students. The other ways are under More.
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Today we're discussing the cycle time of scrapers. Can anyone tell me what components we should consider when calculating cycle time?
Isn't it loading time and dump time?
That's correct! We also need to consider turn-in times and travel times. Remember, cycle time gives us a comprehensive insight into how long a particular operation takes.
Why do we need to calculate these times?
Great question! Understanding these times helps us estimate productivity, which is crucial for project planning. We use the formula: total cycle time = loading time + dumping time + travel times.
What happens if we don’t optimize cycle time?
If we don't optimize, it can lead to inefficiencies, increased costs, and delays. Always remember the acronym 'PDCA' - Plan, Do, Check, Act - for effective management!
To make it stick, can we summarize the key parts?
Certainly! Cycle time is comprised of loading, dumping, and travel times. Optimizing these ensures better efficiency and cost management.
Now let’s discuss the swell factor. Can anyone explain what the swell factor means?
It's the ratio between loose weight and bank weight, right?
Exactly! It's important because it affects how we calculate the actual volume of material to be moved. If the swell factor changes, what might happen?
The volume calculations will be off, right?
Yes, and this can lead to overloading or underutilization of the scrapers, resulting in inefficiencies. A quick way to remember this is 'SV = LW/BW,' where SV is swell volume, LW is loose weight, and BW is bank weight.
Are there conditions that can change the swell factor?
Certainly! Material moisture content and compaction due to pushing are common factors. Remember this—compaction increases the swell factor by about 10% when pushing!
Can we summarize our discussion on the swell factor?
Absolutely! The swell factor is key for volume calculations and it's vital to watch for any conditions that might affect it.
Let's move to calculating total resistance in a haul route. What do we need to consider?
Rolling resistance and grade resistance?
Correct! Rolling resistance is uniform, but grade resistance varies based on the slope. When we calculate it, what units do we use?
Kilograms per ton, and then we can convert it into percentages, right?
Exactly! To find total resistance, we add rolling and grade resistance. Remember our formula for conversions: 1% is equal to 10 kg per ton.
So if we have a +5% grade, that equals 50 kg per ton?
Yes. And vice versa, for a -3% grade, that would mean -30 kg per ton. Always ensure to use the correct values for accurate calculations!
Can we wrap up what we've learned about resistance?
Sure! The total resistance includes both rolling and grade resistance. Always convert grade to kg per ton for consistency.
Now, let's talk about balancing scrapers and pushers. Why is this important?
It minimizes delays during operation?
Exactly! The pusher cycle time is usually smaller. Can anyone tell me how to calculate the balance number of scrapers for one pusher?
Is it the cycle time of the scraper divided by the cycle time of the pusher?
Right! This formula allows us to determine how many scrapers one pusher can efficiently support. So if we get a balanced number of 5.68, what would we do next?
Round it off to either 5 or 6 and calculate productivity?
Exactly! Always assess the implications of rounding up or down. Use real data on productivity to make decisions. Remember 'E = MC^2' - Evaluate, Modify, Choose, and Confirm future operations!
Can we summarize the balancing approach?
Sure! Balancing scrapers and pushers increases productivity and minimizes waiting times. Always do your math and assess real operational metrics!
A comprehensive measurement of time for one complete operation.
An essential measure for volume conversion based on the compaction of materials.
A key factor affecting machine mobility and efficiency.
The impact of slope on the transport of materials during operation.
The relationship between machines which aids in productivity.
For a swell that's at its rest, excavation makes it bulge the best.
Imagine a construction crew trying to build a road. They use scrapers and pushers. If they don’t balance these machines like puzzle pieces, projects could slow down, leading to delays and costs adding up like bricks in a wall.
Remember the acronym SHRINK for swell factor: 'S' for Swell, 'H' for High weight, 'R' for Ratio, 'I' for Input (material), 'N' for Needed calculations, 'K' for Keep in mind the impact!
CRM - Cycle, Resistance, Management - for remembering cycle time, total resistance factors, and ongoing machinery management.
Term
Cycle Time
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Term
Swell Factor
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Term
Rolling Resistance
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Term
Grade Resistance
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The total time taken for a machine to complete a set task including loading, transportation, dumping, and other auxiliary times.
A factor representing the increase in volume of material when it is excavated compared to when it is in its compacted state.
The resistance encountered by a vehicle due to contact with the ground or friction as it moves.
The resistance experienced due to the slope of the terrain during movement.
The percentage time that the machine is actively working compared to the total operational time.
Machines that rely on each other for completing tasks in a coordinated manner, such as scrapers and pushers.
The path or track that earth-moving equipment follows to transport materials.
This section covers cycle time calculations related to scrapers in earth moving operations, including productivity estimation and balancing machinery.
The section discusses the fundamental concepts of cycle time calculations, focusing on scrapers' productivity in earth-moving projects. It elaborates on estimating productivity, understanding key factors such as swell factor, resistance in haul routes, and the importance of balancing scrapers and pushers in improving efficiency.
In this section, we delve into cycle time calculations crucial in determining the productivity of scrapers used in earthmoving operations. The productivity of scrapers is influenced by factors such as initial material conditions (e.g., swell factor), rolling resistance, and the dynamics of interdependent machinery like scrapers and pushers. We will methodically outline how to calculate the cycle time by estimating loading, hauling, and dumping times, as well as accounting for machine efficiency.