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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 going to explore cycle time, which is a critical measurement for scrapers. Can anyone tell me what they think cycle time refers to?
Is it the total time it takes for the scraper to complete its operations?
Exactly! The cycle time includes several components: loading, hauling, dumping, returning, spotting, turning, and ADBT. Anyone remember what ADBT stands for?
Acceleration, Deceleration, and Braking Time.
Well done! ADBT is crucial because it helps understand the delays caused during speed adjustments. Let’s move on to fixed and variable time components.
What’s fixed time?
That’s when the times are not affected by distance traveled, like loading and dumping. Variable time, on the other hand, depends on the haul distance and speed.
So if the travel distance increases, the variable time increases too?
Exactly! Let's summarize: cycle time is influenced by several factors, including fixed and variable components.
Shifting gears, let’s discuss loading time. How do you think the size of the scraper impacts loading time?
I think larger scrapers would take longer to load.
Actually, it often remains quite consistent, especially when using a pusher loader. The average loading time for a pusher-loaded scraper in common earth is around 0.8 minutes. But remember the load growth curve. What happens if we overfill a scraper?
The loading rate decreases due to resistance.
Right! This leads to the law of diminishing returns. It's better to avoid maxing out the scraper to maintain efficiency.
How do we find that optimum point then?
Good question! By plotting the load growth curve, we can identify the ideal loading time for the specific scraper and material.
Let's focus on the hauling aspect now. What can influence haul and return times?
The distance to travel, and the speed of the machine?
Correct! Different conditions, like terrain and maintenance of the haul route, significantly impact these times. Anyone know why maintaining the haul route is beneficial?
Because a good haul route reduces resistance and makes speeds higher?
Absolutely! By maintaining a smooth route, you also enhance the productivity of your machinery and decrease maintenance costs.
So, it saves money in the long run?
Exactly! So remember, investing in a good haul route pays off through efficiency.
We’ve covered loading and hauling; now, let’s talk about dumping time. What influences how long it takes to dump?
The size of the scraper and the material type?
Correct! Bigger scrapers generally take longer to dump, and loose materials are easier to handle. What else could cause delays at the dump site?
If there are other machines around, it might get congested?
Exactly! Conditions at the dumping site can significantly affect efficiency. Good job identifying those factors!
Finally, let’s discuss pusher tractors. What role do they play during the scraper's cycle?
They help load the scrapers faster?
Correct! Keeping a balanced number of scrapers and pushers is vital, or else one might idle while waiting for the other. How does waiting affect productivity?
If they wait too long, the overall production slows down.
Exactly! Thus managing their numbers ensures optimal efficiency. Summary: we need to be intentional about how many machines are in use to maximize production.
The total time from loading to unloading in scraper operations.
Components of cycle time unaffected by travel distance.
Components of cycle time that depend on distance and speed.
Illustrates how loading efficiency decreases beyond a certain point.
The path maintained for efficient material transport.
For scrapers, cycle's seen, loading, hauling, and dumping clean.
Imagine a busy construction site where scrapers race against time; they need to load quickly, but if they overfill, they slow down. It's a race between efficiency and resistance!
Remember 'LHDR' for Cycle Time: Load, Haul, Dump, Return.
‘SHARPS’ for cycle time: Scraper, Haul, ADBT, Return, Pusher, Spotting.
Term
Cycle Time
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Term
Load Growth Curve
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Term
Pusher Loader
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The total time taken by a scraper to complete its operations, including loading, hauling, dumping, returning, spotting, turning, and acceleration/deceleration.
Part of the cycle time that does not depend on travel distance, including loading, dumping, and turning times.
Part of cycle time that is dependent on factors like distance traveled and speed.
Graphical representation showing the relationship between loading time and payload percentage, illustrating the diminishing returns of overloading.
The designated path taken by the hauling equipment to transport materials, which requires maintenance for efficiency.
The time it takes for a scraper to unload its materials at the dumping site, influenced by material type and site conditions.
A type of loader that assists scrapers in the loading phase, reducing their loading times.
This section elaborates on the various components that determine the cycle time of a scraper, including fixed and variable times, focusing on loading dynamics and the importance of optimizing loading practices.
The shuttle loading section discusses the cycle time of scrapers, highlighting the breakdown into fixed and variable components. It emphasizes the significance of understanding loading times, advancing the loading curve concept, and maintaining haul routes to improve efficiency and reduce costs.
The cycle time of a scraper is vital for optimizing earthmoving operations and involves several components including Load Time (LT), Haul Time (HT), Dump Time (DT), Return Time (RT), Spot Time (ST), Turn Time (TT), and Acceleration/Deceleration/Braking Time (ADBT). This can be categorized into fixed times, which do not depend on travel distance and include loading, dumping, and turning, and variable times, which do depend on distance and speed such as hauling and returning.
Loading Time: The loading time remains relatively consistent irrespective of the scraper size, especially when assisted by a compatible pusher loader. For example, the average loading time for a pusher-loaded scraper is approximately 0.8 minutes in common earth.
Load Growth Curve: It’s important not to load the scraper to maximum capacity due to the law of diminishing returns; this means that filling the scraper beyond 85% reduces the rate of production due to increased resistance from already loaded material.
Haul and Return Time: Their times vary based on distance and speed, which is influenced by project conditions like rolling and grade resistance. Therefore, maintaining the haul route is economically beneficial for reducing cycle time, improving speed, and increasing productivity.
Dump Time: This depends on scraper size, the material being handled, and site constraints. For optimal performance, scrapers are designed for loose materials, and pre-treatments, like soil ripping, can increase their efficiency.
Finally, the section discusses the cycle time of pusher tractors and emphasizes the importance of balancing the number of scrapers and pushers to minimize waiting time, thus optimizing work efficiency.