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Interactive Audio Lesson
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Understanding Cycle Time
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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.
Loading Time and Growth Curve
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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.
Hauling and Returning
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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.
Dump Time and Its Factors
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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!
Pusher's Role and Balancing Operations
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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.
Introduction & Overview
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Quick Overview
Standard
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.
Detailed
Detailed Summary
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.
Audio Book
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Understanding Cycle Time
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Cycle time = LT + HT + DT + RT + ST + TT + ADBT
(Where, LT-Load, HT-Haul, DT-dump, RT-Return, ST-Spot, TT-Turn, ADBT- Acceleration, Deceleration and braking)
So, cycle time of a scraper, it is nothing but load time, hauling time, dumping time, return time spotting because most of the conventional scrapers have a pusher loader scraper. So, it has to spot the pusher, that spotting time is also included then turning, then ADBT that means the time needed for increasing your speed or decreasing the speed, time needed for applying the brakes.
Detailed Explanation
Cycle time is the total time it takes for a scraper to perform its job, which includes several components: loading (LT), hauling (HT), dumping (DT), returning (RT), spotting (ST), turning (TT), and acceleration, deceleration, and braking time (ADBT). Each of these components is crucial in determining how long it takes for the scraper to complete one full cycle of operation, from loading to dumping back to loading again.
Examples & Analogies
Think of a bakery that makes a batch of cookies. The cycle time for baking involves several steps: preparing (loading), baking (hauling), cooling (dumping), cleaning the baking trays (returning), resetting the oven (spotting), and the time it takes to make adjustments (turning and ADBT). If any step takes too long, the entire batch is delayed, just like a scraper.
Fixed vs Variable Time
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So, basically you can split the cycle time into 2 parts. One is fixed time, the other one is variable time. Fixed in the sense this part of the cycle time does not depend upon your travel distance. So, that is called as fixed time, say your loading, dumping, turning, your accelerating, decelerating. All these things comes under the fixed time. So, it is not dependent upon the distance travelled. The other one is a variable time, your haul and return is a variable time because it is significantly dependent on your travel distance.
Detailed Explanation
Cycle time can be categorized into fixed time and variable time. Fixed time includes components like loading, dumping, and turning, which remain constant regardless of distance traveled. In contrast, variable time depends on aspects like how far the scraper has to travel and the speed at which it moves, which can change based on different conditions on site.
Examples & Analogies
Imagine a road trip. The time spent preparing the car (e.g., filling gas, packing) is the fixed time; it doesn't matter how far you drive. The driving time, however, varies based on distance and speed. If you take a scenic route (long-distance), it could take longer compared to taking the highway (short-distance) to the destination.
Significance of Loading Time
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So, the loading time of the scraper is fairly consistent irrespective of the scraper size. So, that means whether it is going to be a smaller scraper or bigger scraper in both cases. So, commonly we can say that we are going to assist this scraper with the help of a pusher according to the size of the scraper the compatible size of the pusher you have to select.
Detailed Explanation
Loading time for scrapers tends to remain constant, regardless of the size of the scraper being used. This is because, regardless of size, scrapers often rely on pushers to assist with the loading process. This compatibility between scrapers and pushers is critical in minimizing loading time and enhancing efficiency.
Examples & Analogies
Consider how a large truck and a small truck might fill up at a gas station. The time it takes to fill the gas tank—loading time—remains fairly similar regardless of truck size. However, having the right size fuel pump (the pusher) can make the process smoother and quicker.
Load Growth Curve
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Another important concept which we need to know is about the load growth curve for scraper loading. So, we commonly believed that when we load this scraper when we fill the bowl of the scraper to the maximum capacity we are going to maximize production. So, this is what is a common belief this is what is a common assumption, but that is not true. So, people have done the studies and they proved that when we tried to load the scraper to its fullest capacity. So, the production starts reducing beyond a particular time...
Detailed Explanation
The load growth curve illustrates that loading a scraper to its maximum capacity does not always yield the best production rates. As the bowl fills (around 80-85% capacity), resistance increases from the material that is already present, which can hinder the loading efficiency and actually slow down production. Therefore, it's vital to find an optimal loading capacity to maintain efficiency.
Examples & Analogies
Think of a container being filled with water. Initially, water flows in quickly, but as the container gets close to full, the flow slows down because the space for additional water decreases. If you keep trying to pour more past its limit, it spills out instead of filling more efficiently.
Haul and Return Time
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So, the next important component of the cycle time of the scraper is your haul and return time, as I told you it is a variable time, it is going to depend upon your travel distance and the speed of your machine...
Detailed Explanation
Haul and return time is a critical variable component of cycle time. This time is affected by the distance the scraper must travel and the speed at which it operates. Some conditions can speed up or slow down this process, and maintenance of the haul route is essential for reducing resistance and ensuring efficiency in travel times.
Examples & Analogies
Consider a delivery driver. The time it takes for the driver to travel to deliver a package (haul) or return to the starting point (return) varies based on distance and traffic conditions. Keeping the roads well-maintained would be akin to having clear and fast routes for the driver to navigate.
Dump Time Considerations
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So, the next important thing which we are going to see as a component of your cycle time is your dump time. So, your dump time of your scraper it depends upon your scraper size obviously, bigger the scraper your dumping time will be more...
Detailed Explanation
Dump time can be influenced by several factors including the size of the scraper and the type of material being dumped. Loose materials are easier to dump compared to cohesive materials. Furthermore, dump area constraints, like congestion from other machines, can also delay the dumping process.
Examples & Analogies
Imagine dumping sand from a truck into a pile. A small truck might empty easily without any issues, while a large truck might struggle if the site is crowded or if the sand is compacted. Hence, operational efficiency at the dumping location is vital for timely completion.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: The total time from loading to unloading in scraper operations.
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Fixed Time: Components of cycle time unaffected by travel distance.
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Variable Time: Components of cycle time that depend on distance and speed.
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Load Growth Curve: Illustrates how loading efficiency decreases beyond a certain point.
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Haul Route: The path maintained for efficient material transport.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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The loading time for a pusher-loaded scraper in common earth is approximately 0.8 minutes.
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If the scraper is overloaded beyond 85%, the loading rate decreases due to resistance, illustrating diminishing returns.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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For scrapers, cycle's seen, loading, hauling, and dumping clean.
📖 Fascinating Stories
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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!
🧠 Other Memory Gems
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Remember 'LHDR' for Cycle Time: Load, Haul, Dump, Return.
🎯 Super Acronyms
‘SHARPS’ for cycle time
- Scraper
- Haul
- ADBT
- Return
- Pusher
- Spotting.
Flash Cards
Review key concepts with flashcards.
Glossary of Terms
Review the Definitions for terms.
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Term: Cycle Time
Definition:
The total time taken by a scraper to complete its operations, including loading, hauling, dumping, returning, spotting, turning, and acceleration/deceleration.
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Term: Fixed Time
Definition:
Part of the cycle time that does not depend on travel distance, including loading, dumping, and turning times.
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Term: Variable Time
Definition:
Part of cycle time that is dependent on factors like distance traveled and speed.
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Term: Load Growth Curve
Definition:
Graphical representation showing the relationship between loading time and payload percentage, illustrating the diminishing returns of overloading.
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Term: Haul Route
Definition:
The designated path taken by the hauling equipment to transport materials, which requires maintenance for efficiency.
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Term: Dump Time
Definition:
The time it takes for a scraper to unload its materials at the dumping site, influenced by material type and site conditions.
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Term: Pusher Loader
Definition:
A type of loader that assists scrapers in the loading phase, reducing their loading times.