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Interactive Audio Lesson
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Cycle Time Components
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Class, today we will discuss the components of cycle time in scrapers. Can anyone tell me what components make up the cycle time?
I think it includes loading and dumping times?
That's correct! Cycle time consists of **Load Time** (LT), **Haul Time** (HT), **Dump Time** (DT), **Return Time** (RT), and others. Remember the acronym LHDRSTTA, which stands for Load, Haul, Dump, Return, Spot, Turn, and Acceleration, Deceleration, Braking Time.
What do we mean by fixed and variable times?
Great question! Fixed time does not depend on distance—like loading and dumping. However, variable time depends on haul and return distances.
The Law of Diminishing Returns
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Let's explore the 'law of diminishing returns' in loading scrapers. Why do you think loading the scraper to its maximum capacity lowers production?
Is it because the material creates resistance once the bowl is nearly full?
Exactly! When the bowl reaches around 85% capacity, other material piles up, causing increased resistance which reduces the loading rate. Always aim for optimizing the load.
But how do we know what's the optimum loading time?
Good question! You must refer to the load growth curve and manufacturer’s data to determine optimal load times. Always draw and analyze the curve!
Maintaining Haul Routes
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Next, let’s touch on maintaining haul routes. Why is that significant?
I think it helps the scraper travel faster?
Absolutely! A well-maintained haul route reduces cycle time by minimizing rolling and grade resistances. Regular maintenance also cuts down operating costs.
So it saves money in the long run as well?
Yes! Investing in haul route maintenance pays off with enhanced productivity and reduced costs.
Back-Track Loading Method
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Now, let’s discuss back-track loading. Can anyone explain what back-track loading involves?
Is it when the pusher helps the scraper load and then moves back after the scraper is full?
Exactly! The pusher detaches once the scraper is loaded and back-tracks to assist another scraper. This method enhances efficiency during loading operations.
Are there risks involved when the scraper turns while loaded?
Yes, turning while loaded can be unsafe. Ideally, the loading should happen before turning for safety protocols.
Optimizing Operations with Pushers
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Finally, let’s wrap up with the advantages of utilizing pushers. How do pushers contribute?
They help reduce the loading time for scrapers.
Right! Each pusher can assist multiple scrapers, thereby enhancing productivity. It's about balancing the operations to minimize waiting time.
What happens if we don't balance the number of pushers and scrapers?
If there's an imbalance, either the pusher will wait for the scraper or vice versa, which greatly affects efficiency. Always ensure you have enough pushers for the scrapers.
Introduction & Overview
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Quick Overview
Standard
The section emphasizes understanding cycle time components in scraper operations, dissecting fixed and variable times, diving deeper into the loading process, specifically focusing on back-track loading, and the implications of optimizing loading techniques.
Detailed
Detailed Summary of Back-Track Loading
This section delves into the cycle time associated with scraper operations, represented by the equation: Cycle Time = LT + HT + DT + RT + ST + TT + ADBT. Here, each variable represents essential elements of scraper function:
- LT: Load Time
- HT: Haul Time
- DT: Dump Time
- RT: Return Time
- ST: Spot Time
- TT: Turn Time
- ADBT: Acceleration, Deceleration, and Braking Time
Cycle time can be split into two categories: fixed time, which includes loading, dumping, and other non-distance dependent actions, and variable time, which is determined by hauling and return distances. The section particularly highlights that while loading time remains relatively consistent, it should be optimized to prevent inefficiencies known as the 'law of diminishing returns.' This includes understanding how the loading growth curve influences productivity based on the loading mechanisms of scrapers.
Furthermore, it emphasizes that the efficient management of haul routes directly affects cycle times and overall productivity of the scraper, focusing on maintenance's economic impact. Lastly, the section discusses the back-track loading method, where a pusher assists the scraper as it loads material.
Audio Book
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Cycle Time Components
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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 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. So, all this manure comes under this ADBT acceleration deceleration and the braking.
Detailed Explanation
The cycle time of a scraper is broken down into several components, each represented by an abbreviation. This includes loading time (LT), hauling time (HT), dumping time (DT), return time (RT), spotting time (ST), turning time (TT), and ADBT which accounts for acceleration, deceleration, and braking. Understanding these components helps in specifying how long the scraper takes to complete its entire operation from loading to returning empty.
Examples & Analogies
Imagine a school bus. The time it takes for the bus to make a full round — from picking up kids, driving to school, dropping them off, returning back, and then parking — can be compared to the cycle time of a scraper. Each step (picking up, driving, dropping off, etc.) takes a certain amount of time that sums up to the total bus round's duration.
Fixed vs Variable Time
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So, basically you can split the cycle time into 2 parts. One is fixed time, 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 how far the scraper travels. In contrast, variable time encompasses hauling and returning, which are heavily dependent on the distance traveled and the speed of the scraper.
Examples & Analogies
Consider baking a cake. The time taken to prepare the batter and bake it is fixed; it won't change regardless of how many cakes you decide to bake. However, if you decide to deliver the cakes to a different location, the time it takes to get there varies based on traffic and distance. Similarly, in a scraper's operation, some tasks (like loading) have a fixed duration, while others (like hauling) may change.
Loading Time Consistency
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So, basically 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 and we are going to supplement the loading power.
Detailed Explanation
The loading time for scrapers remains relatively uniform whether the scraper is large or small. This is largely because scrapers are often assisted by pushers, which help in the loading process. The size of the pusher must correspond to the size of the scraper for effective operation.
Examples & Analogies
Think of a friend helping you carry boxes to a car. Whether it's a small box or a big one, your friend can help out in a similar timeframe. Similarly, a pusher assists scrapers regardless of their size, making the loading process steady and efficient.
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 a production. So, this is what is a common belief this is what is a common assumption, but that is not true.
Detailed Explanation
The load growth curve indicates that loading a scraper to its maximum capacity can actually reduce production. Early loading occurs efficiently, but as the bowl fills (around 85% capacity), resistance increases because the incoming material struggles against what is already in the bowl. This results in a decrease in the rate of loading, illustrating a principle known as the 'law of diminishing returns.'
Examples & Analogies
Imagine trying to stuff too many clothes into a suitcase. At first, you can fit many shirts and pants easily, but as it gets closer to full, you find it increasingly difficult to add more. Each piece you try to add meets resistance from the clothes already there, which is similar to how loading too much material in a scraper decreases efficiency.
Haul and Return Time
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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 times are variable components of the scraper's cycle time. These durations depend on the distance traveled and the speed at which the scraper operates, which can be influenced by project site conditions, such as rolling resistance and grading.
Examples & Analogies
If you're running a race, the time it takes you to complete it will depend on how far the race is and how fast you can run. Similarly, a scraper's haul and return time relies on how far it needs to travel and how quickly it can move based on the terrain.
Dumping Time
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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, which is the duration taken to unload material, is influenced by the size of the scraper and the type of material being dumped. Looser materials can be dumped quickly, while cohesive, sticky materials require more time. Additionally, site constraints, such as congestion, can further affect the dumping process.
Examples & Analogies
Imagine trying to pour sand out of a bag versus trying to pour molasses. Sand (a loose material) flows out quickly, while molasses (a sticky material) takes significantly longer to pour out. This highlights how material characteristics affect dumping times.
Turn Time Considerations
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So, you can see that the turn time is basically not affected by the type or the size of the scraper. So, hope you remember the picture which I have shown to show the production cycle of the scraper, you can see the scraper commonly you can see that 2 turnings are done by the scraper.
Detailed Explanation
Turn time is an important aspect of the scraper's cycle time, and it is generally consistent, regardless of the scraper's type or size. However, turn times can vary depending on the environment, such as whether the turn occurs in a congested area (cut area) or a more open area (fill area), with congestion typically increasing turn durations.
Examples & Analogies
Think of driving a car. Making a wide turn in an open parking lot is quick, but doing the same turn in a crowded space with several obstacles takes much longer. This serves to illustrate how site conditions can influence turn times for scrapers.
Balancing Scrapers and Pushers
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As we discussed earlier when you use a pusher for assisting your scraper, you can reduce the loading time of the scraper, it will help you to increase the productivity of the scraper and reducing unit production cost of the scraper.
Detailed Explanation
Using a pusher to assist scrapers during loading can decrease loading time, thereby enhancing overall productivity and reducing costs. However, it is critical to balance the number of scrapers with pushers to avoid either machine waiting for the other, which would lower operational efficiency and increase costs.
Examples & Analogies
Imagine having a team for a relay race. If one runner gets tired and can't hand off the baton on time, the entire team's performance suffers. Similarly, balancing scrapers and pushers ensures smooth operations, maximizing efficiency and minimizing idle time.
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 time for scraping operations, divided into fixed and variable times.
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Fixed Time: Time elements such as loading which do not depend on distance.
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Variable Time: Number of elements determined by distance, like haul and return.
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Back-Track Loading: Pusher-assisted loading which optimizes time.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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In a well-maintained haul route, travel time for an unloaded scraper can be reduced significantly, which contributes to better productivity.
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The loading growth curve shows that loading a scraper beyond 85% capacity yields diminishing returns, thus reducing efficiency.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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To keep scrapers rolling fine, load and haul in your time!
📖 Fascinating Stories
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Imagine a pusher helping a scraper, once loaded, the pusher backtracks like a helper who finishes a task and moves to support another!
🧠 Other Memory Gems
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Remember 'LHD RSTTA' for understanding cycle time components.
🎯 Super Acronyms
Use 'HARD' to remember Haul, Acceleration, Return, Dump for cycle time aspects.
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 required for a scraper to perform its operation, including load, haul, dump, return, spot, turn, and braking.
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Term: Fixed Time
Definition:
Part of the cycle time that does not depend on the distance travelled.
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Term: Variable Time
Definition:
Part of the cycle time that is dependent on the haul and return distances.
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Term: Law of Diminishing Returns
Definition:
A principle indicating that loading beyond a certain point decreases efficiency due to increased resistance.
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Term: BackTrack Loading
Definition:
A loading method where a pusher assists a scraper during the loading phase and then backtracks to help another scraper.