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Interactive Audio Lesson
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Introduction to Scraper and Pusher Operations
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Welcome, everyone! Today we will delve into the balancing of scraper and pusher operations. Can anyone tell me why it's essential to balance these operations?
Is it to ensure that one machine doesn't wait for the other?
Exactly! The efficiency of one relies on the other, especially during the loading phase. This way, we can minimize idle time and maximize productivity.
What determines when a scraper needs the pusher?
Great question! The scraper primarily requires assistive help during loading. Once the scraper bowl is full, it can operate independently.
So, how do we calculate how many scrapers one pusher can serve?
We use the cycle time of the scraper divided by the cycle time of the pusher. Let's remember the acronym BUMP, for 'Balancing Using Machine Performance'!
BUMP? I like that! It makes it easier to remember.
Understanding Cycle Times
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Now, let’s break down the cycle times. The scraper cycle time is impacted by loading, dumping, and travel time. Does anyone remember the components?
I think it includes average loading time and average dumping time?
Yes! Also, the turn time and any time spent moving in the cut area. Remember the mnemonic 'LOAD', which stands for Loading, Output, and Dumptime!
What about the pusher cycle time?
The pusher cycle time is generally shorter and calculated using specific formulas. We should always consider variations based on operational conditions.
Balancing Machines for Maximum Productivity
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To optimize productivity, we must determine the balanced number of scrapers per pusher. What happens when we have too many scrapers?
The scrapers might have to wait for the pusher, creating delays.
Exactly! Conversely, not having enough scrapers means the pusher's work goes to waste. We can calculate the balance using the formula: N = Ts / Tp, where Ts is the scraper cycle time and Tp is the pusher cycle time.
And if we get 5.68, do we round down or up?
Good detail! We can either round down to 5 or round up to 6, but we must assess productivity implications in both cases.
Economic Factors in Scraper-Pusher Operations
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Let’s now talk about the economic side of operations. Why would we want to compare the productivity of using 5 or 6 scrapers?
To see which setup minimizes costs while maximizing efficiency?
Exactly! Conducting an economic analysis assists us in making informed decisions. Remember the acronym TRAC - Total Return on Asset Considerations!
TRAC makes it memorable too! Sounds like a strategy.
Can we always find that optimal number?
Not always, as it varies by project. Continuous evaluation is key to achieving balance and optimal productivity.
Introduction & Overview
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Quick Overview
Standard
The section discusses the detailed relationship and cycle times between scrapers and pushers, emphasizing the need for balancing their operations. Key concepts include the estimation of cycle times, the interdependency of machines, and strategies for maximizing efficiency through balanced operations.
Detailed
In this section, we explore the intricate relationship between scrapers and pushers in earth-moving projects. It begins with an explanation of the cycle times for both machines and highlights the need for balance due to their interdependence during loading phases. The balanced number of scrapers per pusher is crucial for minimizing waiting time and maximizing productivity. We derive the formula for calculating the number of scrapers served by a single pusher and examine the factors affecting cycle times, such as loading, dumping, and travel times. The section concludes by discussing the economic implications of choosing between different numbers of scrapers to achieve optimal operation levels. Balancing these operations is essential for increasing effectiveness, reducing costs, and ensuring streamlined workflow.
Audio Book
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Introduction to Balancing Operations
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So, now let us work on the first problem on productivity estimation of the scraper. So, a scraper with the assistance of the pusher is moving the dry earth soil having unit weight of 1660 kg per bank meter cube.
Detailed Explanation
In this section, we are discussing the operation of scrapers and pushers in earth-moving projects. Scrapers are heavy machinery used to collect and haul materials like soil. When they work with pushers, they can move larger quantities of material efficiently. The unit weight of the dry earth soil being moved by the scraper is mentioned as 1660 kg per bank meter cube, which helps estimate the load and productivity. This figure is significant because it influences the calculations for the load the scraper can carry and the overall efficiency. Understanding the relationship between scrapers and pushers lays the foundation for estimating productivity in construction operations.
Examples & Analogies
Think of scrapers as trucks carrying goods, while pushers are like loaders that help load more goods onto these trucks. Just like how the weight of the goods affects how much the truck can carry and how efficiently it can drive, knowing the weight of the soil helps in calculating how much the scraper can effectively move on a construction site.
Understanding Swell Factor
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So, hope you remember what is swell factor? We have defined what is swell factor in early lecture, it is a ratio of loose dry unit weight of the material by bank dry unit weight of the material. So, particularly for the push loaded scrapers your swell factor, the unit weight will increase by 10%, because of the additional pressure which we received from the pusher to the material inside the bowl.
Detailed Explanation
The swell factor is crucial in understanding material volume during excavation and hauling. It quantifies how much the volume of material increases once it is disturbed or loosened, typically from being compacted in the ground. For push-loaded scrapers, this factor increases by about 10% due to the additional pressure applied by the pusher. This means when a pusher applies force, more material can be packed into the scraper bowl, increasing its effective weight and density, which is vital for calculations regarding load and efficiency.
Examples & Analogies
Imagine trying to fit as many marbles as possible into a jar. When the marbles are packed tightly together (bank), you can fit a certain number. However, if you shake the jar (disturb the soil), the marbles spread out, and you can fit in more (loose volume). Now, if a friend helps you pack the marbles in tightly (similar to a pusher), you can fit even more than before because of that added pressure.
Calculating Gross Weight and Resistance
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So, now the next step is we have to determine what are all the resistance in the haul route? The rolling resistance is uniform throughout the haul route. Is given in the question is 50 kg per ton or equivalent gradient as 5%.
Detailed Explanation
To ensure the scraper operates efficiently, it's essential to calculate the total resistance encountered during operation. Rolling resistance refers to the force resisting the motion of a vehicle on a surface. In this scenario, it is given as 50 kg per ton, or a 5% equivalent gradient, indicating the slope the scraper must overcome while hauling materials. Both rolling resistance and grade resistance (which changes according to the slope of the haul route) are crucial for calculating the speed and power requirements of the scraper.
Examples & Analogies
Imagine pushing a shopping cart up a slight hill. The effort it takes to push the cart forward while going up represents rolling resistance. If the hill gets steeper, it becomes even harder to push, showing how gradient affects force. Similarly, knowing the resistance helps engineers ensure the scraper can handle what’s being carried without unnecessary strain.
Balancing Scraper and Pusher Numbers
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Now let us see the balanced number of scrapers which are served by one pusher. So, that is equal to n is nothing but number of scrapers served by one pusher. It is equal to cycle time of the scraper by cycle time of the pusher.
Detailed Explanation
Balancing the number of scrapers and pushers ensures smooth operation and minimizes delays in material handling. Each machine has a cycle time, which is the total time taken to complete a loading, hauling, and dumping cycle. By calculating the ratio of the scraper’s cycle time to the pusher’s cycle time, we can determine how many scrapers one pusher can effectively assist without causing downtime. In this case, the cycle times were previously calculated as 7.78 minutes for the scraper and 1.37 minutes for the pusher, leading to a balanced number of approximately 5.68 scrapers.
Examples & Analogies
Think of a restaurant where a waiter serves multiple tables. If the waiter can serve each table in 5 minutes (equating to the scraper) but takes only 1 minute to refill drinks at another table (equating to the pusher), we can determine how many tables the waiter can handle at any given time. Efficiently balancing these operations ensures that customers (in this case, the scrapers) are served quickly without waiting too long.
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 required to complete one full cycle of scraper and pusher operations.
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Interdependency: Refers to how scrapers and pushers depend on each other for efficient operation during loading.
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Balancing Operations: The act of determining the optimal number of scrapers and pushers based on their cycle times.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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If a scraper takes 7.78 minutes per cycle and a pusher takes 1.37 minutes, approximately 5 to 6 scrapers can be efficiently managed by a single pusher.
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In a scenario where the loading time of a scraper impacts the efficiency, reducing that time can significantly help in balancing operations.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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To balance scrapers and pushers alike, avoid idle waits and keep the cycle tight.
📖 Fascinating Stories
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Imagine a construction site where scrapers are waiting for pushers to load material. When balanced, scrapers efficiently fill their bowls while pushers assist seamlessly, creating a workflow rhythm like dancers.
🧠 Other Memory Gems
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Remember RICS: 'Reduced Idle, Continuous Scraping' for balancing machines effectively.
🎯 Super Acronyms
BUMP
- Balancing Using Machine Performance—use this to remember what to consider when optimizing scraper and pusher operations.
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 to complete one cycle of operation, including all phases from loading to unloading.
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Term: Scraper
Definition:
A type of earth-moving equipment used to load and transport bulk materials.
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Term: Pusher
Definition:
A tractor used to assist scrapers, helping to push material and reduce loading time.
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Term: Balance
Definition:
A state of optimal operation where the number of scrapers and pushers minimizes idle time.
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Term: Swell Factor
Definition:
A measure of the expansion of material from its bank volume to loose volume, crucial in calculating load capacities.