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Understanding Cycle Time
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Today we're discussing the cycle time of a scraper. Can anyone tell me what components make up this cycle?
Is it just loading and dumping time?
Good start! The full equation is Cycle time = LT + HT + DT + RT + ST + TT + ADBT, where each letter stands for a specific type of time. Can anyone break down what LT stands for?
LT is Load Time, right?
Correct! LT represents how long it takes to load the scraper. Now, why is this time fairly consistent across different scraper sizes?
Because they often use a pusher, so the load time doesn’t change much?
Exactly! The pusher helps optimize this process. One helpful way to remember the components is through the acronym ADBT - Acceleration, Deceleration, Braking Time. Let's keep this in mind as we go on.
Okay, can anyone summarize what we just discussed?
We learned that the cycle time includes various components and that LT is influenced by using a pusher.
Great summary! It’s important to understand how each part plays into the whole cycle time.
Variable and Fixed Time Components
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Let's delve deeper into fixed vs. variable time components. Who can explain what fixed time includes?
Things like loading, dumping, and turning time?
That's right! And can someone tell me what defines variable time?
Variable time depends on travel distance and machine speed?
Exactly! Haul and return times fall under this category. What factors can affect machine speed?
Project conditions like rolling resistance and grade resistance.
Perfect! Let’s remember that maintaining the haul route is key to reducing cycle time. Can anyone think of why?
Because a well-maintained route helps with speed and reduces wear on the machine.
Great observation! This sum up how both components impact our overall cycle time.
Loading Time and the Load Growth Curve
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Now, let’s talk about loading time and the load growth curve. What happens if we try to overfill a scraper?
It actually reduces the loading rate because of resistance?
Exactly! This principle is called the law of diminishing returns. Can someone explain the optimal loading time concept?
It’s the best loading time to maximize efficiency, not just filling it to the max capacity.
Right! We want to optimize our loading strategy. Closing this session, how can we gather this data?
From either the load growth curve or directly from manufacturers.
Exactly! Very well summarized.
Introduction & Overview
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Quick Overview
Standard
The cycle time of a scraper is the total time taken for a complete working cycle and is composed of both fixed and variable time components. Fixed times include loading, dumping, and turning times, while variable times are heavily influenced by the travel distance and the machine’s speed. Optimizing these times is crucial for enhancing productivity.
Detailed
Cycle Time of a Scraper
The cycle time of a scraper can be expressed as:
Cycle time = LT + HT + DT + RT + ST + TT + ADBT
(Where: LT - Load Time, HT - Haul Time, DT - Dump Time, RT - Return Time, ST - Spot Time, TT - Turn Time, ADBT - Acceleration, Deceleration, and Braking Time)
This section thoroughly explores each component contributing to the scraper's cycle time, which can be categorized into fixed and variable times. Fixed times, such as loading, dumping, turning, acceleration, deceleration, and braking, do not depend on the travel distance. In contrast, haul and return times vary based on travel distance and the speed of the machine, which is influenced by site conditions, such as rolling resistance and grade resistance.
Load Time
Loading time for scrapers is consistently efficient across different sizes, largely due to the assistance of a pusher. Manufacturing data indicates that an average load time for a pusher-loaded scraper in common earth is around 0.8 minutes.
However, it’s important to consider the load growth curve which shows that excessively loading the scraper beyond 85% of its capacity can decrease productivity due to material resistance during loading, an effect referred to as the law of diminishing returns. The optimal loading time should be derived from the load growth curve or manufacturer specifications.
Haul and Return Time
This component depends on the speed and distance traveled. Proper maintenance of the haul route can lead to improved productivity by reducing cycle time and unit production costs, highlighting the importance of effective route management.
Dump Time
Dump time is influenced by the scraper size and the type of material being handled. Effective loading techniques can ensure maximum efficiency, particularly when dealing with cohesive materials.
Turn Time
The average turn time varies between the filling area and the cutting area. The increase in congestion in the cut area can lead to higher turn times compared to the fill area.
Understanding and optimizing the cycle time of both scrapers and pushers are essential for enhancing performance in earthmoving projects.
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Understanding 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 are pusher loader scrapers. 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 your speed, time needed for applying the brakes. So, all this manure comes under this ADBT acceleration deceleration and the braking.
Detailed Explanation
Cycle time is the total time it takes for a scraper to complete one full cycle of operations. It includes all essential stages: loading (LT), hauling (HT), dumping (DT), returning (RT), spotting (ST), turning (TT), and ADBT—which stands for acceleration, deceleration, and braking. Each of these terms represents a critical phase in the operation of a scraper, and together they contribute to the overall efficiency and productivity of the machine in a construction or earth-moving project.
Examples & Analogies
Imagine a delivery truck making a round trip to deliver goods. The total time for loading the truck, driving to the destination, unloading, returning to the depot, and preparing for the next delivery is analogous to the cycle time of a scraper.
Fixed vs. Variable Cycle 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 come under the fixed time. So, it is not dependent upon the distance traveled. 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 is divided into fixed and variable components. Fixed time consists of tasks like loading, dumping, and turning that do not change with the distance traveled. In contrast, variable time changes based on how far the scraper travels, particularly during the hauling and returning phases. This distinction is important as it allows operators to plan operations based on predictable tasks versus those that vary with conditions.
Examples & Analogies
Consider a car trip. The time spent getting ready (fixed time) doesn't change regardless of how far you drive. However, the driving time (variable time) increases as the distance to your destination grows. In the context of the scraper, this means fixed tasks can be planned more easily than variable tasks.
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
Loading time is relatively stable no matter the size of the scraper because a larger scraper will need a larger pusher to assist with loading. This compatibility ensures that the loading duration remains consistent, which is advantageous for project timelines. It is important to consult manufacturers for accurate loading times specific to the scraper model and materials being transported.
Examples & Analogies
Think of loading grocery bags in different sizes of shopping carts. Regardless of whether you have a small or large cart, the time it takes to fill it doesn't vary significantly because you're using the same method to load. Similarly, scrapers, regardless of size, have consistent loading times.
Load Growth Curve and Its Implications
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Another important concept which we need to know is about the load growth curve for scraper loading. 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 illustrates that beyond a certain point of loading—approximately 85% capacity—loading rates decrease due to material inside the bowl resisting the incoming load. This phenomenon is called the 'law of diminishing returns.' As a result, overloading a scraper can actually reduce productivity. Instead of attempting to fill the bowl to maximum capacity, optimizing the loading amount based on these findings can enhance efficiency.
Examples & Analogies
Imagine trying to stuff a suitcase so full that you can hardly zip it up. The more you add, the harder it gets to get more items inside. Similarly, filling a scraper beyond a certain point actually slows down the loading process instead of speeding it up.
Haul and Return Time Factors
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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 times are crucial components of cycle time, influencing how long it takes the scraper to carry loads to their destination and return to pick up more. These times vary based on factors like travel distance and machine speed, which can be affected by site conditions. Proper maintenance of the haul route can significantly optimize these times, directly impacting productivity and efficiency.
Examples & Analogies
Consider a school bus route. If certain streets are well-maintained and clear, the bus can make its rounds faster. Similarly, the condition of the haul route impacts how quickly scrapers can make their trips, affecting total productivity.
Dumping Time Variables
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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 is affected by several factors including the scraper size and the type of material being dumped. Larger scrapers take longer to dump their loads, particularly if the material is cohesive or if the dump site is congested with other machines. Understanding these variables helps in estimating accurate cycle times, thus aiding in more efficient project planning.
Examples & Analogies
Imagine a construction worker trying to dump a load of sand versus a load of bricks. The cohesive nature of the bricks makes dumping much slower. Hence, the complexity of the material being handled can affect how quickly it can be unloaded.
Turn Times in Different Conditions
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Now we are discussing about the turning time of the scraper. So, you can see that the turn time is basically not affected by the type or the size of the scraper...
Detailed Explanation
Turning time is generally consistent regardless of scraper type or size but may vary based on whether the turning happens in a cut area (which is often more congested) versus a fill area. This awareness can aid in project scheduling, considering that turning during loaded conditions can slow down operations compared to turning when the scraper is empty.
Examples & Analogies
Think about trying to turn a bicycle in a crowded area versus an empty parking lot. In a crowded space, it's slower because you have to navigate through obstacles. Similarly, scrapers take longer to turn in congested cut areas compared to open fill areas.
Summary of Cycle Time Components
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So, far we have discussed about the cycle time of the scraper. So, we have the 2 different parts of the cycle time, one is fixed and the other one is it variable...
Detailed Explanation
The cycle time for scrapers is a combination of fixed time components, such as loading, dumping, and turning, along with variable time, which is mostly related to hauling and returning. Understanding both components helps in developing strategies for improving overall efficiency and productivity in operations involving scrapers.
Examples & Analogies
It's similar to a chef preparing a meal—there's a set amount of time needed for chopping vegetables (fixed) and variable time depending on how long the dish takes to cook based on heat settings and sizes of portions (variable). The chef must account for both aspects to serve meals efficiently.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Cycle Time: A complete range of time actions involved in the scraper's operation.
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Fixed Time: Time impacts that do not depend on travel distance.
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Variable Time: Time impacts that are dependent on travel distance and machine speed.
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Loading Time: How long it takes to fill the scraper.
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Load Growth Curve: A concept highlighting efficiency drop when overloading.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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When the scraper is filled to 85% capacity, production rates decrease due to internal material resistance.
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A well-maintained haul route can reduce return time and improve overall cycle time significantly.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
🎵 Rhymes Time
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Cycle time has seven parts, each plays a role from the start. Loading, hauling, dumping are a must, to keep the scraper's work a trust.
📖 Fascinating Stories
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Imagine a scraper on a journey, every step it takes matters! Each part of its travel—from loading to dumping—contributes to how long it takes to finish its job well.
🧠 Other Memory Gems
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Remember ADBT for Acceleration, Deceleration, and Braking Time!
🎯 Super Acronyms
CYCLE helps to remember
- C: – Components
- Y: – Yield time
- C: – Conditions
- L: – Load impact
- E: – Efficient use.
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Cycle Time
Definition:
The total time taken for one complete working cycle of the scraper, including all phases from loading to returning.
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Term: Load Time (LT)
Definition:
The time required to load materials into the scraper.
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Term: Haul Time (HT)
Definition:
The time spent transporting the load from the source to the dump site.
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Term: Dump Time (DT)
Definition:
The time taken to dump the load of materials at the designated site.
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Term: Return Time (RT)
Definition:
The time spent returning the scraper to the loading area after the dump.
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Term: Spot Time (ST)
Definition:
The time taken to position the scraper properly for loading.
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Term: Turn Time (TT)
Definition:
The duration required for the scraper to turn around during its operation.
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Term: Acceleration, Deceleration, and Braking Time (ADBT)
Definition:
The time required for the scraper to accelerate, decelerate, and apply brakes.
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Term: Load Growth Curve
Definition:
A graphical representation that shows the relationship between loading time and the percentage of payload in the scraper's bowl.