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A short class with Sarah and her students. The other ways are under More.
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Hello class! Today we will discuss the concept of cycle time in scrapers. Cycle time is the total time it takes for one complete operation cycle of a scraper, and it includes several components. Can anyone help me list out these components?
Isn't it Load Time and Haul Time?
Exactly! We also have Dump Time, Return Time, and Spot Time. Together these components make up the cycle time equation: LT + HT + DT + RT + ST + TT + ADBT. Can anyone tell me what ADBT stands for?
I think it stands for Acceleration, Deceleration, and Braking Time!
Correct! ADBT refers to the time needed for acceleration and deceleration. Remember, this helps to calculate both fixed and variable times in the cycle. Now, can anyone explain the difference between fixed time and variable time?
Fixed time doesn't depend on travel distance, while variable time does!
That's right! Fixed time includes loading, dumping, and turning times. Variable time is mainly about haul and return, which depends on the distance to be traveled. Great job, everyone!
Next, let’s talk about loading times. What's the common assumption regarding loading a scraper?
People often think we should fill it to maximum capacity to increase productivity.
That’s correct! But studies show that trying to maximize the load can actually reduce productivity. This phenomenon is shown in the load growth curve. Can anyone explain how this curve works?
As the bowl gets filled, the incoming material has to push against what’s already in the bowl, which can slow down loading.
Exactly! This is known as the law of diminishing returns. Loading beyond a point reduces the efficiency of the scraper. So, what’s a better strategy?
We should find the optimum loading time and capacity instead of filling it to the brim!
Exactly! Always aim for that sweet spot to optimize productivity.
Now, let’s move on to haul and return times. Why are these times variable?
They vary depending on travel distance and speed.
Exactly! And the speed depends on the project conditions. What can we do to enhance the speed on haul routes?
We need to maintain the haul route well to control dust and improve visibility.
Absolutely! Maintaining haul routes ensures that we reduce cycle time and increase productivity. Can anyone mention how we can maintain haul routes?
Using graders or water trucks for dust control!
Well said! The effort spent on maintaining the routes pays off in efficiency.
Let’s now talk about dump times. What affects how long it takes to dump the load?
The size of the scraper and the type of material, right?
Exactly! Cohesive materials will take longer to dump compared to loose ones. Also, what about spatial constraints at the dump area?
If the area is congested with equipment, it might take longer to dump.
Excellent point! Dumping time can be heavily influenced by site conditions. Can anyone recall why scrapers are designed for loose materials?
It’s because they perform better with less resistance, which helps increase productivity.
Correct! Great insights, everyone!
Finally, let’s discuss the role of pushers in loading scrapers. Why is it essential to balance the number of pushers with scrapers?
To maximize efficiency and reduce waiting time, right?
Absolutely! If one machine has to wait on another, it can lead to inefficiencies. Can someone explain how we determine the optimal number of pushers?
By knowing the loading capacity we need and matching it with the number of scrapers!
Right! That ensures smooth operations. I hope you all now understand how various components and machines interact in the process!
Total duration for a scraper's full cycle.
Time components independent of haul distance.
Time components affected by haul distance.
Indicates reduced efficiency beyond optimal loading.
Essential for optimal speed and reduced labor costs.
Scraper time, load it right, not too full to lose the fight.
When a new operator fills the scraper bowl to the brim, a veteran warns, 'Stop! Less is more, for the bulk makes us slow.'
PUSH (P = Pusher that helps, U = Understand the load, S = Speed on route matters, H = Help reduce cycle time).
CYCLE: Comprehensive Yield of Cycle Load Efficiency.
Term
What does the cycle time formula include?
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Term
What is a load growth curve?
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Term
What are the two types of time in cycle time?
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Why maintain haul routes?
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The total time required for a scraper to complete one full operation cycle.
A graph depicting the relationship between loading time and the percentage of payload, highlighting maximum efficiency.
The designated path for traveling between the loading and dumping sites.
Components of cycle time not dependent on travel distance, such as loading and dumping.
Components of cycle time that vary based on travel distance and speed, primarily including haul and return time.
This section details the concept of cycle time in scrapers, including fixed and variable components, optimal loading strategies, and the importance of haul and return times.
The section explores the cycle time calculation for scrapers, breaking it down into fixed and variable components. It discusses loading times, the effects of material conditions, and introduces the concept of a load growth curve, emphasizing the need for optimized loading practices to enhance efficiency and productivity.
This section focuses on the cycle time calculation for scrapers used in heavy machinery operations. The cycle time is defined by the formula:
Cycle time = LT + HT + DT + RT + ST + TT + ADBT
Where:
The cycle time is divided into two parts: fixed time and variable time. Fixed time includes components such as loading, dumping, turning, and the times needed for acceleration, deceleration, and braking. On the other hand, variable time mainly concerns haul and return times, which depend on travel distance and speeds determined by site conditions.
Loading time is generally consistent across scraper sizes, particularly when assistive pushers are used. However, an essential concept is the load growth curve, illustrating that overloading a scraper can lead to reduced production rates due to increased resistance from previously loaded materials. As loading approaches maximum capacity, production begins to diminish, affirming that loading scrapers to full capacity is inefficient.
In regards to haul and return times, it is crucial to maintain haul routes to optimize cycle times and overall productivity. The section also covers dump times and the implications of material types being dumped, plus challenges at dump areas. Ultimately, enhancing the hauling performance directly influences operational costs and efficiency.