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A short class with Sarah and her students. The other ways are under More.
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Today, we'll break down the cycle time of a scraper. Can anyone tell me what cycle time consists of?
Isn't it just the time it takes to complete one full loading and dumping process?
That's a part of it! The cycle time actually consists of Load Time, Haul Time, Dump Time, Return Time, Spot Time, Turn Time, and Acceleration/Deceleration/Braking Time. These can be broadly split into fixed and variable times. Who remembers what fixed time includes?
I think it includes things like loading and dumping times, right?
And turning too! Fixed times don't depend on distance.
Exactly! And the variable time includes haul and return time, which depend on distance and speed. Great job!
When it comes to loading time, why do we see a consistent load time regardless of scraper size?
Because of the pusher assisting the scraper?
That's right! But what happens if we try to maximize the payload too much?
It results in diminishing returns as the material fills the bowl to capacity and slows down the loading rate.
Exactly! We use a load growth curve to determine the optimal loading time. Can anyone explain that concept?
The curve shows that beyond a certain point, the rate of loading decreases.
Great summary! It's essential to load efficiently to maximize production.
Next, let's talk about the haul route. How does maintaining the haul route impact cycle time?
If we maintain it well, it reduces rolling resistance and increases travel speed, right?
Exactly! And this ultimately improves the productivity of the machine. What other benefits does maintaining the haul route provide?
It reduces maintenance costs and extends the life of the machines.
Spot on! Investing in haul route maintenance pays off in the long run.
Let's move on to dump time. What factors can influence the dump time of a scraper?
The size of the scraper and the type of material it handles?
Correct! And how does congestion at the dump area affect this?
If it's congested, it might take longer to position itself for dumping.
Right! And understanding turn time varies between cut and fill areas. Who wants to explain that?
The turn time in the cut area is typically longer due to more congestion from other machines.
Great observation! Understanding these concepts improves our overall operational efficiency.
The complete time for the loading and dumping process.
Parts of cycle time that are unaffected by travel distance.
Parts of cycle time that change based on distance and speed.
A graphical analysis showing optimal loading and production relationships.
The designated path for transport, crucial for efficiency.
In the scraper’s cycle, time does flow, haul and return, keep the speed in tow.
Imagine a scraper named Sam who lifts, hauls, and dumps without any rifts. He knows to maintain the haul route, to keep on moving without a doubt.
Remember the acronym 'LHDSPT' for Load, Haul, Dump, Spot, Turn - key times in the production cycle.
Use 'FVV' to recall Fixed Time, Variable Time, and their roles in cycle time components.
Term
What is the meaning of Load Growth Curve?
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Term
What does Variable Time involve?
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The total time to complete one loading and dumping cycle in a scraper.
Components of cycle time that do not depend on distance traveled.
Components of cycle time that vary depending on distance and machine speed.
Graphical representation illustrating the relationship between loading time and payload percentage.
The path taken by scrapers while hauling loads, which impacts efficiency.
The time taken for the scraper to unload its material.
Time it takes for the scraper to change direction, varying by site conditions.
This section explores the components of cycle time in scrapers, focusing on haul and return times, and highlights the significance of maintaining optimal loading practices.
The chapter delves into the elements contributing to cycle time in scrapers, particularly examining haul and return times, and discusses load growth curves, optimum loading practices, and the importance of maintaining haul routes to enhance operational efficiency.
The cycle time for a scraper is defined as the sum of several components: Load Time (LT), Haul Time (HT), Dump Time (DT), Return Time (RT), Spot Time (ST), Turn Time (TT), and Acceleration/Deceleration/Braking Time (ADBT).
Components of Cycle Time: Each component plays a unique role in the overall cycle time:
Loading Time: The loading time is consistent regardless of scraper size due to pusher assistance. Research indicates that trying to maximize payload can lead to diminishing returns, as resistance increases with material fill, reducing the loading rate.A load growth curve illustrates that the production rate peaks before reaching maximum capacity.
Haul and Return Time: This variable time is dependent on site conditions such as rolling resistance and grade resistance. Proper maintenance of the haul route is imperative to optimizing speed and overall productivity, ultimately reducing unit costs.
Dump Time: The dump time depends on scraper size and material type. Dumping methods vary based on project site constraints.
Turn Time: Insights reveal that the turn time varies based on where the turn occurs (cut area vs fill area) due to congestion levels.
In summary, understanding and optimizing these components is critical to improving the efficiency of scraper operations.