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A short class with Sarah and her students. The other ways are under More.
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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.
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!
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.
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.
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.
The time for scraping operations, divided into fixed and variable times.
Time elements such as loading which do not depend on distance.
Number of elements determined by distance, like haul and return.
Pusher-assisted loading which optimizes time.
To keep scrapers rolling fine, load and haul in your time!
Imagine a pusher helping a scraper, once loaded, the pusher backtracks like a helper who finishes a task and moves to support another!
Remember 'LHD RSTTA' for understanding cycle time components.
Use 'HARD' to remember Haul, Acceleration, Return, Dump for cycle time aspects.
Term
What components make up cycle time?
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Term
Define variable time.
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Term
What is back-track loading?
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The total time required for a scraper to perform its operation, including load, haul, dump, return, spot, turn, and braking.
Part of the cycle time that does not depend on the distance travelled.
Part of the cycle time that is dependent on the haul and return distances.
A principle indicating that loading beyond a certain point decreases efficiency due to increased resistance.
A loading method where a pusher assists a scraper during the loading phase and then backtracks to help another scraper.
This section discusses the components of cycle time in scrapers, including fixed and variable times, and elaborates on the loading method known as back-track loading.
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.
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:
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.