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A short class with Sarah and her students. The other ways are under More.
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Today, we are going to explore the concept of cycle time in scrapers and its components. Can anyone tell me what cycle time includes?
Does it include loading and dumping times?
Exactly! The formula for cycle time combines Load Time (LT), Haul Time (HT), Dump Time (DT), Return Time (RT), Spotting Time (ST), Turn Time (TT), and ADBT. ADBT stands for Acceleration, Deceleration, and Braking Time.
What makes fixed time different from variable time?
Good question! Fixed time is independent of travel distance while variable time, which includes haul and return times, is heavily dependent on the distance traveled and speed of the machine.
And how does the machine speed get affected?
Machine speed can be influenced by several factors including underfoot conditions and equipment types. It is crucial to optimize this for efficiency!
In summary, understanding fixed and variable times can help in planning operations better to enhance productivity.
Let’s discuss loading time! Loading time remains fairly consistent for different scraper sizes. Can anyone guess why?
Is it because they are usually assisted with pusher loaders?
Exactly! Now, have you heard of the load growth curve? It’s an important principle in loading scrapers.
What does it show?
It shows that loading beyond a certain point—typically more than 85% of the scraper bowl—can decrease production due to increased resistance.
So we should avoid overfilling to stay efficient?
Exactly! Always aim for optimum loading time by referring to the load growth curve. This aids in maintaining operational efficiency.
Remember, optimizing loading time is critical for improving overall scraper productivity.
Now let’s talk about haul and return times. Does anyone remember the factors affecting these times?
It’s mostly about distance and speed, right?
Correct! Additionally, maintaining the haul route can significantly reduce these times. Why do you think that is important?
It probably helps avoid wear and tear on the machine and increases speed!
Exactly! An effectively maintained haul route minimizes resistance and improves overall productivity. What factors might influence route maintenance?
Weather conditions could make it tougher to maintain!
Right! The effort invested in maintaining these routes pays off in terms of reduced cycle time and cost.
Remember, keeping a clean and clear haul route is key to effective scraper operation.
Let’s shift our focus to dump time. So, what can you tell me influences dump time?
I think it varies based on the size of the scraper and type of material?
Great point! Additionally, site constraints and congestion at dump sites can further impact dump times.
What’s the safest way to dump?
The safest practice is to dump before turning, especially when loaded. This reduces risk during operations.
So, what is the average turning time affected by?
The average turning time is typically higher in cut areas because of congestion and equipment involvement. Always prioritize safety!
In summary, understanding the implications of dump time enhances both productivity and operational safety.
Components that do not depend on travel distance, including load, dump, and turn times.
Components that depend on distance and speed, including haul and return times.
The phenomenon where loading rate decreases after a certain threshold, affecting production.
Loading time is a steady climb, overloading gives us less time.
Imagine a baker who has a tray. If too much dough fills it, some won't blend in—they only cause trouble and make the baking murky.
To remember the cycle time components, think 'L-D-H-R-S-T-T-A' for Load, Dump, Haul, Return, Spot, Turn, and then Acceleration.
CYCLE for remembering: C for Components, Y for Yield, C for Capacity, L for Load time, E for Efficiency.
Term
What is ADBT?
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Term
Define Load Growth Curve.
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The total time taken for a scraper to complete one full operation cycle, including various time components.
The time taken to load materials into the scraper.
The time taken to dump materials from the scraper.
The time taken to transport materials from the loading site to the dumping site.
The portion of cycle time that is independent of travel distance.
The portion of cycle time that depends on travel distance.
A graphical representation showing the relationship between loading time and the percentage of payload.
The section outlines the various components and calculations involved in determining the cycle time of a scraper, highlighting the significance of load time, dump time, variable and fixed times.
The section elaborates on cycle time calculations for scrapers, detailing fixed and variable time components such as loading, hauling, dumping, and turning times. It also emphasizes the importance of proper maintenance of haul routes, the effects of loading methods, and optimizing production by understanding the dynamics of dump time and load growth curve.
In the context of scrapers, the cycle time is a critical measure that incorporates various durations, represented mathematically as:
Cycle time = LT + HT + DT + RT + ST + TT + ADBT
Where:
The cycle time can be divided into fixed and variable components.
Loading time is notably consistent across different scraper sizes and is often supported by pusher loaders. Key points to note include:
Hauling and return times vary based on site conditions, maintenance of haul routes, and machinery speed. Proper maintenance reduces cycle time and improves productivity.
Understanding these components enables effective planning and optimization of construction operations, ensuring timely project execution and cost efficiency.