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Learn it your way
A short class with Sarah and her students. The other ways are under More.
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Let's start with loading time. Can anyone tell me how we calculate loading time for a truck?
Is it just the bucket loads multiplied by the cycle time?
Exactly! The loading time is calculated as the number of bucket loads multiplied by the bucket cycle time. This means that the higher the volume we need to load, the more time it will take.
What if the material isn't very dense?
Great question! If the material is less dense, you might have more volume while staying within the truck's gravimetric capacity. Just remember, always check that the load weight is within safe limits.
Got it! So, we really need to be careful about what we load!
Yes! Balancing capacity is crucial to prevent overloading, which can cause wear and tear on the trucks.
Next, let's discuss material density. Why do you think it's important to consider the density of the material?
Because it affects how much weight we can load in the truck without going over its capacity?
Correct! If the material is dense, like wet sand or rocks, it increases the load significantly and could lead to overloading. Can anyone tell me the outcome of overloading?
It can wear down the tires faster and even cause other parts of the truck to fail!
Exactly! And since tire costs can make up about 35% of operating costs, it's essential to monitor our loads carefully.
I see how that could build up costs quickly!
Now let's look at haul and return times. How are these calculated?
I think we calculate haul time based on distance and speed?
That's right! You need to know the speed from the performance chart, which depends on the weight of the truck and resistances on the site. What about return time?
Isn't it the same, but the truck is empty?
Exactly! The return speed is usually higher because it's unladen, which makes return time shorter.
So we should always account for both times when planning?
Exactly! It’s crucial for accurate productivity estimations.
Let's explore balancing interdependent machines, specifically trucks and excavators. Why is this important?
It helps to avoid waiting times and ensures maximum productivity?
Correct! Balancing means ensuring the number of trucks matches the excavator's capabilities. A rule of thumb is 4 to 5 times the bucket size of the truck. How do we find the right number of trucks?
By dividing the truck cycle time by the excavator's cycle time?
Yes! This gives us a balanced number of trucks that will align production efficiently without causing idle time.
What happens if we have too many or too few trucks?
Great question! Too few trucks mean idle time for the excavator, while too many can lead to wait times for trucks.
Let's solve a problem together. If a loader has a bucket capacity of 2.2 meters cubed and truck capacity of 10.3 meters cubed with a fill factor of 90%, how many bucket loads do we need?
Would it be 10.3 divided by 2.2 times 0.9?
Correct! After you calculate, what is your rounded result?
It's 5.2, so I round it down to 5 loads.
Perfect! And what's the resulting truck payload?
It would be 9.9 meters cubed!
Excellent work! This practical example reinforces how we apply our formulas and concepts in the real world.
Example of calculating loading time: If a truck undertakes 5 loads, each taking 1.1 minutes, loading time is 5 x 1.1 = 5.5 minutes.
Example of balancing: If the excavator operates at a cycle time of 1.1 minutes, and each truck cycle time is 39.5 minutes, the number of trucks needed is 39.5/1.1.
To load the truck, do it right, count the buckets tight!
Imagine a truck where every heavy load made it sigh, it whispered, 'Check my load to keep me spry!'
LOAD - Loading time, Overloading consequences, Adjust weighing, Dump without issue.
B.E.T - Balance Excavation and Truck for Efficiency.
Term
What is gravimetric capacity?
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Term
How do you find the truck production volume?
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The maximum safe weight load that a machine is rated to handle as defined by the manufacturer.
The total time taken to load material onto a truck, calculated by the number of bucket loads multiplied by cycle time.
The time taken to unload material from a truck, influenced by machine type and material characteristics.
The time required for a truck to travel from the loading area to the dumping area.
The time required for an empty truck to return to the loading area.
The process of aligning the number of trucks with excavators to achieve optimal production efficiency.
This section focuses on estimating truck production by understanding loading and unloading times, machine capacities, and balancing interdependent machines.
The section elaborates on crucial factors such as loading time based on gravimetric capacity, the impact of material density, and methods for calculating haul and return times. It also emphasizes the importance of balancing the number of trucks with excavators for optimal production efficiency.
In this section, we discuss the critical aspects of estimating truck production, which involves understanding loading time, gravimetric capacity, and the impact of material density. Loading time is calculated as the number of bucket loads multiplied by the bucket cycle time, while gravimetric capacity, defined by manufacturers, determines the maximum safe load for machines. Additionally, material density influences the weight that can be safely loaded.
We also examine the dumping time, which varies with the type of machine and material flow characteristics, as well as haul and return times based on truck speed and project site resistances. Balancing the capacity of trucks and excavators is essential, where the optimal number of trucks typically ranges from four to five times the bucket capacity. The interaction and cycle times between trucks and excavators are critical to maintain productivity without idle time. Lastly, we will explore a practical example that encourages understanding through problem-solving.