3 - Haul Time and Return Time
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Understanding Haul Time
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Today, we are going to learn about haul time. Can anyone tell me what factors we need to consider when calculating haul time?
Is it the distance we need to travel and the speed of the truck?
Exactly! The haul time depends on the haul distance and the speed of the truck. Remember, speed can be derived from performance charts. Can anyone recall what factors can affect speed?
The weight of the machine and any resistances at the site, like rolling resistance?
Right again! The weight and resistances are essential. Good job! Let's summarize: haul time = distance/speed. Keep that equation in mind.
Gravimetric Capacity
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Now let's discuss gravimetric capacity. Can anyone explain what it is?
It's the maximum weight that a machine can safely handle.
Correct! It's critical to adhere to this capacity to avoid damage. If we overload, what might happen?
The machine could break down, or tires could wear out faster!
Spot on! Companies could incur more costs from wear and tear. Always check weight against the machine's rated capacity before loading.
Dumping Time and Conditions
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Let's talk about dumping time next. Why might this vary on a construction site?
It depends on the type of dump truck, like rear or bottom dump.
Absolutely! Dumping time can differ based on truck type, but what else impacts it?
The materials being dumped? Like if they are sticky or loose?
Exactly, and congestion in the dumping area can delay the process too. Many machines working at once means longer waits.
Balancing Trucks and Excavators
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Now, let's explore how to balance the number of trucks needed for an excavator's capacity. Why is this balance important?
To ensure maximum loading efficiency and reduce idle time?
Exactly! The ideal ratio should be around 4 to 5 times the bucket size. Why might we round the balance number of trucks down?
To prevent the loader from overworking and to avoid breakdowns!
Well said! Always consider the economic implications of balancing these resources.
Introduction & Overview
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Quick Overview
Standard
The section delves into the calculations of haul time and return time, emphasizing the influence of loading parameters and site conditions on the efficiency of machinery. It also warns against overloading machines, defines gravimetric capacity, and includes methods to balance the operations of trucks and excavators for maximizing productivity.
Detailed
Summary of Haul Time and Return Time
Understanding haul time and return time is crucial for optimizing performance in construction machinery operations. Haul time is calculated using the distance to traverse and the speed of the machinery, which can be determined from performance charts by considering the machine's weight and on-site resistance. The return time can be calculated similarly, noting that an unloaded truck usually moves faster than a loaded one. The gravimetric capacity of a machine, which refers to the safe load it can handle as defined by the manufacturer, must be adhered to avoid mechanical failure and excessive wear. Overloading not only risks equipment integrity but also leads to increased operating costs such as higher tire replacement expenses.
Factors affecting dumping time include the type of dump truck—be it rear dump, bottom dump, or side dump—and site conditions. Loading methods such as utilizing sideboards to increase truck volume must be evaluated against the potential risks of exceeding gravimetric limits. Understanding the balance between truck and excavator productivity is essential for improving efficiency, indicating the ideal truck capacity should be four to five times the excavator's bucket capacity. Calculating this balance allows site managers to optimize operations, minimizing idle times and maximizing throughput.
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Loading Time Calculation
Chapter 1 of 7
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Chapter Content
But the loading time will be number of bucket loads multiplied by the bucket cycle time.
Detailed Explanation
Loading time is calculated based on how many bucket loads you're moving and how long each load takes to be loaded. To find loading time, you simply take the total number of cycles (bucket loads) and multiply it by the time it takes to load each bucket. This helps in planning how long it will take to fill a truck or container needed for transport.
Examples & Analogies
Imagine you're filling a bucket with water from a well. If it takes you 2 minutes to fill one bucket and you need to fill 5 buckets, your total loading time will be 10 minutes. This principle applies in construction where machines load materials into trucks.
Understanding Gravimetric Capacity
Chapter 2 of 7
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For every machine what is this safe operating load in terms of weight is given by the manufacturer, so that we call it as a gravimetric capacity.
Detailed Explanation
Gravimetric capacity refers to the maximum weight that a machinery can safely carry. Each piece of equipment, whether it's a truck or loader, has a manufacturer's specified limit. If this limit is exceeded, it can cause damage to the machine, leading to increased maintenance costs and potentially expensive repairs.
Examples & Analogies
Think about carrying a backpack. If you fill it beyond a certain weight, it becomes cumbersome and can break. Just like you, machines also have weight limits to ensure they operate effectively without risking damage.
Checking Load Weight for Safety
Chapter 3 of 7
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Check truck load is less than rated gravimetric payload.
Detailed Explanation
It's crucial to ensure that the load weight in the truck is within the safe gravimetric capacity. This can be checked by multiplying the density of the material by the volume load to get the total weight. Overloading can lead to serious machinery failures and increased repair costs.
Examples & Analogies
Consider a bus carrying passengers. If more passengers get on than the bus can handle, it may break down or have an accident. Similarly, if a truck carries more weight than it’s designed for, it can lead to breakdown or accidents.
Impact of Material Density on Loading
Chapter 4 of 7
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Chapter Content
But if the material is going to be denser like wet sand or other denser material, what happens is there are more chances that your machine maybe overloaded.
Detailed Explanation
The density of the material being loaded affects the total weight and hence the loading practices. Heavier materials can lead to overheating and excessive wear and tear on machinery, making it crucial to monitor. Proper training about material properties can ensure that safe loading practices are followed.
Examples & Analogies
Imagine trying to fit a heavier load of bricks into a truck versus loading in fluffy pillows. The bricks are denser and heavier, meaning you would have to be much more careful about how many you load in.
Dumping Time Factors
Chapter 5 of 7
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So, as we discussed earlier the dumping time will depend upon the type of hauling unit whether it is going to be rear dump or bottom dump or side dump accordingly the dump time will vary.
Detailed Explanation
The time taken to dump the material from the truck depends on the type of dumping mechanism used—like rear, bottom, or side dump. Additionally, the nature of the material (whether it's sticky or heavy) and congestion in the dumping area also influence the total dumping time.
Examples & Analogies
Consider pouring a jug of water. If the jug has a spout, it pours quickly (like a bottom dump). If there’s no spout, it takes longer and is messier (like a rear dump). Congestion at the site can be compared to trying to pour water in a crowded kitchen—you're blocked by other activities.
Return Time Calculation
Chapter 6 of 7
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The return time is the same way using truck manufacturer performance chart, but here the truck will be in the unloaded condition, empty weight, and consider the resistances also.
Detailed Explanation
To calculate return time, we refer to the performance chart when the truck is empty. The distance back to the loading site and any resistances such as gradients will factor into how fast the truck can return for another load. Generally, return time will be shorter due to the truck being unloaded, allowing it to drive faster.
Examples & Analogies
Imagine riding your bike uphill to carry groceries—it's slow and difficult. But coming back down, you're much quicker because there's no load, demonstrating how weights affect speed.
Balancing Trucks and Excavators
Chapter 7 of 7
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So, balancing the capacity of the hauling equipment and the excavator bucket size will result in maximum loading efficiency, and reduce total cost.
Detailed Explanation
Balancing the number of trucks with the excavators is crucial. Ideally, the truck's capacity should be four to five times that of the excavator's bucket capacity to optimize the cycle time and reduce waiting time. If the loads are balanced, both machines will operate at maximum efficiency.
Examples & Analogies
It's like balancing the number of players on a sports team. If you have more players suited for offense but not enough on defense, your team won't perform well. Similarly, the correct balance between trucks and excavators leads to optimal performance on site.
Key Concepts
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Haul Time: The time taken to transport materials from one location to another, calculated based on distance and speed.
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Gravimetric Capacity: The maximum load a machine can handle safely without risk of damage.
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Dumping Time: Varies based on the truck type and material being dumped.
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Balancing Machines: Ensuring optimal productivity by matching truck and excavator capacities.
Examples & Applications
If a truck has a speed of 30 km/h and needs to travel 120 km, the haul time would be 4 hours.
An excavator with a 2 m³ bucket should ideally have a 10 m³ truck for optimal operation.
Memory Aids
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Rhymes
For haul and return, don't be a fool, just check your weight and follow the rule.
Stories
Imagine you're at a construction site with a truck filled to the brim, but suddenly it tips over because it was overloaded. That’s the importance of knowing your truck's capacity!
Memory Tools
Remember 'G.H.A.T.' for Gravimetric, Haul time, Assess risks, and Truck capacity.
Acronyms
Use 'H.C.R.' for Hauling, Capacity, and Return time.
Flash Cards
Glossary
- Haul Time
The time taken for a truck to travel a specified distance for loading or unloading.
- Return Time
The time taken for a truck to return to a loading area after dumping its load.
- Gravimetric Capacity
The maximum weight a machine can safely handle, as specified by its manufacturer.
- Dumping Time
The amount of time required to unload materials from a truck.
- Loading Cycle
The time required to load a truck before it departs for dumping.
- Congestion
The overcrowding of construction machinery at a dump site, which can delay operations.
- Performance Chart
A graphical representation of a machine's operational capabilities under various conditions.
Reference links
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