6.1 - Balancing Number of Scrapers
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Introducing Scrapers and Pushers
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we'll explore the critical roles that scrapers and pushers play in earthmoving processes. Can anyone tell me what a scraper does?
A scraper moves earth from one place to another, right?
Exactly! And pushers help load material onto scrapers. They work together to optimize performance. Now, why do you think it’s important to balance their operations?
So that they don't waste time waiting for each other?
Correct! Less waiting time means better productivity. Remember, efficient collaboration between machines enhances overall workflow.
Cycle Time Understanding
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let’s dive deeper into cycle times. What do you think a cycle time refers to?
Is it the time taken for one complete loading and unloading operation?
Yes, exactly! For both scrapers and pushers, understanding their cycle times is vital. Can someone recall the average cycle time for a scraper from our previous class?
I think it was 7.78 minutes?
Well done! Now, if a pusher takes 1.37 minutes, why is it crucial to analyze these times?
To see how many scrapers one pusher can effectively service!
Exactly! Lower cycle time for pushers means they can serve more scrapers, but we need to calculate it carefully to benefit from this.
Estimating Productivity
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s discuss how we estimate productivity. Who can remind us what factors affect the estimation of a scraper's productivity?
The type of soil, its unit weight, and the swell factor!
Exactly! The swell factor particularly increases with the load from the pusher. Can someone explain why?
Because it compacts the material more, leading to denser soil in the scraper?
Correct! These factors together help us refine our productivity estimates, which is essential before balancing the machines.
Balancing the Number of Scrapers
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
So, how do we calculate the number of scrapers needed for one pusher?
We take the ratio of the scraper's cycle time to the pusher's cycle time.
Exactly! Can someone calculate that ratio with our previously discussed times?
7.78 divided by 1.37 is about 5.68!
Right! We can round that number. If we choose 6 scrapers, what considerations should we keep in mind?
We need to check if the productivity will justify the increased costs!
Well said! Balancing operational costs with productivity demands careful analysis.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The focus of this section is on estimating the productivity of scrapers and the importance of balancing scrapers and pushers. It highlights the significance of understanding the cycle times of both machines to enhance efficiency on haul routes, minimize waiting times, and improve overall productivity during construction projects.
Detailed
Balancing Number of Scrapers
In this section, we delve into the critical relationship between scrapers and pushers within the context of construction equipment management. Scrapers, which are primarily used for moving earth, must often work in conjunction with pushers that assist in loading them efficiently.
Key Concepts:
- Interdependence: Understanding the cycle times of scrapers and pushers is crucial for optimizing performance and maintaining workflow on job sites.
- Productivity Estimation: We discuss various factors affecting productivity estimation, including unit weights, swell factors, loading times, and the impact of pushing on material density.
- Cycle Time Calculations: Detailed examples are provided to illustrate how to calculate the cycle times for both scrapers and pushers, emphasizing how a discrepancy in their operational speeds can lead to inefficiencies.
- Balancing Numbers: Finally, the section addresses how to calculate the balanced number of scrapers that one pusher can effectively serve, ensuring a synchronized operation that minimizes waiting time and maximizes throughput.
This comprehensive approach not only aids in estimating the hourly production rates but also guides decisions regarding the optimal number of scrapers to deploy for a given project.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Understanding Cycle Times
Chapter 1 of 3
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The pusher cycle time is going to be relatively smaller than the scraper cycle time. This is because your pusher will be helping the scraper only during the loading phase.
Detailed Explanation
In earthmoving operations, two main machines—the scraper and the pusher—work in tandem. The pusher assists the scraper primarily during loading. Once the scraper is loaded, it can continue its work independently. This results in the cycle time of the pusher being shorter than that of the scraper, as the pusher is not needed after the scraper fills its bowl.
Examples & Analogies
Think of a team of workers loading a truck. One person is loading bags (the scraper), while the other (the pusher) is helping them load. Once the truck is fully loaded, the helper can take a break while the truck drives away. The helper doesn’t need to be there the entire time, making their effort shorter.
Balancing the Number of Scrapers
Chapter 2 of 3
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
The balanced number of scrapers which are served by one pusher is equal to the cycle time of the scraper divided by the cycle time of the pusher.
Detailed Explanation
To ensure efficient operations and minimize wait times for machines, we need to determine how many scrapers one pusher can service. This is calculated by dividing the cycle time of the scraper by the cycle time of the pusher. For example, if the scraper takes 7.78 minutes per cycle and the pusher takes 1.37 minutes, then one pusher can serve approximately 5.68 scrapers. Since we can't use a fraction of a machine, this number can be rounded down to 5 or up to 6.
Examples & Analogies
Imagine a waiter in a busy restaurant. If one waiter can serve a table in 10 minutes and another shorter table takes only 2 minutes to serve, then a single waiter could theoretically manage five tables while one table is being served. However, the waiter could only serve whole tables, not portions, so they might choose to serve either five or six tables at a time.
Evaluating Economic Trade-offs
Chapter 3 of 3
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Now we have to work out the economics of both the cases. If I go for 5 scrapers what will be the associated productivity and production cost? If I go for 6 scrapers what will be the production and unit production cost?
Detailed Explanation
Once the balanced number of scrapers is calculated, it's crucial to evaluate the economic implications of using either five or six scrapers. This involves analyzing the productivity of the scrapers and any associated costs. Higher productivity can reduce the cost per unit of earth moved. However, having too many scrapers compared to the number of pushers can lead to idle machines, increasing costs without increasing output.
Examples & Analogies
Imagine you're running a bakery. If you have five ovens (scrapers) and one mixer (pusher), you can produce a lot of cookies efficiently. But if you buy a sixth oven, you need to check if you can whip up enough dough with the mixer before the cookies bake. If not, that sixth oven would be wasted capacity and money, just sitting empty while you’re working at full capacity.
Key Concepts
-
Interdependence: Understanding the cycle times of scrapers and pushers is crucial for optimizing performance and maintaining workflow on job sites.
-
Productivity Estimation: We discuss various factors affecting productivity estimation, including unit weights, swell factors, loading times, and the impact of pushing on material density.
-
Cycle Time Calculations: Detailed examples are provided to illustrate how to calculate the cycle times for both scrapers and pushers, emphasizing how a discrepancy in their operational speeds can lead to inefficiencies.
-
Balancing Numbers: Finally, the section addresses how to calculate the balanced number of scrapers that one pusher can effectively serve, ensuring a synchronized operation that minimizes waiting time and maximizes throughput.
-
This comprehensive approach not only aids in estimating the hourly production rates but also guides decisions regarding the optimal number of scrapers to deploy for a given project.
Examples & Applications
If one pusher has a cycle time of 1.37 minutes and one scraper has a cycle time of 7.78 minutes, balancing their number leads to deploying about 5 or 6 scrapers per pusher.
When loose material is loaded into a scraper, the swell factor should be increased by 10% for push-loaded scrapers, affecting estimation of productivity.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Scraper has the load so tall, pusher's there to push it all.
Stories
Once upon a time in a construction site, there lived a busy scraper who always needed a friend to help load. His friend, the pusher, made his job easy by pushing the loads carefully, teaching everyone how much better they worked together than alone.
Memory Tools
SPLASH: Scraper Productivity and Loading Sync Harmony.
Acronyms
BSP
Balance Scrapers and Pushers to minimize waiting time.
Flash Cards
Glossary
- Scraper
A machine used in construction to move bulk material like earth or debris.
- Pusher
A vehicle that assists scrapers by pushing material into their bowls for loading.
- Cycle Time
The total time taken for a machine to complete one loading and unloading operation.
- Swell Factor
A ratio representing the increase in volume of material when it changes from a bank state to a loose state.
- Haul Route
The path or distance along which the hopper or scraper moves material to be disposed of.
Reference links
Supplementary resources to enhance your learning experience.