1. Earth Moving Equipment-Scrapers (Part-2)

In this lecture, we are going to discuss or we are going workout some problems on the estimation of the productivity of the scraper. And we will also work out some problems on balancing the number of scrapers and the pushers which are the interdependent machine.

In this part of the lecture, the focus is on understanding how to estimate the productivity of a scraper, which is a type of earth-moving equipment. Productivity estimation refers to calculating how efficiently the scrapers can move earth from one location to another. Additionally, the interdependence of scrapers and pushers—machines that assist scrapers in loading material—is explored, as managing their numbers effectively can optimize productivity on a construction site.

Think of this as planning a team project where one person (the scraper) does the heavy lifting of information, while another (the pusher) helps by providing necessary resources. If there are too many scrapers and not enough pushers, some scrapers will be idle, waiting for their helper, hence reducing overall productivity.

The swell factor has given as 0.80. So, with the help of the swell factor you can do the conversion like from loose volume, you can convert it into bank volume or vice versa and you should know that this swell factor will increase by 10 % due to pushing.

The swell factor is a crucial concept in excavation and earth-moving operations, as it relates to how the volume of soil changes when it is disturbed. In this case, the swell factor of 0.80 indicates that for every unit volume of loose soil, it occupies more space than when it is compacted (or in bank state). When the scraper is assisted by a pusher, the pressure exerted compact the soil further causing the swell factor to increase by 10%, thereby increasing its effective volume when loaded.

Imagine filling a sponge with water. The sponge expands when water is added, representing the expansion of loose material. When a pusher pushes the scraper, think of it as squeezing the sponge, compacting more water into a smaller volume, thus the material becomes heavier and takes up more space when loaded into the scraper.

The empty weight of the scraper is given in kg. The maximum rated load it can carry is 34,019.42 kg. We have to check whether your load or material within your bowl is going to be within this safe operating weight.

Every earth-moving machine has an empty weight and a maximum safe operating weight. The empty weight is the weight of the machine without any load, while the maximum rated load is the heaviest amount of material the machine can safely transport. It is critical to ensure that the combined weight of the empty scraper and the load does not exceed this maximum weight to avoid mechanical failures or accidents.

Think of carrying a backpack. If your backpack can hold a maximum of 10 kg (34,019.42 kg in the scraper's case) and weighs 2 kg (empty weight), you can only add 8 kg of items. If you exceed the weight limit, just like machines, your backpack may break, or you could hurt yourself. Ensuring safety limits are respected is crucial.

Now, you need to calculate the travel time. So, we have calculated the speed. You know the speed for different segments. You know the haul distance for different segments. Now, you can calculate the travel time.

Travel time is calculated by dividing the distance traveled by the speed of the scraper for that segment. By determining travel times for each segment of the haul route, you can add them together to get the total cycle time which includes all activities (like loading, dumping, and travel). This calculation is essential for project planning and determining how many loads can be processed in a given time frame.

Imagine you’re driving home from work. If you know the distance to your home and your average speed, you can calculate how long it will take you to arrive. Similarly, in construction, understanding travel time helps in efficiently managing operations and scheduling.

So as I mentioned earlier, we need to balance the interdependent machines so that one need not wait for the other. So, that way you can reduce the cycle time of the production and you can increase the productivity.

Balancing the number of scrapers and pushers is necessary to optimize productivity. If only one pusher is assigned to multiple scrapers, it should be configured so that there’s minimal downtime for all machines involved. By calculating the cycle times of the machines, you can determine the optimal number of scrapers that should be paired with each pusher to streamline operations without delays.

Consider a restaurant kitchen where chefs (scrapers) are waiting for ingredients (pushers) to be delivered. If there’s only one delivery person (pusher) for five chefs, the chefs will have to wait, reducing the kitchen’s efficiency. Having enough delivery staff ensures all chefs can work continuously without downtime, thus increasing the restaurant's output.

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