How to Properly Engineer Efficiency At Your Aggregates Site.
By Jason Crain
In the years I have been working with conveyors and helping troubleshoot issues, spec systems and supply solutions, I run across the same comment at almost every facility: “We are trying to maximize output and efficiencies with what we have.” Today, market demand is higher than ever, so facilities are forced to increase production or risk losing business to their competition.
The following are a few examples of what I have seen and the steps taken in the field to increase production.
The Downside of Turning It Up
In many cases, operation workers are told to “just turn it up.” In a popular mining television show, they always seem to go down this path: “Just turn it up – I don’t care, just do it.”
So, they turn up the speeds and feed rates, and they run more material. I probably haven’t watched a single episode where they turned up the system and everything went right. Typically, some sort of breakdown or overloading stops all operations, and all operation employees must halt and work together to fix the issue they just created.
Sometimes, they process more product by “turning it up” than they would have otherwise. This is a success, right? Yes and no. They may have reached the quota desired, but at what cost?
What were the labor and lost production costs from the early failure for parts damaged? In some scenarios, the product value outweighs the costs of these failures and downtimes. But not all products are worth their weight in gold.
Have you ever been on a long drive with kids in the car? Similar to production, you have a choice to make. Drive too slowly, and inevitably the question of “Are we there yet?” will come out. And the longer the drive, the more frequent and dire the question becomes. After a while, you may be tempted to drive a bit faster. But what are the potential consequences? If you go too fast, you may get a ticket or, worse, cause a wreck.
Those are the obvious consequences, but what about the other components of that drive? Fuel efficiency, tire wear, shock impact or a damaged windshield. Now you start calculating the true cost of driving faster. That may mean less fuel efficiency at higher speeds or more wear on tires from turning too quickly.
The shocks will take higher levels of impact from hitting bumps or potholes. And a rock is more likely to crack your windshield at higher speeds. Understanding all consequences of driving faster – not just the potential results of getting a ticket – can help inform a decision based on true cost.
Is Bigger Always Better?
One way to produce more and increase efficiencies is to get newer, bigger equipment. But that is expensive and, in many cases, not an option for existing facilities.
So, what is the solution? Good operations managers will start by reviewing a system and identifying bottlenecks – areas in the operation that slow down the entire process. Next, they will look for equipment or process changes to increase capacity in those areas.
Some may say, “Let’s get a bigger, faster machine here, something that will double capacity.” Problem solved, right? Not necessarily. How does this increase in production affect all the components downstream? Can these components keep up with the new load?
I was working with a recycling facility that had invested a lot of money in new equipment to solve an overflow issue on one of their conveyors and increase capacity. They had a machine that could process material at a specific rate but ran only at 60% capacity.
So, like our first example, they said to “turn it up.” When evaluating true cost, they found that the next conveyor was already running at maximum speed and was only designed for 60% of the previous machine’s capacity. If the process were “turned up,” material would build up so much that it eventually could fall off the conveyor’s sides. The material landing where it shouldn’t, could damage the system components and add labor hours needed to clean up the overflow material. It only appeared that going bigger would fix the issue.
The recycler decided to get a larger conveyor to handle the increased capacity. It fixed this conveyor’s issue but transferred the overload issue down the line. However, the goal was in sight, and since so much had been invested, there was no turning back. It wasn’t until the operations manager got to a sorting line with the human element that he was forced to stop, review and reassess.
To handle the larger infeed of material, the same solution of making the belt bigger and wider had been implemented. But the issue was that his employees weren’t all 7 ft. tall and could no longer reach the belt’s center to sort the material.
As a result, some product made it too far in the process, eventually damaging conveyors and equipment downstream. Additionally, ergonomic issues were created, giving workers sore backs from reaching so far over the conveyors. At this point, I was called in to review the facility and work with them to pinpoint the best solution.
After analyzing the material flow, the facility team and I identified specific system lines that were not being overloaded. This allowed us to put in a secondary screen, reducing the total amount of product flowing through the primary line. Our flow analysis of the entire system allowed us to identify these existing conveyors that could handle the needed flow for this facility.
The Value of System-Wide Analysis
The final example I frequently see in aggregate operations is a feed conveyor that transfers material from a crusher or hopper. The plant manager wanted to increase the feeder’s production rates and speed. He did his due diligence and reviewed bottlenecks, conveyor speeds and capacity.
With this information, he decided that turning up the feed would not affect the downstream processes. He then noticed that the conveyor belt would now last only half the time. The math makes sense: increase the speed and tonnage, then the belts won’t last as long. So, the manager’s solution was to purchase a thicker, stronger, more expensive belt. But then he realized that the belt was still lasting only as long as the original belt.
We were asked to review their system. Their full system analysis was fantastic in terms of capacity. However, they missed analyzing the feeder components and seeing if they adequately supported the new thicker, stronger belt.
The system was specifically designed for the old belt. After reviewing the original belt’s failures, we saw they achieved the maximum life wear of the top cover and very little carcass damage – perfect wear for a belt. But when reviewing the damage and failure on the new belt, we found rough edges and a torn-off section. However, belt cover wear was minimal.
Specific conveyor components will generally accommodate several different belt specifications. For example, the pulleys used on this system were large enough to meet minimum pulley requirements for both the old and new belts.
But the system component that did not fit the new belt was the idlers. The new belt was thicker and too rigid to settle in the idlers; this caused all sorts of tracking issues when the belt was unloaded. While the belt was loaded and maintenance would watch it run, it tracked perfectly. But at the end of every shift, or if the hopper ran dry of material, they could not get the belt to settle in the troughing rollers, causing it to mis-track and rub the sides of the conveyor.
The result was more damage every day. After running the system analysis and identifying the issue, we adjusted the idler style to allow the belt to sit correctly and handle the new load and speeds. This change doubled the belt life and nearly doubled their daily capacity.
So, what is the best way to increase capacity? The answer is different for each facility and each system. Even as a professional in this field, I can’t always say that one solution is better than another. But in each scenario, I work with various specialists and tools to analyze an entire system. These tools can calculate the half-life of a component based on speed, loads, belt construction, etc.
I encourage you to reach out to your supplier or local belt specialist. See if they have the capabilities to run full engineering on all your systems and give you a report to find the best direction for your application. Every action has a reaction – wouldn’t it be nice to know what that reaction would be before you invest in changes that may or may not work?
Jason Crain is business development manager – heavy-duty fabricated with Mi Conveyance Solutions and has been in the conveyor belt/systems industry for 25 years. He started in the field with installs and teardowns, then transitioned to custom-fabricated operations and sourcing. Crain helps customers find a solution to their needs or problems. For more information, visit MiConveyanceSolutions.com.