by Roy OlsenIt’s important to consider several factors when selecting the right equipment for a mill. One of the most important factors for making an informed choice is understanding a machine’s total cost of ownership (TCO). We did a case study on TCO of the VersaMill®, a traditional roller mill, and a hammer mill to show our customers what this looks like. To make our calculations, we considered purchase price, maintenance, and energy use.
What Is a VersaMill®?
RMS spent years designing and testing the VersaMill® advanced roller mill to provide superior performance compared to traditional roller mills. It is a direct-driven roller mill with no belts, allowing for independent roll speed and ratio adjustments.
These features allow the VersaMill® to achieve particle sizes and distributions that neither the standard roller mill nor the industrial hammer mill can achieve.
VersaMill®, Hammer Mill, and Roller Mill Cost Study
For our case study, we looked at a customer who is an animal feed producer for their local area. They make animal feed for dairy cows, pigs, and poultry with these weekly specifications:
- 1600 tons – 300 micron particle size
- 1200 tons – 500 micron particle size
- 725 tons – 1200 micron particle size
Initial Purchase Price
The initial purchase price includes the equipment itself, along with the main components to run the machine such as soft starters or VFDs. The hammer mill in particular also includes an air assist and baghouse. We included automatic recipe control on the VersaMill® and standard roller mill because of the multiple grind sizes per week. Below is the calculated initial cost for each machine.
- VersaMill® 12X52 Quad Pair: $493,000
- Roller Mill 12X52 Quad Pair: $285,000
- 2-400HP Hammermills: $370,000 Each with Air Assist and Baghouse
Ongoing Maintenance
Ongoing maintenance is another factor to consider in the TOC. VersaMill® and roller mill maintenance includes the cost of reconditioning rolls.
Our Endurance Roll Program can extend the life of roller mill rolls. Ongoing maintenance for hammer mills includes new screens and hammers.
VersaMill®
For this particular customer’s throughput and particle size requirements, we expect a roll change for every six million bushels with a set of Endurance Rolls. This means they would need to change the rolls approximately every 12 months. Including labor, we estimate this maintenance costs $20,000 per year for a five-year maintenance cost of $100,000.
Roller Mill
The roller mill follows an almost identical scenario of six million bushels per roll change with Endurance rolls. The five-year maintenance cost is also around $100,000.
Hammer Mill
The five-year maintenance cost for a hammer mill is only about $43,000. This includes changing the screens every month and replacing the hammer every two years.
Energy Costs
Energy costs are often overlooked in equipment selection but can significantly impact operating expenses. For this study, we’ve aggregated the cost of electricity to 7.9 cents/kWh.
The hammer mill consumes substantially more energy than the roller mills. Within three to six years, these energy costs will exceed the mill’s purchase price. Its five-year energy consumption cost is over $750,000.
Roller mills use far less energy. The standard roller mill’s five-year cost is just over $500,000. The five-year energy cost for the VersaMill® is about $300,000.
Quality of Finished Size
Product quality, particularly in terms of particle size, often hinges on the proportion of material within the desired range. Industries measure this using various methods, typically mesh or micron size.
In a grind, fines (particles significantly smaller than the desired size) can create a less efficient feed and also cause flowability issues in the machine, leading to product plugging. To mitigate this, grinds are sometimes run coarser, potentially reducing product value or yield.
Hammer Mill
While the hammermill effectively processes dairy feed, it faces quality concerns with pig and poultry feed. A 13-screen sieve analysis reveals a significant population of fine particles.
In pig feed, these fines can lead to bridging issues in storage bins, causing feed outages and potentially increasing animal mortality due to stomach ulcers. In poultry mash, the fines are often wasted as birds avoid them, leading to reduced feed efficiency.
Roller Mill
While the roller mill offers a tighter particle size distribution and fewer fines, it has limitations. When grinding corn, it generally becomes less effective below 375-350 microns. This limitation stems from the grinding process within the gap between the rolls. Increasing the roll ratio (relative speed) is often constrained by belt drive limitations.
VersaMill®
The VersaMill® offers the best quality grind. The independent roll speed control allows for higher ratios and increased shear force, resulting in up to 300-400% greater reduction capabilities. This extends the roller mill’s lower limit constraints beyond traditional roller mill limitations.
Additionally, the independent roll speeds enable gentle cracking of larger particles at lower speeds, reducing the production of fines in coarse particle sizes.
Total Cost of Ownership
The 10-year total cost of ownership is highest for the hammer mill grinder and lowest for the VersaMill®. The roller mill and VersaMill® have similar long-term costs, so a customer’s specific application determines the best choice. Contact us to learn more about the VersaMill® and read about it here.
