Introduction
Manure separation plays a critical role in an effective dairy manure management program, making it essential to select the right equipment to perform the task.
Many different technologies are available for manure separation, and making the decision about which technology is best can be challenging, even for the most experienced dairy manager or owner.
With so many options available, making the best decision can feel overwhelming. The key is understanding how each system works and what it’s best suited for.
Before selecting a manure separation system, consider:
- Separation goals
- Manure consistency
- System capacity
- Maintenance needs
- Material reuse
Many of these technologies have been used in the dairy industry for years, which provides plenty of useful information and real-world insight.
Rotary Drums are one of those technologies that have been used successfully in the dairy industry. Widely used in dairy operations and across industries like food processing and wastewater treatment, they are known for reliably separating solids and thickening materials.
The food industry uses them to separate waste material from fruits and vegetables. Wastewater treatment plants use them for removing debris and larger suspended solids. Dairies use them for thickening manure and creating a “cleaner” waste stream to be sent to a lagoon, spread on fields or used as process water on the dairy.
Rotary Drums excel at creating process water for flush systems, as they can be fitted with fine mesh screens to maximize manure separation.
If you’ve determined that Rotary Drums would best fit your separation project, now it’s time to consider the five following questions to understand how to choose the right one.
1. Is the Rotary Drum proven in manure applications?
Rotary Drum technology has been in use for decades, effectively screening a wide range of materials, including fruits and vegetables, municipal waste, aggregates, minerals and various types of manure. However, success in other industries doesn’t automatically translate to success in a manure application.
In many ways, manure can be challenging to screen. For any equipment to be successful, it must be able to screen a high solids content material while withstanding both corrosive and abrasive conditions; requirements that not all equipment is designed to meet.
Ideally, every manufacturer can and will supply charts and tables to help size the equipment. In the case of manure, sizing is based on the total volume to be processed as well as the solids content of the manure.
For example, a Rotary Drum used to screen 2% Total Solids (TS) manure in a full alley flushed dairy may be able to process up to 500 gallons per minute (gpm). That same unit, when used in a flume system and screening 5% TS material, may be only able to process 200 gpm of material.
Since sizing of equipment is generally specific to a manufacturer or brand, it’s up to them to supply the tools necessary to help you make an informed decision.
Request information from the manufacturer about current and past installations. A reputable manufacturer should be able to provide references and locations of dairy sites that can be contacted and often visited.
2. What type of drive system does the Rotary Drum use?
An ideal drive system requires minimal maintenance while operating with low power consumption. Common drive options include chain, belt, gear and direct drive. These systems provide the most positive drive, with little or no chance of slippage.
Chain and gear drives require regular cleaning and lubrication to perform properly. In manure applications, this can be challenging, as it is difficult to isolate the drive components from moisture and debris.
Similar to chain drives, a gear and sprocket drive needs to be kept clean and lubricated. Both styles can be noisy, especially if operated at higher speeds. Direct drives are sometimes used and work quite well.
Direct drives perform well in manure separation, but they present their own challenges. Debris such as long fibers, strings and placenta can become wrapped around and tangled on the supporting framework on the drive end.
Another option is a belt drive. Belt drives offer a low-maintenance alternative, as they do not require lubrication and are generally quieter during operation. However, they may require periodic adjustments to maintain proper tension. Without proper tension, or when a drum has become heavily loaded, belts have a tendency to slip, and if not corrected immediately, will result in a plugged drum.
Ultimately, belt and direct drives provide the smoothest and quietest operation of any drive system.
3. What style of trunnion wheels are used on the Rotary Drum?
Nearly every Rotary Drum relies on trunnion wheels to support and rotate the drum. Not all trunnion wheel designs are the same. Some companies use wheels with integral, non-greaseable bearings. Since these wheels continuously operate in the wet, manure environment, even the best shielded bearings eventually succumb to manure.
Some designs use a shaft-mounted wheel, supported at each end by a bearing that is physically removed from the material being processed. In addition, this design allows each bearing to be greased and shielded with additional seals.
Greasing the bearings and seals should be part of the weekly maintenance for any Rotary Drum system. Ideally, bearings should be easily accessible, and systems with centralized grease banks can further reduce maintenance time. At a minimum, the greasing should be completed without needing to remove the guarding.
4. How versatile is the Rotary Drum?
Manure consistency can be unpredictable, making versatility an important factor when selecting the right equipment. Rotary Drums can be outfitted with a variety of screen sizes and types. The design of the rotary screen should allow for the selection and use of different screen media.
Coarse particle separation can be accomplished using perforated plate material, while finer separation requires the use of mesh screens. Occasionally, a combination of mesh and perforated plate produces the best separation.
Screens should also be able to be replaced with reasonable time and effort. Prior to installing any rotary screen, check with the manufacturer to ensure you will have good access to the drum section if repairs are needed.
5. Is a cleaning mechanism included with the Rotary Drum?
Screens become plugged with manure, foreign material, debris and mineral deposits, decreasing their ability to effectively screen material and, in some cases, rendering them ineffective.
Like any manure separation system, rotary screens will require periodic cleaning. This can be automated with a clean-in-place (CIP) system or performed manually with a pressure washer. Most manufacturers offer some form of CIP system to keep the screens clean and operating at peak efficiency.
Dairy producers looking for a proven and trouble-free method of manure separation should consider using Rotary Drums to separate solids from the manure stream. Multiple manufacturers offer systems with a proven track record in the dairy industry, capable of providing years of reliable operation.
