Introduction
Manure separation is often an important part of a dairy’s manure management program, so it’s critical that the best equipment is selected 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.
The good news is that many of these technologies have been used in the dairy industry for years, which means plenty of relevant and useful information about them is available.
Rotary Drums are one of the technologies that have been used successfully in the dairy industry. They are also used across a wide range of other industries to separate and/or thicken 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.
Fine mesh screen inside a Rotary Drum.
If you’ve decided that Rotary Drums would best fit your separation project, now it’s time to consider the five following questions before deciding which drum is best for you.
1. Has it been proven in a manure application?
Rotary Drum technology has been in use for decades, effectively screening a wide variety of materials such as fruits and vegetables, municipal waste, aggregates, minerals and different manures. Just because it has been used in other industries doesn’t necessary qualify it for a manure application.
In many ways, manure is very challenging to screen. For any equipment to be successful, it must be able to screen a high solids content material that is both corrosive and abrasive. Some equipment is simply not designed for that.
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.
As an 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 gpm of material. That same machine used in a flume system and screening 5% Total Solids material may be only able to screen 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 qualified manufacturer should be able to supply names and locations of dairy sites that can be contacted and often visited.
2. What kind of drive system does it use?
The ideal drive system requires minimal maintenance with low power consumption. Several drive options are chain, belt, gear and direct drive. Chain, gear and direct drives offer the most positive drive system with little or no chance of slippage.
Chains should be kept clean and lubricated. Keeping a chain clean and lubricated in a manure system can be challenging, as it’s very difficult to isolate the drive system from the manure.
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.
One of the biggest challenges with a direct drive in a manure system is debris. Long fibers, strings, placenta, etc. tend to get wrapped and tangled on the supporting framework on the drive end.
Another option is a belt drive. Belts don’t require any lubrication or maintenance, but 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.
Belt drive.
Belt and direct drives provide the smoothest and quietest operation of any drive system.
3. What style of trunnion wheels are used?
Nearly every make and model of Rotary Drum requires that the drum rest and rotate on trunnion wheels. Some companies use wheels with integral, non-greasable bearings. Since these wheels continuously operate in the wet, manure environment, even the best shielded bearings eventually succumb to the manure.
The drum rests on four trunnion wheels.
Other 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 for 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. If a centralized grease bank is used, the time required for greasing will be minimal. At a minimum, the greasing should be able to be accomplished without the need to remove the guarding.
4. Is it versatile?
Manure consistencies can be unpredictable. 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 with 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.
Perforated plate screen (left) and fine mesh screen (right) produce the best separation.
Screens should also be able to be replaced with reasonable time and effort. Prior to installing any rotary screen, make sure to check with the manufacturer to ensure you’ll have good access to the drum section if repairs need to be made.
5. Is there any kind of cleaning mechanism included?
Screens become plugged with manure, foreign material, debris and mineral deposits, decreasing their ability to screen material and sometimes rendering them ineffective.
Just 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.
CIP system keeps the screen clean.
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 companies can provide machines with a proven track record in the dairy industry and can provide years of trouble free operation.
