If you’re a trommel screen owner, you likely deal with a wide variety of material and weather conditions. That means you’re also making adjustments to your trommel screen on a regular basis, to make sure your machine is running as efficiently as possible and that your fines and overs are where you want them to be. There are a lot of ways you can have your trommel set up and how you do that can make a big difference.
To help you configure the efficiency of your trommel screen and get the most out of the material that you’re feeding it, there are four machine settings you can adjust: the angle, the drum speed, the hopper speed and mixing screen sizes. Let’s go through each one.
Adjust the slope/angle
The first parameter to check is your drum’s slope or angle and see if you need to either decrease or increase the angle. Let’s say your angle is at five degrees. Decreasing the angle of the drum to four or three degrees can give the material more time to work through the screen. This can help the material have better separation, since it will be lifted and thrown more. The downside to this is if the material is wet, the mud might make it ball together and impact the screen. If this starts to happen, it’s usually better to let it run through the drum at a faster clip and separate it as best as you can.
The other option is to increase the drum angle. This usually reduces the number of times material hits the screen before it exits the drum. This may lower your output, but it can help keep the screens clean if the material is wet or muddy. The maximum angle you can lift it is seven degrees. Depending on the condition of your material, this may be the better option. Keep in mind that there is a point where the material can get too wet or stuck together and the best option might be to let it dry first.
Increase or reduce drum speed
The second setting you can adjust is the drum speed. Increasing the speed can help break up the material and cause it to separate.
“I like to use a clock analogy to explain drum speed,” explained Duwayne Bonhorst, a product specialist at Vermeer. “For example, you could adjust the drum speed so it lifts the material up to 11 o’clock and throws it to a four or six o’clock position.”
You can also reduce the drum speed, so the material hits the screen with less force. This may not be as productive overall, but it can be beneficial in certain situations.
“Going back to the clock analogy, you could reduce the speed so the material drops to six o’clock,” said Bonhorst. “The downside is this can lower production and may increase spearing of the long material in the fines, but if the material is wet, reducing speed is one way to keep the screens open.”
Increase or reduce hopper speed
The third factor that you can adjust for efficiency is the hopper speed. Generally, a trommel is set up with a typical angle of five degrees and a drum speed of 18 rpm to 20 rpm. As it begins to screen, you want to pay close attention to what the material looks like as it travels down the drum and approaches the overs belt.
“I usually recommend starting the hopper speed slow and gradually increasing its speed until you can see that fine line within the drum where all the fines have been separated,” said Bonhorst.
A slower hopper speed means that the fines material will likely be fully removed halfway or three-quarters of the way down the drum. As you slowly increase the hopper speed, the line of separation will move closer and closer to the overs conveyor belt. You’ll know that you’ve increased it too much when you start to see fines coming out of the overs.
“Some people don’t mind that, but others may want to slow the hopper speed to get the fines to fall through the screen,” said Bonhorst.
In wet conditions, reducing the hopper speed can give the mud more access to the tensioned screens, rather than landing on material in the drum.
You can adjust the hopper speed and drum speed, all from the full-function remote. You can also preload your desired settings with the remote by pressing the auto start button. Take the remote with you into the loader and adjust the machine settings from there. It’s designed for convenience and ease of use to help keep your operation running efficiently.
Mix in slightly larger screens
The final setting you can adjust for efficiency is your actual screens. One way to do this is to mix in slightly larger screens in the first quarter or half of the drum. Vermeer trommel screens are clamped on per section and are efficient to remove so you can customize how you want.
“For example, say you want to add a set of 5/8-in (1.6-cm) screen sections to the first two portions of the drum and leave the rest of the drum at 1/2-in (1.3-cm) screens,” said Ted Dirkx, recycling and forestry sales manager at Vermeer. “As you watch the material gradually screen apart, most of the fines are being processed in the first half. By adding slightly larger screens, you can strike an optimal balance of productivity and quality by taking this route.”
Your specific trommel screen settings will depend on your jobsite and the material you’re processing, but these four parameters are a solid way to test your efficiency and find what works best for your operation.
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