A clean screen

Screens are an essential part of every material recovery facility (MRF)—operators need to be able to screen and separate containers from fiber as well as old corrugated containers (OCC) from old newspapers (ONP). Most MRFs feature two or more screens in their sorting processes.

Screens have been a staple in MRFs for many years, but technology has changed. Recycling Today connected with Justin Rice, president of Midwest Recycling Service and Sales in Cartersville, Georgia, to learn about trends in screening technology and tips for maintaining screens.

Recycling Today (RT): What are the most common types of screens in MRFs today?

Justin Rice (JR): The most common are ballistics. They are getting popular for the container side of things, separating 2D and 3D materials. Ballistics have taken over the polishing screen’s place in some instances. Ballistics came around because they are more low maintenance, whereas polishing screens require more maintenance. If they get binding or a lot of shredding, it hangs [polishing screens] up. You get a lot more wear on a polishing screen than a ballistic separator. ... I would say screens are pretty much the same as they have been for years, aside from ballistic separators really taking the polishing screen’s place.

RT: In the past five years, how has screening technology changed?

JR: The biggest change is they are just getting wider and longer and bigger to allow more throughput. A lot of screens are well over 100 inches wide. A few years ago, a lot might have been 80 inches wide. Now, I’d say the standard is 100 inches or more in width. You get more material on it and spread it out to give you better quality.

Screens are getting to where they can handle different shapes and different adjustments, such as separating 2D and 3D material and adjusting for efficiency, throughput and quality.

Safety has also improved on screens. You can maintain them without concern about falling through, so that has improved a lot in the last 10 years.

RT: What are the pros and cons to going with a traditional screen versus a nonwrapping screen?

JR: It comes down to the materials analysis that you do. If you get a lot of shrink wrap, you definitely want to invest in a nonbinding screen, for sure. Then depending on the amount of fiber that you are getting, that determines the size and throughput. That would determine how many fiber screens you have. It all comes down to your material breakdown.

Manufacturers also will work with you to recommend the best screen for your materials. Work with your manufacturer to determine what works best for your MRF. It’s important to let the manufacturer know the material you’re running.

RT: What screen maintenance tips do you offer today’s MRF operators?

JR: The main maintenance issues I see are over-greasing bearings, not keeping the shafts clean and not replacing stars or discs frequently enough.

I always recommend cleaning every break. It’s a good rule of thumb and good practice to get into. You can really stay ahead that way. Also maintain the style of bearing—the star or disc—making sure the rubbers aren’t worn. Keep them well-maintained. But that’s a big problem—a lot of people don’t maintain them.

RT: How do changes to the inbound material stream affect screening technology performance as well as screen maintenance?

JR: The material change can be wet, frozen or have excessive amounts of OCC or ONP. It also can sometimes become overburdened with containers. Glass is also a big issue, wearing out the rubber stars or discs at the impact zone, which will make the material not grab and screen as it should. What I’ve seen is that change [to material streams] doesn’t come really drastic.

You can determine changes on the front end of your operation. Put the work in to see what materials do and find out what your community is going to do. You have to learn to adapt the screens.

If you know what could change ahead of time, work with your manufacturer and let them know that in the design of the equipment. When you install your screens, plan for the future material stream and not what’s in the past.

You also want to make sure the design of your screens is accessible so you can get to them easier when material changes. You don’t want them to be boxed in so that you can’t get to them.

RT: What are ways operators can adjust their screens to address changes in the material stream?

JR: You can adjust and have different screen angles, depending on the inbound material you’re running, to clean it up. With adjusting screens, find a happy medium.

It’s easier to make adjustments while you’re in operation rather than taking downtime so that you can see the effect—that way, you can see the consistency of the material without stopping and starting.

Justin Rice is the president of Midwest Recycling Service and Sales. Visit www.mrssinc.com for more information.