Shake, rattle and roll

Inconsistency is inevitable when it comes to the incoming materials recyclers are charged with handling. It is coming up with solutions for dealing with these inconsistencies that can make or break a construction and demolition (C&D) recycler’s operations.

Two years ago at Mercer Group International, this kind of material inconsistency resulted in hours lost to downtime every day.

Mercer Group International is a family-owned and -operated C&D materials recycling facility (MRF) and transfer station based in Trenton, New Jersey. It processes hundreds of tons of materials a day, recovering plastic, cardboard, wood, vinyl, PVC, concrete and metal. But the facility also processes hard-to-recycle items, like plastic bags and long plastic ribbons, that become intertwined with large wooden boards and sheet metal during separation.

It’s these difficult-to-recycle items, in addition to some other conditions, that led to difficulties in operations at Mercer. For example, when material got wet or cold, it would create sticking issues on the company’s existing screen. In addition, the way the grapple loaded the material onto the screen varied, sometimes resulting in clumps of material that were difficult to pick apart.

These issues together caused a problem that is all too common in recycling facilities: Mercer’s primary screen would jam almost every hour, each time causing the entire line to shut down as employees worked to unclog the unit.

“We would have to shut the line down and spend 15 minutes cleaning it,” Jeff Wilbur, general manager at Mercer Group International, says. “We were almost losing 15 minutes an hour when it blocked up, and we would have to shut the line down maybe six to eight times a day.”

When the jamming became routine, Wilbur decided to seek a change.

New solution

As a longtime customer of General Kinematics (GK), based in Crystal Lake, Illinois, Wilbur turned to the company’s leadership team for a solution.

“Part of the challenge was being able to process enough materials for the day without having the issues that they had for stoppage and the hang-ups that came along with that,” says Dick Reeves, the director of resource recovery for GK.

Because of the type of material Mercer was processing and the demands placed on the equipment, GK Territory Sales Manager Robert Wasilewski recommended GK’s Finger-Screen Vibratory Screener 2.0 to handle the tonnage of large, abrasive materials that found their way through the line during Mercer’s rigorous eight to 10 hours of run time each day, five to six days a week.

The Finger-Screen 2.0 is a new model from GK that features a vibratory action to spread material evenly across the entire deck, while tapered fingers designed in staggered positions are employed to help prevent material bypass. The unit separates materials based on 3D sizing to result in minimal blinding or maintenance needs.

While the Finger-Screen 2.0 features many of the workings of GK’s original Finger-Screen Vibratory Separator, one new feature is the in-tandem design arrangement that offers two alternating trough sections. One rests slightly above the other, providing an initial screening area that separates materials based on size before a constant vibration shakes the items down to the second section for further separation. Wasilewski says the initial trough works to remove any potentially destructive contaminants, while the lower trough is designed to reduce trapping and allow the rest of the downstream equipment to operate more effectively.

The two troughs run out of phase, which means they run on different vibration frequencies, to counterbalance the transmission of loads into the system. Varying frequencies not only move the materials with more efficiency, but also assure that the system doesn’t experience problems with mechanical resonance and breakdowns.

The Finger-Screen 2.0 also utilizes a higher stroke than its predecessor, translating into faster travel rates and more energy into the product to provide better separation and screening. The adjusted level of vibration results in a longer displacement, which moves traditionally difficult-to-screen materials more efficiently through Mercer’s system. The longer displacement allows the unit to push through the elasticity of materials, like plastic bags and other flexible plastics, with more ease, Wasilewski says.

“We’ve doubled the length of the stroke from our traditional vibratory screen,” Reeves says. “With that increased stroke, we get better separation, faster travel rate, it helps with the turnover of materials so we get more fines down below the deck, and also helps the customer through the use of the secondary screen.”

In addition to trying to utilize the existing supports Mercer had in place from the old screen, General Kinematics was able to integrate the Finger-Screen 2.0 with the existing structure eliminating additional cost requirements for a new support structure.

Installation process

Once Wilbur decided on the Finger-Screen 2.0, GK got to work designing and building the unit. GK customizes each machine depending on its application after working with facility owners to assure the system works for the specific types of materials they process. For this application, the GK team took the feedback from Wasilewski and his team into account to customize a workable solution for Mercer’s specific pain points.

“Every system is unique and has its own challenges, and with this one, we actually went a little bit wider and a little bit longer on the length to accommodate these larger, bulkier products that are coming through here,” Reeves says.

Once the unit was built and tested, GK representatives had it installed by late December 2017. After the installation, GK worked with Wilbur to tweak the machine for his particular operations and materials. The speed and stroke of the machine, the conditions of the materials being loaded and the way they’re loaded can all affect a system’s efficiency, so GK representatives observed the operations in real time and made adjustments as necessary.

Once tweaks were made, it was time for Mercer to see how its new screen would fare against its most challenging incoming materials.

Seeing Results

Mercer International was the first facility in the country to implement GK’s newest model of vibratory screener. While serving as the “guinea pig” for new equipment can sometimes be a daunting idea for facility managers, Wilbur says his past experience with GK gave him the confidence to put the screen through its first real-world trial run.

“Knowing that it wasn’t your typical construction and demolition site, this was a great opportunity for the Finger Screen 2.0 to be put in place and utilized,” says Wasilewski.

The leap of faith paid off for Wilbur, who says downtime and clogging have decreased since the unit was installed, while materials recovery has improved significantly.

“We did the upgrade in December 2017, and it’s really helped us tremendously. It’s helped us with throughput because it doesn’t clog up the way our old system used to, and our rear screen has actually helped us create a third more recovery in our fines,” Wilbur says. “Efficiency and throughput have definitely increased. We run an efficiency rate up around 90 percent right now.”

Now, even with inconsistencies in incoming material and standard loading challenges, Wilbur has been able to pull out more ferrous, nonferrous and other recyclable byproducts than before while ultimately reducing the amount he’s sending to the landfill.

“The GK equipment that was put in here is the best we’ve ever had. It’s obviously their latest and greatest machine that they have out,” he says. “I think the dual system works. It helps material get flipped over and eliminates that surfing event with fines and dirt. ... It just doesn’t clog up anymore.”

The author is assistant editor for C&DR and can be contacted at tcottom@gie.net.