Automatic harmony

The process monitoring and control features built into the average auto shredder have improved markedly in recent decades. Initially, these automatic control systems were implemented as a way to optimize shredder throughput, improve the quality of the shredded material and improve shredder productivity.

Those goals remain important, but the number of ways to help achieve them has expanded. Additional considerations, such as safety and energy consumption, have also come into play.

To that end, today’s shredder control systems handle such things as water use and power consumption and offer a networked structure that makes the shredding process safer and the control systems components easier to install and support.

Scott Tauke, engineering manager with Pinnacle Engineering, Cedar Rapids, Iowa, sums up some of the industry’s latest achievements when it comes to automatic controls: “The main goal of any automated system is to increase production and quality and reduce operating cost,” he says. “We are really at an exciting time in the recycling industry, as the markets have forced the processor to think about shredding smarter and allowing the control system to play a major part in this.”

Toward this end, Pinnacle and other suppliers in the industry over the years have introduced more automatic monitors and controls designed to track an increasing number of variables involved in the shredding process. These changes not only have continued to optimize system performance, they’ve also helped free up more of the operator’s time.
 

An established track record

Automatic controls for certain aspects of the actual shredding process have been around for a number of years, helping recyclers to improve productivity and shred quality. Pinnacle Engineering, an independent controls company, has been one of the entities supplying this technology and the associated programmable logic controller (PLC) programs.

For a number of years, engineers explain, shredder control systems automatically have monitored such things as the shredder’s main motor amperage, rotor revolutions per minute (RPM) and main motor thermal capacity and have been able to automatically control the feeding speed of the mill based on those parameters. This monitoring ultimately helped to manage the motor’s power and maintain shredding at the optimal rate to deliver the most tons per hour for the power being consumed.

Bob Jackson, electrical engineering manager for the Wendt Corp., based in Buffalo, New York, says the shredding process itself involves three main functions, all of which on the typical Wendt shredder are controlled automatically by its PLC.

Infeed conveyor speed, feedroll rotational speed and feedroll height adjustments all are designed to occur automatically, Jackson says, based on load feedback from the shredder’s motor and instantaneous monitoring of hydraulic pressures.

“The infeed conveyor and the double-feed roller are variable speed based on the amount of power the main motor is drawing,” Jackson says. The automatic control of these speeds is designed to maximize shredding productivity.

He explains that the motor has to work harder as the volume of material processed increases. Too much material, and the motor risks stalling. Therefore, automatic controls engage at preset amperage levels, temperatures or RPMs to slow or stop the feedroll and infeed processes if necessary.

“You want to put enough material in to maximize the horsepower of that motor, but not too much to where it’s overloaded,” Jackson adds.

Other parameters monitored include main motor thermal capacity, upper and lower feedroll pressures and feedroll height, which all play a role in triggering automatic adjustment of feedroll speed and position.

Jackson says the recipe-based system is initially set by Wendt programmers but can be fine-tuned by the shredder operator using a dozen or so touch-screen controls.

Similarly, Pinnacle offers the Co-Pilot software system as part of its Intelli-Shred portfolio of control and shredder monitoring systems. The company says a key benefit is its ability to produce a better shred by keeping the shredder box full.

Automatic controls also are available to manage and inject the proper amount of water into the shredder box based on motor load, Jackson says. The system can control how water injects and how it drains. Water is added during the shredding process to prevent fires and to keep dust down.

Making the systems even more interactive is the fact that both Wendt and Pinnacle engineers have remote access to their shredder control systems and all of the monitored parameters via Internet connectivity.

“We’re able to access the shredder remotely and can get online with the PLC program,” Jackson says. “We can see what the operator sees and can walk him through diagnosing problems.”

Jackson says the shredder control system ultimately assesses the state of every device in the system and can start and shut each one down if and when necessary.

Preventative maintenance functions also are built into the controls system, and alarms are triggered to remind operators about needed maintenance tasks at certain time intervals or to notify them if mechanical problems are indicated.

At the end of the day, the systems are designed to help operators increase productivity, which itself is monitored based on such parameters as daily average tons per hour and motor run time, Jackson adds.

“The well-run yard can get into 96 to 97 percent productivity, and poorly run yards can be as bad as 30 percent,” Jackson says.
 

Future directions

Jackson and Tauke describe some of the advances in control system design in recent years. While virtually all new systems use some sort of control system to handle aspects of the shredding process, the options available can vary greatly from shredder to shredder, Tauke says.

“Shredding today requires a lot less operator intervention than it did in the past,” he says. “The operator’s duties have changed from total control of the shredder to overseeing the entire process.”

Because the control system takes care of the actual feeding of the mill, the operator has the time to keep track of the material the scrap handlers are feeding to the shredder and the status of the downstream equipment, he adds.

As a related change, Tauke refers to the increased use of containerized pulpits and prewired and prefabricated control rooms that can be installed with great flexibility throughout a yard. He says companies are choosing to move shredder operators from the traditional pulpit location to an office or control room away from the shredder, monitoring the mill via camera.

Skip Anthony, vice president of American Pulverizer Co., based in St. Louis, who has worked with Pinnacle Engineering on dozens of installations, says the containerized controls and prefabricated, drop-in-place buildings are adding a new element to shredder control systems.

“Instead of a large building to house the controls and electric panels, we’re now looking at putting them inside a container that will allow us to place them wherever we want around the system,” Anthony says. These prewired buildings are also far less expensive and simpler to build and install and provide more flexibility for plant design, he adds.

Similarly, Jackson describes today’s method of networking the various control panels using five or six remote enclosures that are connected with Ethernet cables.

“One of the trends is to reduce the amount of startup design and labor,” he says. “Instead of building one monstrous system, we build a whole bunch of smaller systems and tie them together.”

Jackson says the average shredder could include 25 control panels, many of which now can be prewired and pretested.

Tauke also refers to the use of newer controls, such as the company’s Power Management System, that target the shredder’s power usage.

“The newest and most advanced of our control systems are now not only managing the actual plant to shred the most tons per hour, but they are also monitoring the electrical supply to the plant to control peak charges,” he says. “This now enables us to more greatly control the electrical cost to the plant.”

In effect, these new controls enable companies to shred more when the overall energy demand is low and less when it is higher during the day, he explains.

These changes are designed not necessarily in an effort to shred more but to shred more intelligently by operating when the overall energy demand is lower “to make sure we use the cheapest power we can,” Tauke says.

A related capability, he says, is being able to control a shredding plant’s own peak energy use by automatically monitoring real-time power consumption.

“If we want to be in a certain peak window, we can set that, and when we approach that, the shredder will back off,” Tauke explains. The control module is designed to monitor energy use through a Web connection to the power company.

Another advancement, Anthony points out, is the use of a wireless platform (Pinnacle’s Intelli-Shred Wire-less) to monitor certain parameters. For example, the company offers a wireless resistance temperature detector (RTD) to monitor the temperature of the shredder bearing.

“Now we’ve gone to a wireless remote on the RTD for bearing temperatures,” Anthony says. “In the past these were hard-wired and caused a lot of problems.”

Moisture monitoring of the shredding process is another new feature. Pinnacle has recently partnered with Eriez, Erie, Pennsylvania, to add Eriez’s new Moisture Monitor immediately after the shredding process on some shredders.

One purpose of this device is to help modulate water use, since excess water is believed to hinder the downstream sorting process. Therefore, the monitor is designed to assess the effectiveness of the shredder’s internal watering system. Tauke says the monitor basically checks the moisture content of the shred to help fine-tune the internal watering system.

A second advantage is reducing the amount of water sent to the landfill with the fluff, he says. “This secondary advantage is proving to be enough of a cost savings that it is offsetting the additional cost of this equipment,” Tauke observes.

Ultimately, the automatic control systems at work in today’s shredders are combining to offer a new level of productivity for companies and operators.

“Production can be achieved almost automatically because of the controls technology, and the controls can react faster than the normal operator,” Anthony says. “This allows the operator to focus on more things around the area and take care of things that in the past he couldn’t really look at.”

The author is a managing editor of the Recycling Today Media Group and can be reached at lmckenna@gie.net.