Improving Shredder Efficiencies

July 15, 2021

When Is It Time to Change Shredder Hammers?

Tom Stanek

shredder hammers

When do you know it’s time to change your scrap metal shredder hammers?  What does it mean to “change” hammers?

Changing hammers refers to both replacing hammers with new, as well as “flipping” or “turning” hammers to another side to expose a fresh leading edge, or rotating hammers to a new position on the rotor.

Change — swap new for used casting

Shredder Hammer change

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February 17, 2017

What’s Needed to Replace Your Shredder Rotor?

Tom Stanek

Shredder Rotor Replacement

Your wear parts have been doing a great job for many tons of production.  After several years, it’s time to replace your shredder rotor.  What are your options and what exactly do you need to plan the job?  How do you start finding a replacement?  Here’s some information and explanation to get you started.

Find your rotor arrangement drawing.  The drawing shows the entire rotor and describes its major dimensions, weight, shaft size and general assembly.  With this drawing, a rotor builder understands the style and quantities needed to build a rotor.

Example Rotor Assembly Drawing (courtesy of PG&H Engineering)

They can estimate materials and general time needed, enabling them to provide you a quote.  You need to describe what it is you are buying. A picture is worth a thousand words.  Here is a rotor template drawing from PG&H if you need to make your own.

Describe your hammer and hammer pin size.  A drawing with some basic dimensions is ideal. If you don’t have one, go to our quote page and download the hammer template you need (such as bell hammer) and use it to describe your hammer.  The rotor builder needs to confirm your hammer swing radius, thickness, and pin hole size.  Provide them hammer pin diameter and length.  We have a template for hammer pins as well.

Get with your operating crew and determine the specific needs at the shredder.  Yes, you need a new rotor, but what else?  Here are the common replacement items for a rotor change out.

Bearing housings

These hold the bearings and attach the rotor shaft to the shredder.  They get worn and damaged as well.  If in good shape they can be renewed.
You should have a spare set on hand and can plan to use them.  If they have yet to be renewed, get them cleaned up and sent out to a shop that can build them up and machine them to restore a secure fit.

Oil seals

Seals keep the lubricant inside the bearings housings.  They are long lasting, but always replace with new during a bearing change.

Rotor bearings

FAG Beargings by Schaeffler Group

Photo courtesy of Schaeffler / FAG Roller Bearings

Generally spherical tapered roller bearings are used.  You should have a spare set on hand.  If you need a fresh set, order early as lead times can vary by many weeks.  Be sure your spare set is well stored and free of minor rust and dirt.  Larger machines have oil cooled bearings, smaller mills may use greased bearings (not needing an oil re-circ system).

Coupling device

A means to connect the drive shaft to the rotor.  You may be able to remove the old one and reuse it, use a spare, or plan on having a new one made by your rotor shop.

Drive Shaft

You will have the rotor out, so it’s the right time to service your drive shaft.  Plan for it.

Bearing Base Plates and Shim Kit

The saddle is the mounting area on the shredder base where the bearing housing sits to anchor the rotor to the shredder itself.  These surfaces are subject to wear themselves.  The bearing housings should wear first, but in reality, both wear.  The saddles will have to be cleaned and ground flat.  The bottoms of the bearing housings will be milled flat in the shop.  A steel base plate is used when you need to make of the difference in height from the wear of these two surfaces.  A shim kit is useful for rotor alignment.  It is a set of pre-cut metal shims to help you adjust rotor height when aligning the rotor drive train.

Thermocouples and Instrument Wiring

Oil cooled bearing generally have a temperature monitoring probe on the bearing oil. Often the probes and wiring will be damaged after years of shredder service.  If they need to be replaced, plan for it now.

Bearing oil piping, hoses, fittings

Similarly, your bearing oil delivery system takes abuse over the years.  You may need to replace piping or use fresh hose.   You might want to get the bearing oil pump & reservoir cleaned and serviced during the rotor change as well.

Bearing bolts

The studs or bolts that hold down the bearings to the saddle base should generally be replaced.  Bolts are made to have a certain amount of stretch.  Once they have stretched and done their job, they don’t stretch and hold quite the same the next go around.  Its a finer point and often, the bolts or studs are often reused.  It’s best if you change them.  Often the threads and nuts get damaged, so a fresh fastening system is good.  After spending so much to  replace the  rotor, you’re are going to cut corners elsewhere in the installation?  Just saying.

You have your shopping list.  Go find yourself a rotor and replacement supplies.   Call you your Original Equipment Manufacturer or one of the replacement builders out there, such as PG&H Engineering.   Contact us if you need some advice.

May 24, 2016

Summer Fire Prevention for Recyclers

Ben Guerrero

Summer is here and the risk of a fire in your scrap feed stock and fluff piles go up substantially.  Summer brings an uptick in yard flow and several holiday weekends.  Many of us have received that call in the middle of the night that you have a fire emergency at the yard.  We all need to remain vigilant and not let our guard down. Here are some simple rules to minimize the chances of that call.

Scrap-Fire-iStock_medPreventive measures to take:

  1. Keep your scrap piles at least twenty feet away from both fixed and mobile processing equipment. Infeed conveyors, loaders, cranes, need clear space from scrap storage piles. Space means access and time in the event of a fire.
  2. Don’t accumulate large feed stock piles. Production schedules that keep intake to a minimum are best.  If you are down for extended maintenance, add fire breaks and gaps to segregate large piles.  Once you shred it, the problem is gone.
  3. Regular housekeeping is needed at the shredder. Excessive material buildup becomes a problem when contaminants hit the piles.  Consider this scenario.  Scrap builds up between your shredder and the motor room over several weeks.  An auto slips by inspectors with a full fuel tank and it ruptures as it slides down the feed chute.  Flammable liquid runs out of the mill and into that pile of build-up right where your important machinery is located.  Your bearings, hydraulic lines, drive shafts, control wiring, or your mill motor won’t be the same if that pile ignites.  Clear what does not belong on a weekly rotation.
  4. Make sure your fire control systems are in place, hoses and nozzles are in good condition, all fire extinguishers checked monthly, and missing items replaced promptly.
  5. Review with your inspectors hazardous materials which can start a fire such as batteries, gas tanks, propane bottles, and other ignition sources. While 99% of infeed scrap is remediated and prepared for shredder, some things get through the inspection process.  Sometimes dressing up the piles of infeed materials received earlier that day can trigger a problem load lurking in the day’s intake.
  6. Make sure all shreds have been run off the conveyor belts and wet down the conveyors belts and area around the shredder. Be sure to look closely at all of the fluff piles for signs of hot spots.  Make it a priority to have the fluff piles at minimum levels especially before an extended holiday shutdown.
  7. Lastly, have a supervisor walk around the processing area prior to shutdown. An early morning inspection can help set expectations for the end of day shut down walk when your team is wrapping up for a holiday weekend.

Have a safe production summer!!

Take steps to be sure this is not you

December 22, 2015

The Risks of Not Staying on Top of Shredder Maintenance

Tom Stanek

Ben Guerrero has penned a story for Recycling Product News ‘The Risks of Not Staying on Top of Shredder Maintenance.’  Survival in times of low markets dictate many cut backs in shredding facilities worldwide.  When you are low on people, finding man hours to tackle even the most basic maintenance is a challenge.  Ben outlines some of the do’s and don’ts in this article.

While it may be ‘preaching to the choir’ for operators, this simple advice should be acknowledged by senior management.  Shredders and non ferrous separating systems won’t keep running without minimum maintenance.  Idled plants won’t start up or hold much resale value if they are ‘put away cold and wet.’   Deferring too much maintenance could lead to larger issues.

Some scenarios to consider, all actual incidents:

  • Failure to clean the motor air cooling system filtration leads to dirt build up in the windings.  Warmer operating days lead to high motor temps, then overheating and a motor fire.
  • The cleaning crew continues to defer cleaning the spillage that slowly builds up between the shredder and motor building.  Your inspectors miss an auto with  fuel in the tank.  Fuel runs out as the auto slides down the infeed chute, it trickles down next to that scrap pile, and there is ignition.  A fire right next to your mill machinery now needs attention.
  • Extending runs times between grate changes saves part costs.  Eventually grate holes are 30% larger than new, the distance between hammer tips and anvils is large, and cream puffs of balled up sheet drop from your stacker instead of dense shred.  Your fluff loads have more metal than you remember.  You check the last 3 months of production records and realize your non ferrous recovery has dropped noticeably.  Ferrous production is up but shipping density is down, zorba volume is down, and so is revenue.  Was it feed stock, weather, or maintenance? Compare the savings in wear parts to the revenue decline.

Grates Its About the BenjaminsWhat’s the best balance? The answer is different for each plant.  Safety and environmental compliance are non-negotiable operating absolutes.  Operating maintenance is not too far behind.  Ideally it’s all the same mindset at your facility, and peak performance and efficiency continue to be the goal of all team members.  Yes, there must be rational tradeoffs between budget, readiness, and acceptable downtime.  Plan in advance to be ready for seasonal or market upticks in volume.  Be sure your facility stands ready to execute for a return to higher production when opportunity arrives.

Find Ben’s article Recycling Product News – Ben Guerrero.

March 11, 2015


Ben Guerrero

Early 2015 is a tough time to be in the shredding business. Scrap prices continue their deep dive while the input side of the business tries to adjust to the change in value.  It may be the sign of a fundamental reset in the value of scrap.  Obsolete scrap volumes may lag for some time until the economics of disposal and transport become clear.  If you are running a shredder on a limited schedule, can you safely defer routine maintenance?

What do we mean by routine?  They are the habitual tasks that are part of best practices.  They are the small things you know are important, but are tempted to defer because of limited run time or available maintenance hours.  And they are normal maintenance expenditures you might be tempted to put off until better markets return.  Skipping what you know works isn’t ‘adapting’ to new realities but a mentality that will cause more costly problems down the road.

Everyone just needs to take stock of their current production requirements and adjust upon facts, not guesses. The plain truth of the matter is the shredder has to be opened and looked at after every production shift.  Inspecting the box is a matter of routine, not tons.  Who has not had a problem in the first part of a production shift? There may be a piece of scrap jammed in such a way it will pop off end caps or bind the rotor during start up.  Inspecting after each production shift helps you plan for regular maintenance and reduces the chances of surprises.

Everything needs to be checked, despite reduced manning and run hours.

  • bolts have to be tightened
  • liners have to be replaced when wore down
  • feed rolls have to be cleaned of scrap and maintained
  • hammers need to be flipped, moved, or replaced
  • check the distance between hammers and grates & anvils
  • Non-ferrous recovery systems need regular checks to be sure they are fully functioning

Grates have to be checked for proper distance from the hammers to be sure you are getting the best density and non ferrous recoveries from your processing.  The anvil to hammer distance keeps cutting and sizing working to ensure efficient throughput in the mill. Many things are checked on each shift that influence how well the shredder performs and keeps production costs in line with expectations.

daily shredderinspectionsPlanning ahead on vital spares and replacement parts cannot be deferred too far into the future.  If you shred, often you will need it sooner than you think.  Rotors, motors, bearings can fail at the least opportune moment.  Ordering ahead of time and using your labor hours in a pre-determined way helps keep overtime and costs level.

In the business of shredding scrap, not everything works out as expected.  Despite economizing on maintenance and repair, you know where you can defer and where you can’t.  Go with the things you know work best. It will save you headaches and money in the long run.




November 12, 2014

Shredder Drives: Keep the Big Motors Humming

Ben Guerrero

Keep your shredder drive motor breathing clean air.  Change out the air filters!  Whether running an electric motor or reciprocating engines in the heat of the North American summer, you need max air flow.   If you have a closed water cooled system, make sure the heat exchanger externals are clean.

Big Motors HummingEven if you have an outdoor air cooled motor, you likely have a filter within the motor enclosure.  Check it monthly if not more.  Motors outside of buildings are often subject to more dust and dirt than those housed in buildings.

If your motor is housed in a building, keep it positive pressured to cut down on dirt and dust.  Many motor rooms have a negative pressure, noticeable when you first open the door.  Dirty intake filters and obstructed vents are the first place to look.  If that doesn’t do it you need to study the situation and find out why your exhausting more air than your drawing in.  Keep in mind the answer if often add more air in, but there is a practical balance for each installation.

Your shredder’s motor protection relay is monitoring stator air temps and trying to keep the motor temp below the point the motor’s insulation suffers most.  To cool the motor, that means it’s turning without load, limiting your ability to shred.  A clean motor and clean filters will make for more effective cooling.

The photo below is from a dirty air cooled motor.  The build up in the stator is combustible fine shredder fluff and dirt.  It’s plugging up the stator section, preventing air flow through the motor.

The motor was in the shop due to a motor fire.  You can guess the cause.?

Filter media can be expensive and a chore to change weekly or monthly.  But it is preferable to downtime and damage.

Dirty Motor Stator

Dirt Clogged Motor Stator

October 28, 2014

It’s All About the Benjamins: Why Worn Shredder Grates Reduce Your Revenue

Tom Stanek

My colleague Ben chuckles when I summarize his lessons by saying “It’s all about the Benjamins, isn’t it.” He laughs, but it’s true — often we lose sight of our goals in different metrics, philosophies, and competing perspectives.

Grates Its About the Benjamins

However, if we think about the goals in terms of money, sometimes things get clearer.

Similarly operators get stuck in a rut and unwittingly shift focus on their shredding goals. These days, cost reduction is a major concern for every company shredding scrap. We’re all doing more with fewer people, stretching maintenance periods, and looking for the most competitive price.

With all the metrics, reports, cost reduction goals, competing priorities of the times, it can change your operating focus. And change how you view shredder wear parts.

Ben has visited a several operations, obviously well run and maintained. They all had their preference for a certain bottom grate and revealed they’ve been able to push the grate well beyond recommended life, saving them money.

Just because you can run a set of grates an extra long -time, doesn’t mean that you should. The loss in shred density and non ferrous liberation may be greater than the cost of replacing the grates on schedule. While saving on wear part costs and reaching your cost reduction targets, are you throwing away profitable zorba & zurich non-ferrous recovery in the process?

We see it as stepping over a dollar to pick up a dime. What does the money say?


K2 RecoveryGrates

Excessively worn grates do not reduce and liberate as well as fresh parts in the shredder box. As you approach the end of grate life, you’ll find grate hole size increases and the distance from hammer tip to grate face increases.

You’ll also see the distance from anvil or cutter bar to the hammer tip open up, reducing effectiveness. When shred density diminishes, so does the recovery rate in your downstream separation system.

Your steel mill consumer doesn’t like the poor shred density, cleanliness, or copper content worn grates yield. Your eddy currents and induction sorters have a tougher time pulling out materials, if they are making it to the separation plant at all. Non-ferrous metal units are lost to your ferrous pile or waste stream.

If worn grates cut your recovery even a 0.5%, what does that mean to the money?

Let’s use very conservative numbers. Running 10,000 GT per month, an economizer stretches his grate change from 65,000 GT to 95,000 GT. He paid $50,000 for the grate set. At 6.5 months to recommended change, his cost is $7692 per month for grates. He went an extra 3 months, so let’s say his grate cost is zero during the 3 months of extended use. In other words, he saved $7692 per month for 3 out of 9.5 months.

Let’s conservatively say once the grates hit normal life, they yield just 0.5% less non-ferrous recovery. The grate holes open up, the clearances inside increase, the hammers tend to drag over the scrap a bit, and cream puffs of tin start dropping off the undermill oscillator.  Recovery is often expressed as pounds of metals per shredded ton of ferrous output.  We’ll use a common baseline of 100 lbs per output ton.

Again, conservatively lets use a drop from 4% to 3.5% non ferrous per shredded ton. It’s likely much higher than that.  Non ferrous units go down from 100 to 95 pounds per shredded ton.  We’ll let you do the final step to find the money, taking your average price per pound for recovered shredded  metals. We’ll just look at the quantity.

  • Worn grates loss is 0.5% per shredded ton
  • 10,000 GT x 100 lbs/shredded ton = 1,000,000 lbs per month
  • 10,000 GT x 95 lbs/shredded ton = 950,000 lbs per month

During that 3 month run, non-ferrous revenue dropped by 50,000 pounds per month for a 3 month total of 150,000 pounds. Convert that to the sales revenue yourself.  3 or 4 containers of shredder metals is lot more than $23,100.

  • The delayed grate change saved $7700 per month for 3 months, or $23,100
  • Loss in non ferrous metal units 50,000 lbs per month, 150,000 lbs for 3 months

Why are we shredding?

Everyone can trim costs each month and do with a little less. But looking at the money gives us a fresh perspective at how we set those interim goals.

At the request of our best customers, we designed in wear indicators to our K2 RecoveryGrates. We just listened to their feedback, “When when the grate is done, we want to know quickly.”

No stepping over dollars to pick up dimes. RECOVERYGRATES

Want more non-ferrous recovery from your feed stock? Our K2 RecoveryGrates can help you get more from what you already have. Need a better non-ferrous recovery system? Give us a call on helping you find the right solutions for your capital budget. It’s all about the Benjamin’s!

October 13, 2014

ISRI Safety Stand Down Day

Ben Guerrero

Our industry association ISRI is calling for all scrap processors to join a major evolution on October 15th:  Safety Stand Down Day.  In the wake of a tragic stretch of injuries in the scrap processing industry, ISRI is urging all firms to demonstrate their commitment to safety in the workplace by taking at least 1 hour during each shift to engage in safety awareness training.

Why should you do this?

  • A stand down is meant to be a major statement to all to call attention to the seriousness of the situation and demonstrate your commitment to safety and safe procedures.
  • You must show commitment from the top.  Emphasize how the company, managers, and employees will take safe operations to the next level.
  • Many well run and well intentioned processors have had serious incidents recently resulting in fatality or major injury.  It could happen anywhere.  You are not exempt.

At a recent ISRI Chapter meeting President Doug Kramer and Executive Director Robin Weiner addressed their concern for 16 fatalities in the scrap processing industry this year.  Analysis supports all could have been prevented by emphasizing employees to follow safety procedures such as lock out tag out, seat belt use, or confined space entry.  Their message: common sense is the key to the success of any safety program not only from employees, but also from the people who supervise them.

Take ISRI up on its leadership to make a loud safety statement October 15, 2015.  ISRI is offering several training guides for use on October 15th should you need them.  Check them out here.


image provided by ISRI

October 6, 2014

Infrared Camera Positions for Shredder Infeed

Tom Stanek

Why use an infrared (IR) camera at your shredder infeed?  They do pay for themselves in short order with more tons per hour and less delay time over the course of a shift.  And there are ways to keep them out of harm’s way.

Damp and wet system shredders produce a fair amount of steam to accomplish their goals for dust control and regulating the mill box environment.  Get the dew point close to the air temp and you have a lot of steam, really obscuring the view of the feed chute.

One solution is the infrared camera to peer through the steam.  The heat from the shredder lights up the view from behind, creating a back lighted view of what’s in front of the heat.  That would be your feed stock in the feed chute.

While you don’t have to see what’s in front of the DFR, it is extremely helpful to avoid jams and underfeed minutes to the mill.  Keeping the feeder rolling and the mill box full is what it’s all about.  Pencil in the total minutes of non productive time with feed issues against the cost of the camera system, and you will find the cost of a camera reasonable.

A direct camera alignment takes in a full heat signature and gives the best camera image.  But the direct mount is also subject to direct damage.  Fortunately new  camera’s are more sensitive and allow for some alternate mounting methods.

View 1 is the direct mount, with full heat ‘lighting up’ the scrap in front of it.  Bright and sharp views, but hard to maintain and service.

View 2 is the reflected side mount.  The heat signature can be bounced off a polished reflective surface and seen by the camera safely mounted to the side.  A stainless sheet with adjustable mount works well.  We’ve heard of commercial flat screen TV brackets working well to adjust the reflector.  The camera is out of harm’s way, but you need a high enough mounting point for the reflector to keep it clear of the scrap moving over the infeed conveyor.

IR Views

IR Camera Positions


View 3 is a side mounted camera.  New IR systems are sensitive enough to present the scrap profile in front of the feed rollers even from a side view.  The camera is very much out of harm’s way, but  you need a tall mount to look over the side of the feed chute.

The side mount is often the easiest mount, close to platform or protective screen, with less cable run, and easy access.  How does it look?  See the video below.   This camera is a FLIR model A300 with 17mm lens provided as a package by Shredder Vision.

February 3, 2014

Scrap Yard Safety on Stairs and Inclines

Tom Stanek

Often with safety in scrap yards, the small things are taken for granted.  The tactile edge on stairways is one of those things.  Adding a slightly raised and well defined edge to the edge of stairs makes all the difference in the world.  They are definitely an improvement to outdoor machinery installations, such as scrap metal shredding plants.

A simple scrap yard solution to increase the tactile edge on stairs and footing on inclines is to add small rebar or flat bar as pictured.  The profile of both edges is small enough to avoid trips, yet tall enough to provide traction to steel grating or stairs.

Traction Bars

Traction Bars

Low cost, easy to install, and easy to maintain.  Adding them to your machinery installation will enhance worker confidence on stairs and inclines.  You need your team on the job, not out with slips and falls.