Improving Shredder Efficiencies

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.

 

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.

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.

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.

Scrap Magazine’s recent issue features a story on shredder wear parts.  Wear Part: Makers of Automobile Shredder Wear Parts are Working to Keep Up with changes in Shredder Design, Power, and Feedstock by Theodore Fischer.

High torque drive couplings usually involve a shrink fit.  The coupling is machined with a smaller diameter than the mating shaft.  The coupling is heated 300-400 degrees hotter, expands and can be slipped onto the drive shaft.  It cools, shrinks in diameter, and a tight mechanical fit is accomplished (with keyways or splines as well).

You may have to remove a shrink fit coupling when changing out drive motors or rotors.  Your manufacturer’s rep can get you some advice on the pulling force and strength needed for a successful removal.  Without adequate set up, you’ll bend or snap rods, and be left with hours of time to shed enough heat before you can work on the unit again for another attempt.

1. You’ll need a lifting device and rigging to hold up several hundred pounds of coupling as you slide it off the shaft.
2. 6 to 8 full diameter threaded rods seated full depth in your coupling’s end holes, and a few dozen nuts.  Use grade 8 rod (150 ksi tensile) to give you full strength and minimal elongation.
3. 2 inch thick backing plate
4. 12-20 tons of jacking force.  Hydraulic jack (s) and enough jack stroke to pull off the coupling.  This may require a stub shaft insert if you the jack stroke is less than the coupling length.
5. Torches and heating tips.  Rosebud heating tips of proper size (8 or 10) are important.  Using both propane and oxy acetylene torches is wise.  Acetylene burns hotter and there is limited space to apply torches to the coupling.  Make sure you have enough gases on hand in case you need more than one attempt to remove the coupling.
6. Fire retardant blankets
7. A clean and clear work area
8. Fire fighting gear, a clear work area, and heat resistant PPE for personnel
9. Your safety program may require a hot work permit

The key item is to heat the coupling quickly, so it expands before the shaft it’s mounted on heats up and expands as well.  The difference in temps for allows for expansion.  Also, excessive heat in the shaft can lead to damage of bearings, seals, and other components.

Always let things air cool.  Never cool with water or gases like a CO2 fire extinguishers.  If you have a fire emergency, do what you need to do to minimize loss of property or life.  However quenching with water or anything else would likely damage the coupling or shaft steel.

Now is a great time to pay a little attention to your double feed roll (DFR). 

Your feeding device is one of the most important productivity factors in your scrap metal shredding system. The feeder is tasked with adding feed stock to the shredder at a controlled rate, both pushing it in and holding it back. 

It cannot be effective without traction aides on the roller surface. Lateral bars and teeth welded to the rolls grab and move material and have sharp edges to assist. Edges are key. Rounded off lateral grab bars and teeth just don’t work as well.

Ideally, you have replacement feed rollers on the ground, ready to swap in place or have a slick one piece cast roller you can replace.  Many DFR units do not. You may not have the time for a large scale DFR renewal.

Enter the K2 Weld on Tooth.

You can renew in place replacing lateral bars and adding weld on teeth to the feed roll.  Adding them over a few maintenance shifts can give you the surfaces and edges you need to grab and hold tin, bales, and loose scrap, getting your feed rate closer to new. 

Fight less on the feed ramp, feed more in the shredder.  Give us a call for a set.

It is the holiday season!  We at K2 Castings wish your team the best. To ensure a safe and happy holiday season, take a few steps to prepare for extended shutdown at your yard.

• Lock down and secure for fuel tanks, equipment, and metals storage.  Check your perimeter fencing and gates.
• Ship out shredder fluff and leave an empty bin.
• If eliminating the fluff pile is not an option, wet them down.
• Park mobile equipment  away from potential fire hazards.
• Have nothing stacked against your infeed conveyor.
• Empty out waste oil, and other potential flammable items.
• Run a quick check of the shop and vital areas for potential problems. Make your checks early in the day or week, so corrections can happen before shutdown.

Don’t forget some basic home safety tips that apply to office Christmas decorations as well.

• Fire Safety.Remember to follow a few simple rules to prevent fires at your home over the holidays.
• Do not plug too many things in to one outlet and risk an electrical fire. If you trip a breaker, there is a reason why.
• If using a fresh tree, make sure it is kept watered the entire season. Be sure to take it down as soon as possible after the holiday season is over. Many countries have “Boxing Day” the day after Christmas for a reason.
• Make sure you have a small multi use rated fire extinguisher on each level of your home and in the garage.
• Do not use electrical cords which have been damaged.
• Always turn off all tree lights when no one is home or when going to bed.
• Get rid of wrapping paper and any other potential fire hazards as soon as possible.

Sailors have been known to wish for ‘fair winds and following seas’ as a farewell to respected colleagues.  Shredder foremen sometimes say farewell with “may you never burn up a motor before a vacation week.”  Okay, we made that up.  Shredder foremen don’t use flowery language.  But in the shorthand between those that shred steel for a living, it’s more like a ‘hey, hope you don’t have to use your spare.’  The point it is, those operators that have lost a motor understand it’s the start of a long week.  How do you make sure it’s no worse than a week?  Planning.  Here are the basics.

1. Identify your spare. If you don’t own a spare electric motor, find one.  They don’t stock them at your local Grainger.  There are a lot of used motors out there.
2. Is the spare stored and ready? The internal heaters need to be energized, and someone needs to turn it monthly, especially if it’s a wound rotor.
3. Transport and lift. Many have their motors stored off site.  Get the wheels in motion early with transport to the shredder.  Have the weights and dimensions ready to give to your transportation broker.  How should it be rigged and lifted?  What crane companies and choices are there? What kind of swing radius is available?  Have these details on file so you can line up trucks and cranes in short order instead of making 20 phone calls at the last minute.
4. Mounting: If it’s a direct replacement, be sure you have the tools to unbolt it. You’ll want to check the security of the mounting frame to the foundation once the old motor it off. If you have a loose stud in the foundation, maybe you have time to remove and grout in a replacement. If it’s not a direct fit replacement, you may have to adapt the mounting frame. If possible, you’ve made the new frame early on for the spare.  Have fasteners, wrenches, and shackles, and port-a-powers or know a company that does. If you change the mounting base, the old base may be grouted in place. You’ll need to chip out the old grout, clean the foundation, and have new grout in stock or be sure of your source. Any old grout will not work. It’s very strong epoxy that will not settle or crack. Chipping it out isn’t a simple job. Have the tools to do it or at least a list of them ready when the need arises. Check with your motor vendor or service rep about shimming in the new motor frame base and avoiding grout. The decision will be based on the conditions at the time.
5. Electrical connection. If the spare is not a direct replacement, is the starter, LR tank, and other items compatible? Do you have sufficient cooling air volume for this motor? Will the stator & rotor main conductors match the motor connecting locations? Heavy conductors do not flex well. If you change styles of motor, you may have a major wiring job ahead of you. Do the connecting lugs fit in the electrical terminations? What about the changes for temp RTD’s, RPM monitor, internal heaters? How about wiring in the power factor correction capacitor bank? Any pre-planning and prep you can do here can lessen days of OT electrical rates.
6. Cooling air or water. You may need a new sheet metal exhaust duct or alter the water piping (depending on air or liquid cooling). Be ready to change supply air filters or flush your cooling system if time allows.
7. Coupling connection. Have the tools and parts ready to disconnect the motor from your drive line. Check alignment of the new motor to main dimensions required of your installation. The motor axis and rotor axis should be level and parallel to each other, but not necessarily in line. Your shredder manufacturer and drive line specialist can advise the offset specs.
8. During the change out, find out what may have caused the motor failure. For example, a seized drive shaft universal joint may have caused a motor bearing failure. If you don’t correct that problem, you may have the same motor bearing failure with the replacement motor.
9. Having the plan in place prior to the problem will help you get back on line sooner. It may also let you delegate the initial steps to your acting foreman while you try to avoid cutting short a vacation week. That said, may you never burn up a motor before a vacation week.

There are hammer patterns to fit every type rotor and feedstock situation.  The goal is to get effective production levels while extending the life of your wear parts. Shredder hammer patterns can play a key role in accomplishing these goals.

Spider rotors can have anywhere from 26 to 30 plus hammer positions. Although there are this many potential positions, in the majority of applications it is best in terms of performance and reduced wear parts cost, to use fewer hammers to achieve your goal.  There are not many patterns for a typical 4 arm spider rotor. You can reduce wear parts costs by dropping the number working hammers, using worn out hammers or pin protectors in the dropped positions.  Start, with 2, then 4, dropped working hammers and look at tons per hour and separation.

Reducing the hammer count in a spider rotor has produced mixed results.  Some machines achieved notable production gains, but often produced less dense scrap.  A density change indicates other factors were likely involved that were not controlled or noted.  Maintain grate size, monitor shred density and non ferrous recovery rates to be sure where your gains come from.   Finding your ‘sweet spot” requires a little experimentation and measurement.  If you can maintain density and recovery and use less new hammers, you’re moving in the right direction.  Whatever your combination of working hammers, be sure to weigh and balance your rows.  Spider rotors demand it.

Next time, disk rotors.

FIRE PREVENTION

Summer is here and the possibilities of a fire in your scrap feed stock and fluff piles go up substantially. No one wants to get that call in the middle of the night that your yard is on fire.  Manage your operation to minimize risks at your shredder.

Some precautions to take:

1. Keep your scrap piles at least twenty feed away from all processing equipment. Infeed conveyors, loaders, cranes, etc.
2. Don’t accumulate large feed stock piles.  Process it.  If you are down for an extended period of time for maintenance, add fire break gaps to segregate large feed stock piles.
3. Make sure your fire control systems are in place. Hoses and nozzles are in good condition. All fire extinguishers checked monthly. Discharged extinguishers moved to used tank area for refilling.
4. Make sure there are no trash piles in the yard. Old pallets, Gaylord boxes etc. These all should be disposed of properly on a regular basis.
5. Re-educate your inspectors to watch for hazardous materials which can start a fire. Batteries, gas tanks, propane bottles, all other flammable tanks.
6. Make sure all shreds have been run off the conveyor belts and wet down the conveyors belts and area around the shredder. Especially over a long holiday weekend.
7. Lastly, have a supervisor walk around the processing area to insure there are no hot spots. Make a person in each area also responsible to inspect the areas.
8. Enforce after hours yard security.   Security needs to make night rounds of process areas.  Also, many fires are also intentionally set after hours by “unauthorized” visitors.

Have a safe production summer!!