Tuesday, January 30, 2018

Hey GrinderGuy, how do I make more consistent Mulch?

This was not my actual question. The question was how do I stop the spiking of oversize material through a screen on a grinder? It sounded just like most any mulch company in the Country reducing and regrinding.
Even though you are using a specific size screen, doesn’t necessarily mean all material will be less than that screen size. With pallet material or any other kiln dried or dried wood material, each piece needs to be cut and pushed through the screen. If you were using some type of green waste for example, because of the moisture in it, you would get a much finer product and more of a shredded product with that same size screen.
Those large spears getting through the screen are the same as any other Company will get.
Here are a few ideas of how to reduce them:
·         Make the initial grind smaller- This will keep the rotor area more full, and with less open space there is less of a chance of larger pieces being able to fall through the screen.

·         Make sure there is no way any materials can get from the infeed hopper onto the discharge belt without going through the screen. Make sure there are no gaps between the screens or between the screen and anvil/cutting edge.

·          You will get larger sizes when there is the least amount of wood in the grinding chamber. So if the infeed belt of the grinder is stopping and starting a lot it means the grinding chamber is emptying out so the hammermill can pick up speed. With little wood in the grinding chamber, the pieces have all kinds of open screen to fall right out. Slow the infeed enough so that it does not stop, or stops as little as possible and by keeping the chamber full and you will see a major reduction in the larger pieces.

·         Purchase or make Baffled screens. These are normal screens with flat stock welded to the back of the screen at the bottom of each hole row on an angle to stop any long pieces from shooting right through the hole. The spears hit the baffle and hold it so the hammermill can cut it again.

·         Keep the tips as tight as you can to the cutting edge and the screens. If you need to build up the anvil or cutting edge with hard surface more often that is what you need to do. If the tip is as close as ½” to the cutting edges you will get a clean cut. As you wear away the tips and the cutting edge the gap determines your initial size and you will get larger pieces that need cut again. A bead of hard surface across the screens in front of the row of holes will help also. This will make the screens more brittle so use a welder’s knowledge about heat on metals and only do a few inches at a time then move to a different part of the screen.

·         You will hear a lot of people say “Use round hole screens, they make the best product” when the fact is, the difference between a round and square hole screen is the amount of open area on the screen available for wood to go through. It is much less with a comparable round hole versus a square hole.

·         Rotate your screens if possible. The leading hole edge in the screen start to round as they wear. If you can flip them 180 degrees, you will be able to use the other end of the hole with a much cleaner sharper edge. Not all screens have the ability to do this.

·         Grind once instead of twice with a 2” or so screen. Then use about ¾” screens in a trommel or other screen to screen and produce your product. This has its own set of How- To’s but it can be an option.

·         Grind as normal and then screen the product to scalp off any of the oversize spears.

·         Use a smaller screen in the grinder- Not ideal. This would be the last resort.
That should be a good start and you should be able to find something that works for you or a combination that may work for you.

Questions?         Dave Whitelaw                                 grinderguy@askthegrinderguy.com

Hey Grinderguy, what are the proper Grinder Shutdown procedures?

                If you want to protect your investment, then you are asking the right questions. In the Owner’s Manual there is a lot of information including startup and shutdown procedures. You should make a checklist that operators need to complete at the end of each shift. Not only do these make sure your grinder is being taken care of, but you can also use them to figure out some of your costs and maintenance needs by including:
·         Operator Shift Hours
·         Grinder Hour Meter start and end
·         Fuel Usage
·         Engine oil Added
·         Engine Coolant Added
·         Hydraulic Oil Added
By including these items you may be able to determine:
·         What percentage of the day the grinder is actually running?
·         How much Fuel per hour the grinder is using on a particular product?
·         If fluid leaks are increasing?
As for the Grinder itself, or most any other piece of Equipment in a Grinding operation, what should be included on a Daily basis?-
1.       Hook up and pull the grinder out of the grinding area- Leaving it in place is nothing but a fire hazard that can transfer from equipment to equipment or materials
2.       Clean up and remove metal pile that was collected by the magnets on the grinder. Some of this metal may still be hot from being run through the grinder so pile in a safe, debris free area or container is best
3.       Clean Loose Debris from atop the Grinder- All this can be is a further potential fire hazard
4.       Blow off grinder and engine with an air compressor, even with leaf blower if needed. This includes the radiator, hydraulic cooler, fuel cooler, air filter, etc. Pay particular attention to the engine compartment, exhaust manifolds, turbos, etc.  This will keep fire hazards to a minimum and the engine running correctly
5.       Clean debris from rotor area and collection area under rotor and run discharge conveyors to empty the conveyor belts
6.       Fuel and grease Equipment- This allows the equipment more time to cool while you are still nearby just in case something was to catch fire.
7.       Check wear parts and change if necessary. May be too hot to do at the end of the shift but it is the best time to do it allowing more time for rotor area and engine to cool while you are still onsite
8.       If a water truck or water supply is near, hose down the rotor area and underneath the engine or bottom of engine compartment. Spraying water onto a hot engine can crack exhaust manifolds, so don’t do that, but wet down as many areas as possible. Better safe than sorry.
9.       Refer to the Owner’s Manual for Hourly Checklist per specific Manufacturers Recommendations
10.   Fire Extinguishers- How many? Are they charged? What was date of last inspection?
Most of this end of the day cleanup can be reduced by utilizing the wind on a daily basis:
·         Don’t set the grinder back up until morning when you know which direction the wind is blowing
·         Face the Radiator into the wind when you setup the grinder
·         Feed the grinder with the wind blowing dust and fines away from the engine
·         Push material to the grinder from a downwind position or from the side to help protect the support equipment also.
·         Use dust covers and dust hoods on the discharge conveyors. This will not only stop material from blowing off the conveyors but keep material from getting into the tail pulleys, belts and bearings.
·         Use a dust suppression system on the grinder if water is available.
Most all maintenance can be done after the shift so the next work day can get off to a good maintenance free start. Add the particulars of your grinder or shredder to your list and make your operators complete one daily. It not only makes sure your investment is being taken care of, but keeps you informed as to any maintenance items that may need attention and how productive your operation is during the work day.

Questions?         Dave Whitelaw                                Grinderguy@askthegrinderguy.com