Friday, January 6, 2012

Hey Grinder Guy, is there a less expensive way to grind shingles? Is bigger better?

Original Post October 1, 2011

            I’m not going to touch the latter, but could you be more specific about expensive? You are obviously spending a lot of money.
            Shingles are made of tar and gravel. They stick to everything and wear metal so fast you can see your money eroding away.
            In my limited shingle grinding experience I can tell you that tips last hours and screens last just days and you better be getting paid a whole lot per ton for the material.
            This is a fairly new and booming industry. There are purpose built machines strictly for grinding shingles and there are shingle packages that can adapt other grinders into shingle grinding machines. Both can process whole shingles into ¼” pieces and bigger is not necessarily better.
In either case, the significant speed of the hammermills create tremendous wear and most machines need some sort of screen on the finish side to bring material to spec.
In addition, the heat generated with this speed needs to be minimized. A lot of water is pumped into the grinding chamber to suppress the heat and control the dust which is created by the high speed hammermill. The air turbulence created forces shingle dust out the incoming and outgoing sides of the grinding chamber and if not controlled is trapped in air filters and will melt and stick to every hot surface of the engine.
Although water is necessary in this situation, in grinding in general, water is not your friend. Ever grind wet leaves? If so, then you know what I’m talking about. In some industries water is used as a lubricant, but most any type of wet material in grinding causes additional wear.
The excessive water use also carries away shingle fines and released oils, that you want to keep, out every small hole and crack in the grinder. They also stick to the discharge belting and are washed away and lost.
Drew Meylan, Operations Manager for C.S. Carey Inc.of Kansas City, KS thinks he has the answer and uses very little water. “I use a sprinkler on the pile,” only for nuisance dust as you may do in a wood grinding operation. C.S. Carey does contract grinding and shredding and uses a Komptech Crambo slow speed shredder with 2” screens for shingles and ends up with 70% finished ½” minus product one pass without using water in the grinding process. The slow speed of the shredder shafts limit his wear also. Current asphalt plants buying recycled product “are paying for two and a half tons of water per truckload,” Meylan says. Every asphalt plant has to evaporate that water before being able to liquefy their product in the process, so Meylan believes he can ship a higher quality product and give his customers a larger volume per load.
Whatever method or size machine you are using, “it all comes down to cost per ton,” says Scott Harrington of Rotochopper Inc., manufacturers of the first shingle specific machine.  If a machine costs twice the price, it has to do twice the volume and the parts and fuel costs can’t increase the cost per ton.
            Shingle material “is gritty and abrasive” says Lori Rheinberger of the Queen of Parts, “this means you will wear out your parts faster.” Rheinberger suggests trying different tips. She stocks tips that have a solid carbide surface, not just a tungsten carbide coating. If you are limited in your selection of tips because of patents of proprietary parts, it is probably going to cost you money.
            So with all this information, how do we reduce costs?
·         Try a slower speed machine if possible.
·         Try different tips. Also, try building up your screens and tips with weld. This does not have to be perfect especially if you are screening to spec. An extra hour out of a tip is probably a 10% savings. All these parts are going into the steel recycle bin eventually anyway.
·         If possible in your grinder, reverse the screens. Each screen will wear at an angle one way and you can get a little longer life just by flipping a screen around 180 degrees.
·         With a high speed machine, try different grinder screen sizes if you use a trommel or similar machine on the backend to make spec product. If larger pieces are blocking the holes in the grinding process and not letting the finer material out, then you are creating additional wear. A larger screen will increase your production and lessen your wear. You will have to compare the yield of finished product to over as each machine and screen size will be different.
·         Control the dust. Air filters are hundreds of dollars and you will change them daily in your grinder and your support equipment.
·         Cooler weather is better. If you can stockpile for a different time of year, the shingles are much more brittle when cold.
·         Use a smooth discharge belt and belt cleaner to capture all the fines you are creating and keep them in the pile. May need a chute to funnel material off the belt into a pile to it doesn’t get carried away.
·         Keep the radiator out of the dust. The radiator will plug resulting in increased engine temperatures and more fuel usage.
·         Keep your source pile as clean as possible. Contamination costs you money on disposal and rejected product. If you screen material, use a Windsifter or Hurrikan on the  overs material to remove paper and plastic prior to regrinding.
·         Limit the speed, heat and fines containment in the grinding chamber.

Here’s a great place to get additional help. The 5th Asphalt Shingle Recycling Forum is in Dallas, TX on Oct. 27-28, 2011. Get more information here- .
Also, the Construction Materials Recycling Association(CMRA) supplies all its members with support and assistance from other members around the Country. Consider becoming a member  .

Please send any grinder questions to or any other cost savings ideas and I will post them as I receive them with credit to the appropriate person.

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