Tub Grinder Repair

Repairing Bulk Waste Reduction Grinders and Morbark Chippers

Copyright 2009 by Mike Dougan and Morris Rosenthal All Rights Reserved

EERS Equipment Service

To the right you see a CMI BioGrind horizontal grinder with the feed wheel in the maintenance position. The horizontal conveyor belt brings the waste to the feed wheel or rotor which pushes it into the mill. Hydraulic motors drive both the conveyor belt and the feed wheel. You can see the end of the discharge conveyor below the mill, which carries the ground up material to a pile. The hydraulic systems are all powered by a Cummins diesel engine.
To the left is the top view of the mill in a CBI GrindAll 5060 suspended by chains for bearing service. The bearings are accessed from the sides, and need regular maintenance and greasing, or they'll suffer premature bearing failure in these difficult environments. In this instance, the bearings failed completely and needed to be replaced with factory new bearings. Under normal operation, the mill spins at around 800 RPM and the teeth shred the material until it is small enough to pass through the screen being used. Tub grinders use direct drives for the mill, turning as fast as 2100 RPM, and are ideal for woody type waste, smaller brush, in high volume operations. Tub grinders are frequently used in landfills, industrial bulk waste reduction applications, and even inner city botanical gardens.
To the right is the hammer mill for a grinder which was removed to rebuild the tooth holding blocks and teeth. If you don't maintain the cutting edges, or grinder tips on teeth, the cutters may wear away and the tooth holder can then be damaged to the point that they need to be replaced. The holding blocks need to be welded to the drum mill with a special stainless steel MIG wire, or they may end up flying off the first time you crank up the mill. By replacing the tooth tips as they wear, your grinder will perform better and you'll be saved a costly rebuild. With the hammer mill on blocks, you can also see the main mill bearings with a four bolt cap. On the other end of the hammer mill, you can see the pulley for the belt drive. With large belts costing a couple thousand dollars, it's worth keeping the teeth sharp and reducing the chances of frequent jams. Replacing in time only costs from $10 to $20 per tooth (parts, not labor) so it's well worth keeping up.
Above you see the results of the not maintaining a CMI Megagrind grinder. The oil in the gear box for the feeder wheel was not changed on schedule, if ever, and the resulting sludge achieved a cake like consistency until the feeder wheel was completely jammed and could not advance the material. The bearings went bad, gears were caked with rust, and parts are difficult to find for specialized equipment which often goes out of production after limited runs. Some other equipment serviced includes Morbark Chippers and Peterson Pacific and Vermeer grinders. Environmental Equipment Repair Services (EERS) can completely rebuild tub grinders, horizontal grinders, and other bulk reduction equipment, either on your site or at their shop. Tub grinder repair is usually carried out on the customer site due to the size of these machines. EERS is located in Hardwick Massachusetts and travels through New England and Eastern New York. For quotes, contact Mike Dougan at 413-477-0225.
Above is shown the central shaft of a Gruendler grinder mill which has warped through improper operation - namely throwing a piece of steel several inches thick into the feeder. The Gruendler grinder uses grid electric rather than diesel power to generate 1200 horsepower with two 600 hp electric motors. Proper maintenance is critical on a large grinder like this, where the bearings alone can cost tens of thousands of dollars to replace. To the right you can see the grinder mill disassembled into it's component plates. The hammers are affixed to shafts running through all of the plates, with replaceable teeth. The plates in this instance were cracked and also needed to be replaced.

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