"With the old over-center clutch, you really have to be on your toes," he explains. "You can burn up a clutch in a hurry if you have an operator who doesn't pay attention to proper procedures. If you have 1,000 hp and try to jam that hammermill into gear a little quicker than you should, bad things can happen."

The hydraulic clutch takes operator skill out of the startup equation. "You push a button and it engages," says Brandon. In addition, the hydraulic clutch eliminates the regular setting and maintenance required by the over-center clutch.

Keep it cool

"If you watch a grinder run, after a couple of hours, depending upon which way the wind is blowing, the radiator screen will start to fill up with stuff," says Brandon.

The physical size of the radiator screens influence how fast they begin to plug. "We utilize a screen that has a ‘waffled' profile, which increases the available air intake surface," says Peterson's Benton.

Jerry Morey, Bandit Industries, notes, "We provide extremely large radiator debris screens ahead of the radiator. We also provide reversing fans to blow debris from the radiator."

Reversing fans have become popular on many large grinders. "The cooling fan is powered by a hydraulic motor, which periodically reverses to purge material that has collected on the radiator screen," says Benton.

These fans reduce the need to crawl around the radiator screen and blow it out with an air compressor. In some cases, there is a button that can be pushed to manually reverse the direction of the fan and purge debris. Other systems, such as the one from Peterson, purge debris automatically. "The fan motor is controlled by a system that is monitoring all of the operating parameters," says Benton.

Inspect and replace wear parts

"In general, the most common wear items are going to be your cutter teeth and your screens," says Byram. "Obviously, that is where your work is being done."

T&W Grinding & Compost Services recognizes the importance of frequent inspections. The hammermill is inspected daily. "We just stop a little earlier and take care of it at the end of the day," says Wilson. "We check all of the belts and conveyors. We are inspecting the teeth at noon and in the evening to make sure they are tight. Naturally, you check the oil in your engine, water levels and that sort of thing. We keep a good eye on everything."

As a result, the company has experienced no problems with its grinder in the past two years of service. And by handling maintenance and inspections every evening, the company shows up at the jobsite ready to work. "We don't want to mess around the next day getting started," says Wilson. "We like to pull in and go to work right off the bat."

Brandon says contractors with good maintenance programs will even bring their grinders into the shop on a bi-weekly or monthly basis. "They look for cracks and any signs that bearings are getting hot. A lot of guys even carry heat guns to see if there is any heat coming out of a bearing where it shouldn't be," he points out. "It is just attention to detail all of the time."

If a problem is suspected, never continue to operate the grinder. "If something malfunctions on the machine, the operator should shut it down immediately and make the necessary repairs rather than trying to continue the run," says Morey. "Keeping the waste reduction machine in tip-top condition is essential in minimizing operating costs and extending machine life."

Many machines turn the mills at high speeds. "If you break a hammer off, it will get out of balance," says Brandon. "A good, experienced operator will feel that. Something just doesn't sound or feel the same."

Drum balance is important for proper operation. "On a high-speed, rotating piece of equipment, vibration is always an issue," says Byram. Consequently, on some drums, when you replace a hammer on one side, you need to replace the hammer on the other side, as well. In addition, you must be careful to maintain balance when welding on a drum.

Take time for two passes

It may be tempting to try to reduce material into a final product in one pass. You may think you are saving time by avoiding a screen change and regrind time. But that is not how it actually works.