Tub Grinders Evolve with New Features

There are signs of recovery in the grinder market. “With an increase in land clearing activity, we have seen a real resurgence,” says Tom Mitchell, Northeast regional manager, Morbark. “Tub grinders have been a big part of that. Mulch producers and governmental buyers have also played a big role in the upturn.”

When selecting a large tub grinder, capacity and production are key considerations. “Large land-clearing contractors look at the capacity — the diameter of the tub,” says Jay Sarver, recycling and forestry sales manager, Vermeer. “That effectively controls the length of material that you can feed through it.” They also consider the overall weight and the resulting ground pressure.

Horsepower dictates the production rate. But in terms of sizing, there are no easy rules of thumb. “Every material grinds a little different. In addition, the support equipment can dictate how much material you can physically bring to the machine and get into the grinder,” says Mitchell.

To meet the varying production requirements, grinders offer several power options. For instance, the Morbark 1300B offers a choice of 800 or 1,100 hp. “There is a wide range depending upon what the contractor wants to do,” says Mitchell.

There has also been an electronics revolution primarily driven by emissions regulations. “We pay more for horsepower today than we did a few years ago. That is due to increased emissions requirements and advanced electronics,” says Sarver. “But the technology is much more responsive. There are onboard computers on grinders that weren’t available 10 years ago.” The computers control the feed rate, provide engine information and data live via remote and offer several different parameters for the operator to interface with while it is running.

Red River Ranch, Stanton, KY, appreciates the recent advancements in electronics. The company manages three yard waste facilities and has contracts with the Metro Government of Nashville - Davidson County and the Lexington-Fayette Urban County Government. It has four Vermeer TG9000 and three TG800 tub grinders.

“The electronics have been very reliable. Electronic controls just require increased education about how the systems work,” says Red River’s Glenn Salyer. “The productivity through the smart grind is 20% more and the fuel consumption is down with the new electronics.”

Automatic control of the feed rate has dramatically increased productivity. According to Mitchell, a big advancement over the last couple of years is proportional feeding, where tub rotation (feed speed) is adjusted depending upon engine load and how hard the grinder is working with the application.

Options Transition to Industry Standards

While mechanical over-center clutches are still available, the grinder industry is moving toward hydraulic clutches. They have almost become the standard.

“The majority of big machines now have a hydraulic clutch,” says Mitchell. For example, Morbark offers the PT Tech and Twin Disc hydraulic clutches on its grinder models. While more expensive, hydraulic clutches allow self-adjustment, increased durability and remote operation.

All of Red River Ranch’s grinders currently have PT Tech hydraulic clutches. “We have used manual clutches in our rock crushers, but the hydraulic clutches really add a lot of safety and durability because they will not let the operator start with a jam,” says Salyer. “There is really no way to damage that hydraulic clutch other than oil contamination or just a lot of abuse.”

The grinders run by St. Louis Composting also use PT Tech hydraulic clutches. The company operates six facilities around St. Louis, MO, and also does a fair amount of contract grinding, including land clearing projects. It owns a fleet of horizontal, tub and slow-speed grinders, with the tubs primarily used to grind yard waste, logs and pallet waste.

Previous generation models, such as the Morbark 1300A tub grinders, used manual clutches. “One advantage of the hydraulic clutch is operator safety,” says Patrick Geraty, St. Louis Composting. “The operator doesn’t need to get into the doghouse to engage the clutch.” This can now be done from the cab.

Magnetic tail pulleys on the discharge conveyors have also become virtually an industry standard. “Probably 90% of our tub grinders go out with magnetic tail pulleys,” says Sarver. The end customer usually wants product as clean as possible. In addition, metal is worth money. “We have a nail shoot that attaches to the back of our discharge conveyor. As the metal comes around and the magnetic tail pulley captures it, the metal drops down a nail shoot on the discharge.”

Prevent Thrown Objects

Thrown objects have always been a concern with tub grinders, but options exist to minimize the safe working radius around the machine.

Vermeer tub grinders come standard with a two-piece Thrown Object Restraint system. A hinged tub cover covers about a third of the tub, while a deflector plate mounted to the table just above the mill covers about one-third of the up-cut side of the mill. “The two-piece system allows you to work in a lot tighter work zone than traditional tub grinders have to offer without a restraint system,” says Sarver.

The tub cover is hinged and can swing open. “If you work in a land clearing application where you don’t have any traffic, you can swing the tub cover open and provide loading access from either side of the machine,” says Sarver. However, in many cases the cover actually proves beneficial to feeding materials. “When you feed green or wood waste, it actually helps funnel that material down into the middle.” Longer 12-ft. logs run up onto the cover, helping to position the logs vertically and feed them down through the mill.

“The safety features in the Vermeer grinders — the tub shielding, the mill shielding, the thrown object deflectors — are key for us,” says Red River’s Salyer.

Morbark also offers options to minimize the risk of thrown objects. “We offer mechanical and hydraulic covers that will close off the top opening,” says Mitchell. “Typically, those are used when you are shutting the machine down at the end of the job. Then we offer a fixed cover that will help control projectiles on the side where they are most likely to exit the tub.”

Such options are beneficial, but shouldn’t replace proper safety precautions. In business for 15 years, Green Waste Recyclers specializes in grinding for several municipalities. It is on its fourth tub grinder, and currently owns a Morbark 1300B tub and a 4600XL horizontal grinder. While it has a lid for the 1300B, the company also carefully evaluates where to place the grinder on the jobsite.

“Look at your jobsite and set up the safest possible way,” advises George Partlow. “Regardless of what the material is, you can always bring the material to the grinder.”

Consider an integrated grapple

Integrated grapples offer several benefits, including better visibility and the ability to grind with less support equipment on the site. “With longer material, you have a view into the tub to see what is going on,” says Mitchell. “You can manipulate the load to avoid bridging and to make sure that material is gravity feeding to the mill. You get a better sense for what is going on at the mill.”

Approximately 90% of large tub grinders sold by Morbark include an integrated loader. “The integrated loader grapple offers an advantage in any situation outside of re-grinding,” says Mitchell. The only Morbark machine that doesn’t offer an integrated loader is the 1600. “That machine is typically so productive it takes two rather large excavators just to keep it fed.”

Vermeer also offers integrated loaders. “Our cab is about 17 ft. up in the air so the operator has good visibility down into the tub as he is loading the material,” says Sarver. The loader offers 370° rotation. “You can essentially stage material 180° around the machine.”

Whether an integrated grapple is beneficial depends on your operation. “In most cases, contractors are using excavators on land clearing jobs anyway,” says Sarver. “Whether or not the unit has a loader isn’t as important as other features, because you can feed them with the excavators.”

“Integrated loaders do not work in our business model,” says Salyer. “You almost always need two machines with an integrated loader. You need some way to push away, and you need some way to bring the material because you can only have a 20- to 30-ft. radius of reach.”

In many applications, Red River Ranch supports its tub grinder with a single wheel loader. “Our machine of choice is a Cat 966 wheel loader with a 12-yd. light material-handling bucket,” says Salyer. “That machine fits well with the capacity [of the tub grinder]. Depending upon the job, that machine can load the grinder, push the product away and load a few trucks in between. And when we are not using the grinder, we can use the loader for something else.”

“Where I see more applications for a self-contained machine are contract grinding for municipalities, storm cleanup or where there is a designated site,” says Sarver. In these instances, they have a truck and a wheel loader to push material away from the grinder and up to the integrated loader.

“The only way we have ever bought the tub grinders is with the built-in loading systems,” says Geraty. St. Louis Composting typically uses track loaders or wheel loaders as support equipment. “The built-in loading system eliminates an additional piece of machinery, which would have to be an excavator, to feed that machine. It’s an all-in-one package.”

Green Waste Recyclers also use an integrated grapple on its Morbark 1300B. In land clearing operations, it is often paired with a John Deere 644 wheel loader with a high-tip bucket and/or a John Deere 330 excavator.

The case for onboard air

Onboard air compressors are a very popular option for grinders. “It is uncommon to sell a machine without one,” says Mitchell.

“We have air compressors on all of our units,” says Geraty. “They are for keeping the machine clean, blowing out radiators and changing inserts.”

Both of Green Waste Recyclers’ grinders are equipped with air compressors. “They are a must,” says Partlow. These compressors are used to power tools for tool and screen change-outs and to clean the machine every night.

Red River Ranch has a different approach. Only one of its grinders is equipped with a compressor. “All of our operators have their own service trucks and air compressors,” says Salyer. “We found out it is easier for us to maintain a service truck for the guys to carry the tools and wear parts. I don’t think there is a right or wrong approach. We just found out it works better for us. The compressor on that grinder, after so many years, eats so much dust and is exposed to so much vibration.”

Many Red River Ranch operators carry backpack leaf blowers to clean the grinders at the end of the day. “It is hard for an air compressor to spin that much air to blow it off,” Sayler explains. “You need the volume more than you need the pressure.”

Investigate new suspension option

Mechanical suspensions have long been the norm for tub grinders. Now, there is another option.

Vermeer offers an air suspension on its TG7000. “When we built the 7000, we added the air suspension because we wanted a grinder that was high horsepower, high throughput and on as light a platform as we could get so we could travel off road and have good ground stability,” says Sarver. The air ride suspension provides an even load across the wheels so ground pressure is more consistent across the triple axles. With a mechanical suspension, the front axle typically carries more weight than the rear axle due to the weight of the mill and the engine.

“With an air-ride suspension, once the grinder is put in place, the customer dumps the air bags on the grinder,” says Sarver. Thus, you are grinding on the rigid framework. “You are not continually working the suspension as you are grinding.”

Evaluate ground pressure requirements

Tracks are becoming more common on grinders. “We are doing quite a bit with track machines — more on the clearing for the pipeline side,” says Mitchell. “We sell more chippers and horizontal grinders than tub grinders [with tracks], but there is an occasional tracked tub grinder, as well.”

Tracks are offered on all Morbark tub grinders except its largest, the 1600. “Because it is such a big machine (over 95,000 lbs.), it doesn’t lend itself to tracks,” Mitchell points out.

Often, tubs are placed on sites where tracks aren’t necessary “A track grinder is great for tracking down a right-of-way or going long distances. However, if you are going to be taking product out of the field, then usually you have a pretty good landing pad because you need the ability to put trucks on site and load them,” says Sarver.

Consequently, Vermeer offers flotation tires, also known as Super Singles, on its tub grinders. “Flotation tires give you much lighter ground pressure [than standard tires],” says Sarver. Another advantage is that mud often packs between standard dual tires, which creates problems going down the road.

Of course, specific circumstances dictate the optimal choice for your situation. For instance, Red River Ranch prefers conventional duals over Super Singles.

“We had machines with Super Singles,” says Sayler. They are useful if you have weight considerations. But replacement tires are needed on occasion, as the tires can be damaged when the grinders are dug out. “We can get take-off school bus tires that are really good. There are a lot of casings available real cheap.”

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