Complex machinery requires certain procedures and considerations to be in place in order to protect the safety of those working with and around that piece of equipment. Horizontal grinders are no exception, and in fact present operators with a few special scenarios to address when drawing up and implementing a safety plan.
Dale Messenger is product safety engineer for Vermeer, an equipment manufacturer based in Pella, Iowa, that designs products for the construction, forage, landscaping, mining, organic recycling, rental, tree care, wood waste and other industries. Vermeer designs horizontal grinders to process organic material on land-clearing, municipal waste and composting operations. Messenger has been with the company for 24 years and in product safety for 15 years. In that time, he has thought a lot about the specific safety concerns that affect operators when working with horizontal grinders.
Make it mandatory
“When we talk about safety features, we do not make safety features optional. If you build a horizontal grinder, all the safety features are going to be there,” Messenger says. Operators should look for safety features such as proper guard rails, walkways and a method to keep thrown objects within the machine as much as possible.
“Anything that needs power transmission parts should be adequately guarded as a safety feature,” Messenger says. Most equipment manufacturers provide adequate guarding for power transmission parts, such as belt drives, pulleys and drive lines.
“We also provide access systems, meaning steps, grab handles, guard rails, walk ways and ladders.” Messenger says access systems should be provided for all areas that require routine maintenance by an operator, such as fluid level checks or lubrication or regular maintenance that must be done on a weekly basis.
“We feel horizontal grinders should have some means of reducing the distance of thrown objects, because grinders, due to their rotating hammer design, ultimately can throw product, and we want to limit the quantity and distance that the product is thrown,” he says. “Vermeer has its own strategy, which is multi-faceted. First, our grinders are designed so that the hammer mill rotates in a manner that it cuts material in a downward direction versus an up cut. If you up-cut something and it throws material, it is our opinion that it can be thrown further than if you are down-cutting and it would have to bounce and somehow get off the end-feed conveyor. So we have a down cutting motion of the hammermill. The second item is that to enhance the feeding of a machine, in addition to a moving end-feed conveyor we also position a feed roller on top of the end-feed conveyor. This also is used for feeding material into the hammer mill. The feed roller acts as a barrier that reduces the amount of material that exits the machine.”
Hitting the Nail on the Head
Screen USA Inc., Smyrna Ga., a provider of screening equipment, including trommel, shaker, and starscreens, recently introduced a small horizontal wood grinder specifically geared for small volume applications.
The company’s Hammerhead grinders are being marketed to composters, landscapers, landscape supply houses, utility companies, municipalities and mulch manufacturers.
“It’s not a stump grinder,” Rick Cohen, owner and president of Screen USA, says. “It’s strictly for grinding pallets, brush, and wood 9 inches to 10 inches [in] diameter and smaller.
Screen USA, which was founded in 1973, has built its reputation on manufacturing niche products for the screening industry, and Cohen says the Hammerhead grinder is a niche product for the grinding industry. It is the first grinder offered by the company.
“We’re trying to cater to customers who have been asking for a horizontal grinder, but did not need the huge $400,000 to $500,000 grinders,” he says.
The Screen USA Hammerhead is offered in a 160 hp model and a 240 hp model. The machines come standard with Flexxaire reversing radiator fans to help prevent overheating and clogging. It also features a variable speed feeder and is wide enough, at 4 feet 5 inches, to handle pallets. A radio remote control and magnetic head pulley are standard.
Cohen says the unit is extremely portable and can be pulled behind most small dump trucks or utility trucks. “You can take it almost anywhere and set it up in five minutes and be ready to grind,” he says.
“We don’t have many competitors because everybody is making larger grinders. We decided to promote the smaller grinders with a price tag that landscapers and composters can afford,” Cohen adds.
The manufacturing of colored mulch appears to be a hot market for the Hammerheads, the company adds. The grinders come equipped with an optional mulch colorizer that allows customers to color their mulch.
More information is available at www.screenusa.net.
For material that exceeds the width of the feed roller, Messenger says Vermeer provides a system of barriers along the machine designed to keep material from flying out of the grinder. “We provide what we call a flying object protector, which is a cover and a series of rubber curtains that hang over the machine and act as a barrier to knock down product that has been ejected by the machine,” Messenger says.
“It is important that a machine be under the control of an operator at all times, so that he can stop and start it as needed,” Messenger continues. “With a remote control, the operator can be running the loader, whether it is a mobile loader or a grapple tie-type excavator, [and] he can be running the grinder while working with the loading machines. Like most manufacturers, Vermeer is a strong promoter of safety signs and having the safety manual attached to the machines so that it is readily available to the operator ” adds Messenger.
While a machine is running, operators should know who is coming up to the machine or who might pass by the machine. The operator needs to control the jobsite for other people, Messenger says. “That means keeping them out of the thrown object zone, which can be done by shutting the machine down and informing them that they need to leave the area or put up safety tape or cones to identify that area for other people,” he adds.
The end-feed point on a horizontal grinder has the highest potential for material being ejected at a very high speed “to the point of it penetrating the windows of a loader cab if you were driving by at the wrong time,” says Messenger. It is important for the operator to stay away from the thrown object zone when operating that machine. Operators should never walk in front of the machine without first shutting off the end-feed, Messenger explains.
Daily and weekly maintenance also is imperative to running a safe job site. Horizontal grinders include a rotating hammermill that reduces the size of the raw material. “If daily maintenance is not performed on that drum and its components like the bolts that hold the cutting tips on and balancing plates that are rotating, the risk of throwing these items out of the machine increases,” he adds. “Equipment manufacturers provide a maintenance schedule and instructions with each machine and highly recommend that operators follow those instructions to keep their equipment well maintained.”
“I believe poor jobsite setup or control is probably one of the most common safety mistakes,” Messenger says. There are a number of issues that need to be considered when setting up a jobsite. If any of those tasks are preformed incorrectly, the safety of people working on the jobsite could be affected.
Messenger says one of those tasks is looking at overhead clearance, especially concerning power lines for loading equipment or unfolding conveyors on a horizontal grinder.
“You also need to take into account the prevailing wind direction because grinding is a dusty environment, so the direction of the prevailing winds is important in how you set up the machine, not only as an operator but for the consideration of your neighbors as well,” he adds.
Operators also want to control who has access to the site while machinery is in use.
“Some municipalities will allow the general public to have access to jobsites so they can bring in their trucks and unload material, and if they get close to the machine it can put them at risk,” Messenger says. Jobsite setup should include considering who has access to roads leading to the worksite and who can be at the jobsite when equipment is running or being moved.
Inspect raw materials
Raw material should always be inspected before being fed into a machine. Operators should be aware of what type of material the grinder they are using is designed to handle and not wait to hear or see something wrong from the machine.
“If the machine is designed, as ours are, for organic material, a common mistake is to not inspect the raw material pile for chunks of metal, steel fence posts, rocks or other types of contamination,” Messenger says. Then, operators must “wait to see sparks fly or hear the machine grunt.”
Proper training is important to prevent an accident such as feeding steel fence posts into a grinder designed to handle organic material.
Training can be provided by the company owner. Many equipment makers also offer training programs.
Because horizontal grinders typically are large machines, operators and maintenance workers can be on the machine and out of site. Messenger recommends operators be aware that some manufacturers provide a control system with an audible alarm and a time delay that occurs between a start-up command and the machine starting to move, which are designed to give personnel enough time to move away from the grinder.
The author is assistant editor and can be contacted at firstname.lastname@example.org.