Know Where to Look for Wear

August 31, 2012 02:14 AM
Know Where to Look for Wear

Check your combine components to reduce downtime at harvest

The folks at Case IH recently found a promotional film from the introduction of their Axial Flow combines in the late 1970s that bragged their machines could harvest an industry-leading 1,500 bushels of corn per hour.

"Today we’ve got lots of customers running 3,000 to 6,000 bushels per hour," says Kelly Kravig, CNH Product Marketing Manager. "Corn yields have increased, planting rates have increased. The amount of material we’re putting through combines today means customers have to stay on top of wear and maintenance to minimize power consumption and reduce down-time."

Kravig and other harvesting experts recommend farmers envision the flow of crop through a combine, from front to rear, to pinpoint areas of potential wear.

Feederhouse conveyor chains at the front of machines handle every stalk, stem, ear and pod of crop that moves through a combine. Jeff Gray, Product Coordinator, Claas/LEXION, says to "break" the conveyor chain at the master links and check each strand of those hard-working chains for wear before harvest.

"If you break the chain and remove a couple slats, it lets you wiggle each run of chain side to side and get a better idea of how much wear there is," says Gray. "It’s better to replace a worn feederhouse conveyor chain during maintenance than to dig a broken feederhouse chain out of the combine during harvest."

Threshing components are the heart of combines, and obviously subject to wear. All manufacturers offer wear-guidelines for rotor impellers, accelerator rolls, rasp bars and concaves.

"On Gleaners, you want to make sure the rubber on the accelerator rolls hasn’t worn down to bare metal," says John Keller, AGCO Production Performance Manager. "Helical bars, cylinder bars and components that handle a lot of material last longer if they have a chrome wear-layer. Once that chrome layer is worn away, they wear faster and performance deteriorates."

Worn components not only increase damaged grain and magnify losses out the rear of the machine, but increase power consumption and decrease bu./hr. capacity.

Keller cites clean grain conveying systems as an example of how one worn component can compromise overall combine performance.

"A lot of guys put extensions on their grain tank and fill those grain tanks a couple feet beyond the end of the grain tank loading auger," he says. "When the end of that loading auger is buried, it risks overloading the entire clean grain system, all the way down to the shoe. The buried loading auger can’t get rid of grain fast enough, which overloads the clean grain elevator, which overloads the lower clean grain auger and shoe."

Kent Hawk, combine specialist with John Deere, notes that grain tank loading augers with worn flighting exemplify the problems of any worn auger in a combine.

"Worn augers increase grain damage," says Hawk. "As auger flighting wears thin, the diameter of the auger is also reduced, so there’s more room between the edge of the auger flighting and the auger housing. Grain gets tumbled between the sharp edges of the worn flighting and the auger housing. Not only do you get increased grain damage, but it takes more power to move grain when augers are worn."

The enhanced unloading systems on modern combines are designed to disgorge and empty hundreds of bushels of grain in minutes, and therefore prone to accelerated wear. The flighting on the ends of augers in the unloading system, where they transfer grain to another auger, should be checked annually.

"Anywhere grain changes direction or speed as it’s being moved is a potential high-wear area," says Gray. "The flighting on the ends of grain tank cross-augers, and the flighting on the upper end of the vertical unloading augers has to push grain into the next part of the unloading system, and therefore sees more wear than the middle or beginning of those augers.

Auger housings and elevator boots also wear. Kravig recommends using a flashlight and a small hammer to inspect grain conveying housings.

"An auger housing or elevator boot may look okay from the outside, but it may actually be worn from the inside so that all you’re looking at is a layer of paint," he says. "If you can’t visually inspect the inside of a housing or an elevator boot, take a small hammer and lightly tap the outside. You’ll be able to tell by the sound, or if the metal dimples, if the metal is worn thin."

Many combine operators relax a bit after they’ve inspected and done maintenance to the feeding, separating and grain conveying segments of their machines, but experts say straw choppers have become an important component on modern combines.

"Straw choppers influence not only the harvest of this year’s crop, but the beginning of next year’s crop," says Gray. "If you don’t get residue chopped fine enough and spread evenly enough, it can cause problems getting your crop started next spring."

Worn straw choppers not only influence next year’s crop, but slow the harvest of the current crop. Kravig estimated an extra-fine-cut straw chopper handling residue from a 12-row cornhead or 30-foot bean platform could consume as much as 150 horsepower, especially if chopper knives are dull. 

Hawk, with John Deere, compares the performance of straw choppers to eating steak.

"Think about trying to cut a steak with a butter knife instead of a steak knife," he says. "Once a chopper’s knives look like butter knives, you’re going to see poorer shredding, problems with uneven distribution behind the combine, and the chopper is going to eat a lot of power trying to get the job done."

Hawk emphasized that combines, "are a system. From the feederhouse to the straw chopper, each component hands crop material to the next component. If one component is worn and not working optimally, it can compromise the performance of the other components and reduce the capacity of the entire machine."

Most Common Wear-Points on Combines

Some wear-points on a combine are obvious. Some are hidden deep within the machine. According to combine experts, here are five common wear-points on combines. Rate-of-wear may vary between combine manufacturers and combine models.

Feederhouse Conveyor Chains. Feederhouse conveyor chains handle every stalk, ear, stem, pod...and rock...that enters a combine. Bent conveyor chain bars pull chain strands toward or away from each, adding side-stress to their loads. Also look for worn or distorted rollers on chain links. To check wear on conveyor chains, de-tension conveyor chains and use large slip-jaw pliers to compress several links together—excess movement between links suggests it’s time for a new conveyor chain.

Threshing components. Check rasp bars, concaves and other threshing components for wear according to manufacturer’s guidelines.

Clean Grain Handling System. From the lower clean grain auger below the sieves, to the tip of the fountain auger—any worn auger flighting or missing/damaged conveyor chain paddles adds stress to the entire clean grain loading system.

Grain Unloading System. Don’t overlook grain tank cross augers, their troughs, and the sump at the bottom of the main grain unloading auger when inspecting unloading system augers and housings.

Straw Chopper. Choppers with dull knives are power hogs. Dull knives also do a poor job shredding, spreading and spreading residues evenly.

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