Mid-Harvest Maintenance

September 26, 2013 06:00 AM
Mid-Harvest Maintenance

Tips to keep combines cruising all season long

If harvest has hit a rain delay or you’re caught up with the dryer and have a moment to read this, here are a few maintenance matters to keep your combine cruising during the final weeks of harvest:

Check feeder house con­veyor chain tension. If conveyor chains get too slack, they can jump a tooth on one of their drive sprockets when a wad of crop goes in the feeder house. At minimum, running with the feeder-house conveyor chains "crooked" creates a lot of noise. At worst, it bends the crossbars and weakens the chain links; at very worst, they could break and feed the con­veyor chain into the combine.

Even spring-loaded, self-adjusting feeder house conveyor chains can wear and stretch enough to jump sprockets. Keep the springs on self-adjusters at the proper tension. Remove half-links from the conveyor chains as needed to obtain that spring tension.

"It’s better to take time to cut links out of a conveyor chain and get it adjusted to the proper tension than let it run loose enough to jump the sprockets and maybe break the chain," says Jeff Gray, Claas Lexion product coordinator. "Digging a broken conveyor chain out of a combine is not fun."

Check the tension of the clean grain elevator conveyor chain. Inadequate chain tension allows paddles to flex back, reducing their carrying capacity and overloading the clean grain loading system.

Realize that adjusting the tension of the clean grain elevator chain could alter calibration values for yield monitors by changing the way grain strikes the mass flow sensor at the top of the clean grain elevator. Recalibrate yield monitors after chain maintenance.

Replace fuel filters. The tradition of changing fuel filters at the same time engine oil is changed might not keep engines operating at peak power. Modern engine oils, filters and engine designs can extend oil change intervals to as much as 250 hours, while Tier III- and Tier IV-certified diesel engines might need fresh fuel filters every 100 hours. Tier III and Tier IV engines are fussy about fuel cleanliness. Filling from portable fuel tanks can significantly shorten change intervals if stringent fuel cleanliness is not maintained.

Inspect engine air filters. Most manufacturers permit outer air filters to be blown clean with compressed air once or twice before replacement. Inner air filters should be replaced rather than cleaned, unless cleaning is specifically permitted by the manufacturer.

Inspect and clean cab air filter(s). There’s more benefit from a clean cab filter than mere operator comfort. A dirty cab filter can restrict airflow enough to overload and damage the electric motor that spins the cab fan.

While inspecting the cab filter, check to make sure the air conditioning system condensation drain tube drips water on the ground beneath the cab when the AC is running. If that tube is plugged, water will build up in the AC evaporator. Water in the evaporator housing can literally "freeze-up" the evaporator core or create enough humidity in the system that the windows fog over when the heater is on.

Clean the stone trap. If stone traps aren’t cleaned at least every three or four days, the dirt and crop debris that accumulates in them packs so tight that rocks bounce off and then into the combine. Cleaning stone traps daily keeps them full of lightly packed material that "absorbs" rocks and keeps them out of the machine.

"Exercise" the combine’s cleaning fan, concave and cylinder/rotor. If cleaning fan speed, concave setting and cylinder/rotor speed are run for days at a time without significant alteration, it’s beneficial to occasionally change those settings to keep their adjusting mechanisms free-moving.

Adjust fan and cylinder/rotor speeds up and down several hundred rpm. Completely open and close the concave before resetting it to the desired clearance. The same goes for variable speed feeder houses, adjustable deck plates on corn heads, and any other combine component that is adjustable from the cab.

Check the fountain auger in the grain tank for wear. A fountain auger that’s "worn but acceptable" at the beginning of harvest can wear significantly in the first 100 hours of harvest.

"Worn augers increase grain damage," says Kent Hawk, John Deere combine specialist. "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."

mid harvest maintenance2

Flail knives on straw chopper rotors (left) wear on their cutting edge, tip and "wing" on the back of the knife. Fuel sediment bowls show fuel condition. Contaminated fuel can reduce fuel flow through filters and slash power.

Check the flail knives on straw choppers. Worn straw chopper knives don’t chew up crop residue as well, and they greatly increase the amount of power the straw chopper pulls from the engine. Kelly Kravig, CNH product marketing manager, says it’s not uncommon for a straw chopper on a 12-row combine to pull more than 100 hp—even with sharp straw chopper knives installed.

Check all belts. Grab a flashlight and conscientiously examine every visible inch of every belt. Using a flashlight makes cracks and frayed areas more obvious. Major cracks, flaking or obvious burned spots justify immediate belt replacement. Tiny stress cracks or minor fraying on the backside of belts can probably wait until the next rain delay, and—if you’re lucky—might make it to the end of harvest. 

Seat-of-the-Pants Diagnostics

After weeks in the seat of a combine, any odd noise or budding vibration grates on a veteran operator like finger­nails on a chalkboard. Recognizing there’s a problem is the easy part. The challenge is identifying where the disturbance is coming from and what to do about it.

Use a process of elimination to identify the general location of the problem. Start the machine, engage all systems and go to full throttle until the noise or vibration is evident. To pinpoint which system harbors the vibration or noise, systematically turn off the header/feeder house, then the unloading system, then the separator until nothing is running except the engine.

If vibration is most evident when the separator is engaged but fades the longer the machine runs, be suspicious of imbalance due to dust buildup. Dust inside cylinders, beaters and large sheaves or pulleys can fall to the bottom when the separator is shut off. Centrifugal force pins the dust to one spot in the component when the separator is re-engaged, throwing it off balance.

Over time, the dust load will redistribute itself, or the operator can turn the separator on and off at low rpm to redistribute and rebalance the dust load.

Damaged belts, especially variable-speed drive belts, can cause vibration. If a cylinder, rotor or straw chopper has been plugged and its drive belt slipped and "burned" in one spot, that spot is probably measurably narrower than the rest of the belt. Every time that burned, narrowed spot passes around a pulley, idler or sheave, it sends a pulse through the system that can magnify into a significant vibration.

Straw choppers spin at high speed and are very sensitive to imbalance. If a chopper knife comes off, the imbalance can create a vibration severe enough to rattle the operator’s dental fillings. Depending on the design of the chopper and amount of wear on the remaining knives, it is usually recommended to replace two or three opposing knives on the rotor, along with the missing knife, to return the chopper rotor to balance.

Meticulous operators can sometimes detect early signs of bearing failure via routine visual inspection or by monitoring bearing operating temperature with an infrared heat-sensing gun. However, the biggest, most expensive bearings found on cylinder drives, rotor drives and other major components often give subtle audible warning before they catastrophically fail.

Low-pitched howling noises or odd growling or moaning sounds can often be traced to large bearings. Their size and location on large shafts or components often amplifies vibrations into audible warnings of their pending demise. The bearings might look good but exhibit excess free play or unusual heat during operation that justifies a closer look and eventual replacement.

You can e-mail Dan Anderson at danderson@farmjournal.com.

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