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Combine - Troubleshooting Management - Producer & Industry Experience

After 15 plus years of hemp production in Canada, producers have, through trial and error, developed and identified techniques to facilitate grain harvest. Following are some of techniques that have been identified. 

  • Combines manufactured in the last 10 years will harvest hemp with few modifications.
  • Draper headers are preferred as there is more room for the hemp heads to lay down and feed evenly into the combine. Conventional headers are also used.
  • Proper setting of the combine improves the yield and quality of the grain and reduces wear on the combine. It is important for all producers to experiment with ground speed, concave openings, sieves, wind speed etc.
  • Monitor grain tank for cracking of grain and adjust settings as required.  
  • Adjust the concave to minimize seed cracking.
  • Worn or loose chains such as feeder conveyors, internal conveyors and elevators may cause seed cracking
  • Combine at 15 to 18% moisture or less. At high moisture content, a lot of plant material will be in the sample. The sieves will gum up and require frequent cleaning
  • At low moisture content (close to dry), the hemp stalks shatter. There will be more fine strands of fibre that can create wrapping problems.
  • Too high a fan speed will blow hemp seed out with the chaff and allow a large amount of material in the return.
  • Start with a lower fan speed and gradually increase it until separation of chaff and seed occurs with no seed being blown over the chaffer sieve
  • Closing the sieve tends to direct the air to the rear rather than up, but at the same time tends to increase air velocity through the sieve.
  • Open the top sieve or chaffer enough for good separation (1/4 to 1/3 open, or 3 to 10 mm). This will keep the seed from going over the top and out the back of the combine. Ensure that air lifts the chaff on the sieve with a shaking action conveying the material along.
  • A chaffer opening that is too narrow, coupled with insufficient wind, can result in high seed losses.
  • Adjust the lower sieve depending on the sample seed quality in the grain tank. If too much residue is present in the tank, close the sieves slightly. If the sample is overly clean, seed may be going back to the return conveyor, so open the sieves slightly. A lower sieve setting at 3 to 6 mm will usually be sufficient. Excessive returns result in seed crackage and the overloading of one section of the combine, resulting in high seed losses. If the returns are too high, there may not be enough wind, the top sieve may be too open, or the cylinder-concave is over threshing.
  • No more than one metre of hemp stalk should go into the combine. If plugging or wrapping in the machine happens, lift the header as this will reduce the length of the cut and therefore less material going into the combine.
  • The cutter bar height should be high enough to take in the heads of the crop canopy.
  • The header knife must be kept sharp at all times to minimize winding of fibres on the cutter bar.
  • Remove or drop the straw chopper knives. Most choppers are fixed in the back of the machine.
  • If wrapping occurs around the end of the straw chopper rotor, shields are placed on the edge of the rotor to protect wrapping on the bearings.
  • Exterior rotating shafts and pulleys that may come in contact with stalks should be protected when harvesting varieties that reach the bottom of the frame of the combine.
  • Mechanical drives for the header need to be protected. Factory shields help but the universal joints are usually exposed. These will pick up any fine fibres and stalks that rub by them. Protect below these shafts so the stalks do not reach them. Any opening in front of these drives can allow stalks to touch the shafts and start to wrap. 

When harvesting swathed hemp on a calm day, the dust is very sticky and can easily cause combine fires if not blown off regularly

Fibre build up on unprotected header drive

Stalks can wrap on the end of the reel

On pickup reels, PVC pipe is split and the right length is glued back together over some of the rotating shafts. Wrapping can be reduced by ensuring the reel is as high as possible so it is still able to gently push the heads into the machine.

  • Stalks will catch in the pickup reel and be thrown over the back of the header and will be lost. Constructing a transparent or mesh back on the table will help keep the stalks on the table. A back on the header is more important on conventional headers. Conventional headers are more compact from front to back and have less area to put the stalks under the table auger. This can be a common problem when straight combining standing canola. Commercial shields are now becoming available.

Loss of heads over back of header

  • Leaning crops can fall over the divider board, catching and building up at the end of the header. A wedge has been installed to move the hemp away from the outside couple of guards.
  • Fine fibre can also build up in the guard or under the knife. This can be caused by a dull knife or the spacing of the guard in relation to the position of the knife. If happening at the end of the header, a wedge in front of the guard can help this problem as well.

Hemp fibre build up on header knife

  • The wind direction will dictate which side of the field to combine from. Stalks leaning from the wind will hang up on the end of the header. A bunch will form and let go quickly which can cause plugging. Cutting from the opposite side of the field can help.
  • The fan needs to be guarded so the stalks and leaves cannot enter into the fan or wrap on the bearings on each end of the fan. Stalks can enter the end of the fan and bend the blades. Backing up could puncture or bend the fan housing. Belts, bearings and pulleys driving the fan can wrap with hemp causing damage. The dust and leaves can plug the fan.

    Dust and chaff buildup in fan

    These areas can be protected by shrouding with tin or hanging sheets of plywood or puck board under the body of the combine. Make a way for the air to come from higher on the combine where it is not close to the stalks, leaves etc. Newer machines have a wire guard around the ends and under the fan.

Fibre wrapping on fan bearings

Fibre wrapping on fan bearings

    • Additional protection is needed to keep the stalks or fine fibres from being sucked towards the fan where they can wrap on bearings or inside the fan. The wire mesh is not adequate.
    • Protect the planetary drive shafts at the wheels so fibre will not wrap around the bearings. Covering the drive shaft with PVC pipe is a potential remedy. Hemp will wrap on any exposed shaft if it gets a chance. An exposed final drive shaft to the main drive wheels needs to be protected to avoid wrapping.

Fibre wrapping on final drive shaft


PVC pipe slightly bigger than the shaft is cut lengthwise. The split pipe is then placed over the shaft and rejoined by gluing or using duct tape. The pipe is made shorter than the shaft. A larger pipe that fits over the first one is also split and put over the first PVC pipe. The two are extended so they are tight to both ends of the shaft.

PVC pipe on drive shaft held by duct tape. Drive shaft turns inside the PVC pipe

  • The two pipes are then wrapped with duct tape to make them secure and cover the entire shaft. The pvc pipe does not need to turn and should be loose on the shaft. If wrapping does occur, the tape can be removed, pipe slid back to expose the wrapped shaft.

    Fibre will wrap on drive shaft if duct tape fails. Fire could occur.

    The Case IH main drive for the combine comes down the left side of the combine behind the drive wheel. The pulley, bearing and belt should be shielded on the bottom with a mesh or material that will not allow the hemp fibre and stalks to get near the drive. Under the combine, some of the new machines have a wire shield to keep material away from the

    Caged drive shaft on Case IH combine. Additional shielding required.

    from hemp going thru the wire mesh Fine fibres and stalks will still go through the wire cage and catch on the turning drive shaft. Cover the drive with PVC pipe to reduce wrapping. Hanging plywood or puck board under the combine in this area will also help protect the exposed shafts.

  • The Rotor Drive can wrap if material rides too high up in the concave. The shaft is very hard to reach. A rod with a hook on it helps to pull out the fibre. Cutting less height will help reduce the incidence of material wrapping on the shaft/bearing. Producers will check the bearing regularly. Carry water and if need be wet it down regularly to keep fibre soft and reduce the chance of fire.
  • Inspect the machine for belts, pulleys, drives that are low on the machine. Protect electrical wires, pulleys and belts from catching on standing stubble.
  • Puck board or similar sheeting can be used to protect the bottom of the combine to keep fibre from catching on the bottom of the machine and protecting belts and equipment like the fan.
  • Do not back up. Standing stalks can pierce the metal or pull off wires or jam stalks into low moving belts.
  • Duct tape is a hemp farmer’s best friend. Use Duct tape to cover any bolts, controls, shafts that are exposed that may hook hemp fibres. The fine hemp fibres can catch, build up and eventually cause a problem or potential fire. The duct tape makes the bolt smooth so the fibre will not catch and will pass over it.

    Use of Duct tape

  • While emptying the hopper each time, do a walk around the machine checking for wrapping on various catch points on the machine like axles, bearings, and inside the machine.

When harvesting high moisture hemp, regularly clean out the corners and areas where hemp grain builds up in the hopper when it is emptied. This will reduce the risk of these areas heating. This small amount can lead to the build up of pathogens ( e.g., e coli, streptococcus, etc.) that can contaminate or be a source of infection for the whole bin.

  • Clean off machine regularly. Do not let hemp dust build up especially in motor area and filters. Dirt and dust build up on the combine increases the risk of fire.
  • Use a leaf blower regularly to remove dust build up anywhere on the machine. Carry a fire extinguisher and have water available in the field.
  • Fires have been attributed to static electricity starting a fire where dust buildup can occur. Drag a chain to help reduce static electricity.
  • Manufacture a good hook that will fit into areas to pull the fibre out that wraps around shafts etc. Serrated knives and box cutters help to cut off fibre. A hook is useful to reach in beside some beaters, bearings etc. to pull out fibre that may be wrapped around a shaft.

    Manufactured long hook

  • The discharge beater (John Deere combine) at the back of the rotor throws the straw out of the back of the machine.

    Fibre can build up on bearings of discharge beater

    The speed of the discharge beater seems to determine if there will be wrapping. Increase the speed of the beater as much as possible. A high speed kit is available from the company or sometimes a larger pulley is installed to speed it up more than the factory part. Shielding on the front side of the beater may be needed to help keep the fibre from wrapping on the bearings. If wrapping happens often in the same area of the beater check the surfaces for a rough area. Something like a rock may have dinted or made a rough spot on the surface. This is enough for the fine hemp fibres to catch on and start wrapping.
  • A “wiper belting” has been installed onto the John Deere rear beater. Heavy belting is bolted onto every second beater blade. Care is taken to make them all the same size and the same bolts are used so the balance of the beater is not affected. This “wiper” helps keep the dry fibres from wrapping around the shaft and bearing.

    Belt wiper bolted onto end of discharge beater

    Belt wiper bolted onto end of discharge beater

  • Straw when it exits the combine will catch and hang on any rough spot that it can. The hexagon nut heads holding the back hood together is enough to catch straw. Large bunches that hang out of the back of the combine. These will not cause any operating problems but are a concern from how they look. These can be eliminated by covering the bolt heads with duct tape or silicone caulking.

    Fibre will catch on bolt heads

  • Straw Choppers for John Deere combines should be swung away or removed if needed.

    JD straw chopper swung away so it is not operational

    Machines like Case IH combines have internal straw choppers that cannot be removed. The knives should be lowered a low as possible or removed. The chopper rotor should turn as fast as possible.

    Fibers can wrap on end of Case IH straw chopper. Check often.

    Wrapping can occur at each end on the bearings. Shields can be placed on the front side of the rotor to protect the bearings from coming in direct contact with the hemp fibre. Check often.
  • Conveyors are recommended for grain transfer. Use low sloped transfer augers if available. Augers should be operated full and at a slow speed to reduce potential grain cracking and dehulling.
  • Older John Deere combines (9600 series) need some modification to harvest hemp. The fine fibres shatter and will wrap on and in the links of the feeder chain. Eventually the chain will no longer flex as the fibres are compacted into the joints. To make the combine work, producers replaced the chain with a rubber mat. Chains are affixed to a heavy rubber mat. The end overlaps so the mat can flex and stay tight. A few slats are bolted on the surface to give some traction to carry the hemp up the feed housing. Some believe the speed of the chain is too slow so it gives the hemp a chance to wrap in the links. Problem does not seem to exist on newer machines of any color.

    Belt manufactured to replace feeder chain of older John Deere combines

  • It has been found that there can be less trouble throughout the machine especially older combines, if the feeder housing is narrowed down. Metal plates 8 to 10 inches wide similar to the one in the middle of the photo are affixed on each side of the feeder housing. This forces the grain and straw up the center of the combine keeping the hemp fibre away from the edge of the combine where the risk of wrapping of bearings is reduced.

    Metal plate on pick up is bolted onto each side of the feeder housing to make it narrower

  • Changes in crop conditions often occur during the day. Frequent checks and readjustments must be made in the field.
  • After a killing frost, the crop will dry down rapidly. Be prepared to combine before it gets too dry.
  • Trucks should not been driven in the hemp field.  Hemp wraps on anything that moves.
  • Ensure machine insurance is valid and up to date.