Troubleshooting Tips from Producers

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Stalks can wrap on the end of the reel

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 fiber 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.

Fiber build up on unprotected header drive

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




Loss of heads over back of header

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.

Dust and chaft 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.

 

Additional protection is needed to keep the stalks or fine fibers 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 fiber 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.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. 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.

  • 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 fibers 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 fibers 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

Hemp fiber build up on header knife

  • 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 fiber 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. 
  • 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.

Fiber wrapping on the final drive shaft

Cleaning

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 buildup 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 fiber out that wraps around shafts etc. Serrated knives and box cutters help to cut off fiber. A hook is useful to reach in beside some beaters, bearings etc. to pull out fiber that may be wrapped around a shaft.
  • The discharge beater (John Deere combine) at the back of the rotor throws the straw out of the back of the machine.

Fiber can build up on bearings of discharge beater

  • 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 fibers shatter and will wrap on and in the links of the feeder chain. Eventually the chain will no longer flex as the fibers 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

Manufactured long hook

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 fiber 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 dented or made a rough spot on the surface. This is enough for the fine hemp fibers 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 fibers from wrapping around the shaft and bearing.

Belt wiper bolted onto end of discharge beater