Types of Log Debarkes: Guide to Advantages and Disadvantages

Types of Log Debarkes: Guide to Advantages and Disadvantages

Wood processors have no shortage of options when it comes to debarking equipment. If processors deal with large volumes of wood, they have drum, ring, and roller (rotary or continuous) debarkers to choose from. If they singulate their process, they may consider a rosserhead debarker, ring, or flail debarker. Many contingencies affect their decision, such as capital costs, and whether they scan their logs. What if their logs are frozen? And what if they deal with species that are difficult to debark? Ultimately, processors consider which debarker will make their operation more profitable.

To help you make the best decision for your mill, we’ve put together this short guide to log debarkers. In it, we describe, in brief, five kinds of debarkers, their advantages, and their disadvantages.

Ring Debarker

demuth ring debarker

Ring debarkers feed logs through a ring of cutters that mechanically strip a log of its bark. Producers who opt for ring debarkers must singulate the feed into these machines. Ring debarkers are more popular with softwood processors than hardwood processors.

Ring Debarker Advantages

  • Low capital costs
  • Can remove bark from difficult-to-debark species
  • Works well for long, straight logs with large diameters

Ring Debarker Disadvantages

  • Must feed them one log at a time, so producers will need to install a step feeder and elevate the debarker
  • High maintenance
  • Less-than-optimal log surface quality
  • Capacity not as high as roller or drum debarkers
  • Can only debark logs within a certain range of diameters
  • Does not work well for short logs (lowers production rate)
  • Does not work well for logs with small diameters
  • Does not always remove bark well from frozen and crooked wood

Chain Flail Debarkers

demuth flail debarker

Chain flails mechanically remove bark by whipping the log with chains. The chains are connected to a small, rotating drum under which the logs pass.

Chain Flail Advantages

  • Low capital costs
  • Can debark frozen wood
  • Can process logs with a variety of diameters and lengths
  • Processes logs quickly

Chain Flail Disadvantages

  • High maintenance
  • High fiber loss
  • Poor log surface quality
  • Possibility of damaging equipment down the line when flails dislodge and get mixed with bark
  • Must feed one log at a time, limiting production

Drum Debarker

drum debarker

Drum debarkers are an older technology developed for processing large volumes of lumber. It is an on-mass system, meaning operators feed multiple logs into the debarker and debark them simultaneously.

Drum debarkers are composed of a large, rotating cylinder (the drum), the inside surface of which is equipped with ridges (“rifters,” “staves,” or “lifters”). As the drum rotates, the rifters lift the logs and cause them to tumble against one another. As bark comes off the logs, it exits the debarker through slits in the drum.

Drum debarkers are not mechanical debarkers, meaning the machine itself does not debark the logs. Friction produced as the logs tumble against each other does the debarking. The rifters may occasionally remove some bark, but they are not designed to cut.

Debarking with a drum can be a wet or a dry process. Newer model drums include a wet pretreatment area where bark, if frozen, is thawed so it comes off.

Drum debarkers have largely been replaced by roller debarkers. Because roller debarkers boast many advantages over drums, we suggest producers consider these machines for large-volume debarking.

Drum Debarker Advantages

  • High capacity
  • Producers can feed in and discharge multiple logs
  • Produces a smooth surface finish in a wet process

Drum Debarker Disadvantages

  • Too often results in high fiber loss, breakage, and end brooming
  • Too much bark left on the logs
  • Does not process small-diameter logs well (or at all)
  • Does not remove frozen bark well or at all without deicing
  • Does not do well with species that have stringy or difficult-to-remove bark
  • High maintenance costs
  • Long downtimes for maintenance
  • High capital and installation costs
  • High energy costs
  • Must deal with effluent in wet process
  • Not easily adjusted; producers are in trouble if they set it up wrong

Roller Debarker (Rotary Debarker)

roller debarker rotary debarker continuous debarker

Roller debarkers are the younger cousins of drum debarkers. Developed in the late ’80s-early ’90s, roller debarkers debark logs using friction and mechanical means. Like drum debarkers, they are an on-mass system and can debark multiple logs at the same time.

Roller debarkers look similar to drum debarkers, but they operate differently. Like drum debarkers, they have a large tube through which the logs travel. This tube, however, is fixed; it is merely sidewalls and a cover. (Smaller roller debarkers may have open tops.) Inside the debarker are a series of rollers equipped with abraders. These abraders act like small hammers that “kick” logs as they pass through, forcing them to move up the side of the debarker until they reach the top and tumble back onto the pile of logs inside the debarker. While this is occurring, all the logs are tumbling against one another. The abraders also cut the log surface to start peeling the bark.

Like drum debarkers, the logs can be kept inside the debarker by closing a gate on the output side of the machine. If the roller debarker has a floor, bark leaves the debarker through slits. If the debarker has an open floor design, bark exits between abraders, which are designed to work as a screen.

Roller Debarker Advantages

  • High capacity
  • Can debark logs with both small and large diameters
  • Can debark frozen logs
  • Can debark species with difficult-to-remove bark
  • Can debarked crooked logs and large limbs
  • Minimal fiber loss
  • High bark removal percentage
  • Reasonable capital costs
  • Easily retrofitted
  • Easily adjusted for species and conditions
  • Smaller footprint
  • No pretreatment needed (and no effluent)
  • Less power required than drum debarkers
  • One operator required
  • Variety of sizes available

Roller Debarker Disadvantages

  • Capital costs greater than those of a ring debarker
  • Installation costs greater than ring debarker
  • Won’t produce as smooth of surfaces as a rosserhead debarker

We’re fans of the roller debarker. We believe this machine has enormous potential to save producers money and to make them more profitable. If you’re interested in learning more about roller debarkers, check out the roller debarkers offered by Biomass Engineering & Equipment, a division of Veneer Services.

Rosserhead Debarker

Rosserhead debarker heads.

Rosserhead (rosser head) debarkers are a common sight at sawmills and veneer mills. These debarkers mechanically remove bark using cutters on a rotating drum, which an arm lowers onto a log rotating on bull wheels.

Rosserhead debarkers enable producers to create smooth surfaces and to shape logs to prepare them for scanning and processing. They work most efficiently when paired with a butt flare reducer, which quickly removes the root flare. With the flare gone, the log rotates better on the debarker and performs better down the line. Removing the flare with the butt flare remover also stops operators from using the rosserhead to remove the flare. Removing flares is not this debarker’s forté.

Rosserhead Debarker Advantages

  • Able to produce smooth surfaces in preparation for log scanning
  • Minimal fiber loss*
  • One-button operation*
  • Can debark frozen wood*
  • Can remove bark from difficult-to-debark species*
  • Works best for sawmills and veneer mills

*Depends on the manufacturer.

Rosserhead Debarker Disadvantages

  • Can only feed one log into debarker at a time
  • Not good for high-volume demands
  • May ring or gouge log surface*
  • High fiber loss*
  • High maintenance*

*Depends on the manufacturer.

Many of the advantages and disadvantages depend on the rosserhead debarker’s manufacturer. This is because rosserhead debarkers have been around for decades, and some manufacturers haven’t adopted technological improvements. Companies such as Veneer Services have updated their machines with the latest technologies to make them as efficient and productive as possible.

Want to know more about our rosserhead debarker? Click here and check out the product page.

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