Premier Grain
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length grader

Premier Grain's Length Graders utilize a single 17 or 23 inch diameter high density hardened cylinder. We use an environmentally and employee friendly carbonitriding process to surface harder our cylinders to a minimum of 55 Rockwell C (567 Brinnell). The most critical component of any Cylinder Length Grader is the actual care taken with the manufacture of the Indented cylinder itself.  All individual cylinders produced by Premeir Grain have serial numbers which provide a history which includes the date of manufacture, recorded Rockwell hardness and Quality Control sign off.  These Standard Quality Control Checks throughout the manufacturing process insure consistent quality and customer satisfaction. We at Premier Grain strive towards quality, product safety, and social obligations to our employees, our customers and the environment.

Premier Grain has developed a Modular Design which enable the addition of additional cylinder units dependent on the required capacity and number of separations required. A single cylinder can only provide one one length separation, at a typical capacity for the commodity and type or accuracy of the separation. Additional capacity or length separations are accomplish with the addition of extra modules.

Length Grader Length Grader

Operating Theory

The Premier Indent Length Separator has become a standard in grain and seed processing industries due to their higher capacities and lower costs. This Premier Modular cylinder is about 85" long with an approximate diameter of either 17 or 23".  Running through the center of the cylinder is a catch trough and screw conveyor.

The size of the indents in the cylinder determines the length of the material that will fit inside.  Indent sizes are given in a numerical value and are stamped on the outside of each cylinder on the intake end usually near the long seam. The higher the numerical value, the larger the indent or pocket size.  Indent sizes start from a 2.5 (1MM) up to a #44 pocket.  Numerical designations usually correspond to 64's of an inch. (I.E. # 20 = 20/64 DIA.)  

Indented cylinders are designed to lift material the size of the pocket and smaller. The rotation of the cylinder at speeds between 46-50 rpm causes the material that fits inside the pocket to be lifted up by centrifugal force until gravity takes over and causes the lifted product to drop into the central trough.  The angle of the trough can be changed to catch more or less of the lifted product called "liftings".  Material that is not lifted and continues through the machine will discharge out of the "tailings" spout. Material at this point is kept separate thus providing two length separations. 

Trough Control

Trough location is indicated with a pointer and a numbered gauge. The pointer indicates the lifting or forward edge of the trough. The lower the number the higher the amount of liftings picked up and conveyed within the trough to discharge. Sample ports on the lifting spouts allow the operator to check the level of the liftings in the product and then adjust the trough to a higher number for less lifting (shorter), or a lower number for more lifted (longer) product.

trough control


The Premier Modular Indents also have a dumping and clean out position as shown in the above drawing. All cylinder troughs are equipped with grain line blades, (not shown above) that aid in conveying the ‘Tailing’ product toward the discharge end. 

‘Tailings’ is product which remains in the cylinder and is not picked up into the trough. Tailings are the longer material of the incoming product stream. An adjustable dam or ‘Retarder’ is placed near the tailing product discharge. This enables the operator to adjust the depth of the product kidney in the bottom of the cylinder. As the operator raises the retarder, it increases the size and depth of the product remaining in the cylinder.

Cylinder separators are most accurate with a product kidney present, which keeps the indent pockets searching for the proper length material. If a cylinder is starved, (little or no discharge in the tailings) there is a tendency for the pockets to lift longer than desired product.

trough/cylinder control closeup

Available Options

  • Gates Poly-chain Drives
  • Superior Ground Shafting (Standard on Multi-Cylinder Units with Gates Poly-Chain Drives)
  • Lined spouting packages (AR plate or Ceramic Tile)
  • VFD Cylinder Speed Controls
  • Combination Indent Length Grader and Width Grader Cylinders in a Single Machine Package

    Special cylinder plating for extreme wear or corrosive environments

Other options available, call for details.


Length Grader Brochure