KWS Manufacturing

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC

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Plant Name and Location

Boise Cascade
Moncure, NC

General Description of the Application

Boise Cascade Company manufactures a variety of engineered wood products, plywood, lumber and particleboard for the construction industry. The location in Moncure, NC produces plywood. In an effort to decrease waste, wood trimmings are used as fuel for boilers to provide additional electricity for the mill. The wood trimmings are called hog fuel in the wood products industry and consist of every form of wood, from sized chips to long/fibrous strands. The non-uniformity of the hog fuel makes it very difficult to convey effectively using standard screw conveyors with hanger bearings.

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

Torque Arm of Shaft Mounted
Drive is Secured to Trough End

One of the inclined screw conveyors at the Moncure mill conveyed hog fuel from several other conveyors to a surge bin. The inclined screw conveyor was a constant source of maintenance and production issues due to having several hanger bearings in the flow path of the hog fuel. The long fibers of the hog fuel matted together and formed a restriction to the flow at the hanger bearing location. The inclined screw conveyor plugged, causing an interruption in production. Sometimes, the hanger support brackets would fail and shut down the system. KWS provided a long-term solution to the problems and eliminated all the downtime and production issues.

Design Parameters of Application

  1. Product Type: Hog Fuel (Wood Chips & Fibers)
  2. Material Density: 15 to 30 Lbs. per Cubic Foot
  3. Capacity: 1,867 Cubic Feet per Hour
  4. Duty: 24 Hours per Day, 7 Days per Week

Advantages Provided by KWS

Boise Cascade asked engineers from KWS to visit the mill to help solve their problems with the inclined screw conveyor. After reviewing the application, KWS recommended a single piece screw section to span the full length of almost 31-feet. Internal hanger bearings would be eliminated along with any restriction to the flow of hog fuel. KWS also recommended an open-end discharge so the hog fuel would discharge directly into the surge bin. KWS designed and manufactured a 24-inch diameter screw mounted on 10-inch schedule 40 pipe to span the long length with minimal deflection. Since the screw conveyor was located on a 25-degree incline, the flight pitch of the screw was selected for maximum efficiency.

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

Discharge End of Screw is Supported
by Special Hanger and Bearing

Special Features of KWS Design

One aspect of screw conveyor design that is often overlooked is the bending load on drive and end shafts due to the weight of a 31-foot long screw. The single piece screw section weighed over 2,000-lbs. Both the drive and end shafts must be designed to handle the bending load for the life of the conveyor. Engineers from KWS carefully designed the new screw conveyor and selected 3-15/16-inch diameter shafts. The heavy screw section was supported on the drive end by a pillow block tapered roller bearing to relieve the overhung load on the shaft-mounted reducer. A special torque arm trough end was designed for the application.

Testimonial

"The new KWS screw conveyor is a beast, we haven’t had any issues with plugs since we put it in! Thanks to KWS for fixing our problem."

Maintenance Manager – Boise Cascade

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

Old Incline Screw Conveyor was
in Serious Need of Replacement

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

Pillow Block Bearing Supports
Weight of One-Piece Screw

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

Incline Screw Conveyor is Fed
by Two Screw Conveyors

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

New KWS Screw Conveyor
Solved All Previous Problems

Screw Conveyor for Hog Fuel at Boise Cascade Plywood Mill in Moncure, NC - KWS

One-Piece Screw Eliminates
Any Flow Restrictions

Wood Chips & Bark

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