Conveying System for Wood Chips

General Description

Pan Pacific Products is North America’s largest producer of fiberboard stiles and rails. Medium Density Fiberboard (MDF) stiles and rails are the vertical and horizontal structural elements in a hollow door. Stiles are the vertical components, and rails are the horizontal sections at the top and bottom in a hollow door. The stiles and rails are secured with door panels on each side, giving the impression that the door is solid.

Pan Pacific Products has up to 1,000 tons per day of green pine chips delivered by truck. The chips are then discharged onto an incline belt conveyor, pass through a magnet, and then go to a chip washing system that removes foreign materials before the chips are stored. Washed chips are then pumped into the refining system before going to a drying process. The forming and pressing processes follow the drying stage. The final stages of the process are sanding and cutting the boards to size to meet customers’ specifications.

The facility has undergone tremendous modifications and upgrades since moving to a new location in Broken Bow, OK. For a recent upgrade, the plant needed a way to deliver undersized chips back into the process from outside storage piles. Using a front-end loader, the chips would be loaded into a hopper and ready for the process on demand. The chips would then be elevated vertically using a bucket elevator before being conveyed directly into the drying process.

Design Parameters

1. Product Type: Wood chips
2. Material Density: 15 Lbs. per Cubic Foot
3. Conveyor System Capacity: 267 Cubic feet per Hour
4. Duty: Intermittent

KWS Advantages

The KWS engineering team conducted multiple site visits to ensure the new conveying system would fit within the constraints of the existing equipment and current plant layout. KWS engineers worked closely with the general contractor selected for installation throughout the entire process. KWS provided a full set of Autodesk Inventor 3D models and 2D drawings during the review process to check for design and interference issues. Together, we were able to make any minor adjustments to the design to ensure downtime of the plant would be minimized during the installation.

KWS Special Features

A hopper with twin-screw feeder was used to store and discharge the wood chips. Two counter-rotating, stepped pitch screws meter the wood chips evenly and eliminate bridging in the hopper. The twin-screw feeder is fitted with independent gearmotor drives for complete redundancy. Should maintenance be required on one drive, the plant can still remain operational with at least half capacity. Independent drives also reduce maintenance and downtime due to the elimination of chain and sprockets or spur gears.

The twin-screw feeder meters wood chips to a heavy-duty centrifugal-type bucket elevator. Because the wood chips are moderately abrasive, the elevator boot, inlet spout, head, and discharge sections were fabricated from heavy gauge steel for longer life.

The belt and buckets were carefully selected based on the application to provide a long-lasting system and avoid maintenance shutdowns. Style AA high-impact and abrasion-resistant nylon buckets and ductile iron “digger” buckets were used to provide a very robust design.