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Best Practices in Wood Waste Recycling Click here for printable PDF version
Use of Rolling Stock to Sort, Pre-Process, Material: Wood Waste Issue: Depending on the
raw material sourcing strategy of a processing facility,
wood waste such as lumber trim, land clearing debris,
commingled demolition, pallets, typically vary in type
and dimension. These
variations in raw materials require a flexible, multi-purpose
mechanism for handling incoming material at the facility.
The equipment needs to be able to sort incoming wood
waste into appropriate storage areas according to quality
and type and to effectively convey wood materials ranging
from sawdust to large wooden containers.
In some cases, it may be necessary to pre-process
the wood waste to accommodate the processing in-feed
system or other equipment. Best
Practice:
This Best Practice recommends using multi-purpose
rolling stock (typically front-end loaders and excavators)
coming into a wood-waste processing facility to serve
critical functions:
following are the Rolling
Stock Functions: Rough Sorting and Separation. The rolling stock is typically the first equipment to interact with delivered wood waste and introduces the material into the processing system. As each truckload of wood waste is dumped in the receiving yard, the rolling stock operator categorizes the type of material and conveys the wood to the appropriate segregated storage area. These storage areas may be divided storage bunkers or isolated piles. In some instances, it may be possible for the rolling stock operator to roughly sort out different types of wood waste from a single delivered load. Pre-Processing Wood Waste. Wood waste is sometimes delivered to a plant in shapes or sizes that are incompatible with the processing equipment. For example, large wood containers or tree stumps may be too bulky to load into the in-feed system of the size-reduction equipment. Rolling stock and its attachments can effectively crush, compact, cut, and shear bulky wood waste prior to loading into the processing system. (Equip rolling stock with solid- or foam-filled tires so that the prevalent metal contaminants in the wood waste do not cause excessive maintenance problems). Moving Raw Wood Waste to In-feed Systems. Rolling stock is widely used to convey wood waste from segregated
storage areas to the processing infeed system.
While loading wood waste into the system at a
steady rate, the rolling stock is generally capable
of orienting the material so that it is favorably presented
to the conveyors and size-reduction equipment. Types of Rolling Stock. Rolling stock used at wood-waste processing facilities comes in many different styles and sizes, the most common of which are front-end loaders and excavators. The front-end loader is a movable piece of equipment, whereas the excavator is generally a stationary set-up where work activities can be performed within the reach of its boom. As a result, the front-end loader is best suited to moving material from place-to-place and an excavator with a grapple is best suited for loading material into an in-feed system from a nearby pile. In general, a front-end loader can perform the full range of rolling stock functions and handle diverse types and sizes of wood waste. Rolling stock operates most effectively on flat, concrete surfaces. Concrete or steel back-up walls behind stored wood piles also improve rolling stock operation. Types of Attachments. Front-end loaders and excavators can be fitted with customized and removable attachments to efficiently perform specific functions. The appropriate attachment for a facility depends on the type of wood waste it accepts. For example, it may be appropriate for processing facilities that handle relatively large volumes of landclearing debris, whole trees, and other green waste to be equipped with a front-end loader equipped with clamping mill-yard forks. Types of rolling stock attachments that might be used at a wood waste processing facility:
Wheeled Vs. Tracked Rolling Stock. Rolling stock equipment can run on either wheels or tracks. Both have advantages and disadvantages. In general, operators find that wheeled loaders with solid tires work well in most processing situations. However, they are limited in their ability to push large volumes of material around without slipping giving tracked loaders an advantage for stockpiling. Tracked equipment is generally best suited to the lower value wood waste products and more limited functions. However, in the course of bulk reduction, tracked loaders tend to crush the wood waste too much and create a lot of fines (very small particles). Implementation: Rolling stock is readily available from new and used equipment vendors, because rolling stock is very costly and has high maintenance costs, equipment should be selected with care. Selection Considerations.
The primary issues that an operator should consider
in the selection of rolling stock equipment are:
operational issues (effectiveness, compatibility
with process equipment, capability to handle targeted
production throughput, etc.), capital cost, maintenance,
and safety issues.
With an equipment vendor, rolling stock can be
carefully sized to handle the types and sizes of wood
waste processed at a given facility and to handle the
tonnage processing capacity of that facility.
Operator training is also key to effective and
safe rolling stock utilization. Benefits: Effective use of rolling stock at the front-end of a wood waste processing facility will accomplish a number of important processing functions including:
Optimally,
using such equipment maintains maximum and continuous
throughput capacity of the processing line.
In addition, rolling stock equipment should be
flexible and multi-purpose in supporting many other
functions in the plant. Application Site: This Best Practice applies to wood-waste processing facilities. Contact: For more information about this Best Practice, contact CWC (206) 443-7746, e-mail info@cwc.org. References: 1. International Resources Unlimited, Inc.; Eugene, OR. 2. “Investigation of Alternative Markets for Recycled Wood,” prepared by International Resources Unlimited, Inc. for the Portland Metropolitan Service District; 1992. 3. Walsh , Dan; Northwest Wood and Fiber Recovery; Portland, OR. 4. Sargent , Bob; Rainier Wood Recycling; Seattle, WA. (See Appendix for an Equipment Manufacturer’s List.) Issue Date / Update: March 1997
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