Contact OREGON® for answers to your
technical and product questions.
Mechanical-Harvester (chain, bars,
sprockets and accessories):
What is chain shot?
Chain shot is the high velocity separation and ejection of a piece or pieces of cutting chain from the end of a broken chain in mechanized timber harvesting. Chain shot exposes both machine operators and bystanders to a risk of serious injury or death. Chain shot typically occurs near the drive end of the cutting system but can also come from the bar tip area.
Industry research indicates an average of 1 in 50 broken chains had parts missing that may have been the result of a chain shot event.
How can operators reduce the risk of chain shot?
- Operators and bystanders must never be in the plane of the bar when the chain is in motion on the bar.
- Appropriate windshield material must be installed.
- Chain speed must be 40 m/s (8000 ft/min) or less for .404 pitch Oregon® Harvester chain and 35 m/s (7000 ft/min) or less for 3/4 pitch Oregon® Harvester chain.
- A chain shot guard should be installed near the drive sprocket.
- Bystanders must be at least 70 meters (230 ft.) away from the harvester.
- Chains should be inspected frequently and damaged or cracked chains removed from service.
- Always use new Oregon® parts when repairing Oregon® chains.
- Industry groups recommend that chains should be discarded after the second break.
- Remove all dull and/or worn chains from service.
- Always sharpen Oregon® chains to Oregon® factory specifications.
- Maintain proper bar and chain lubrication.
- Maintain proper chain tension.
- Replace the drive sprocket when it has visible signs of wear.
For additional information see the Oregon® Mechanical Timber Harvesting Handbook.
How does chain shot occur?
A chain shot consists of two breaks in a chain as demonstrated in the computer simulation. First, the loop of chain breaks and forms two ends. One end moves past the drive sprocket or bar nose and is rapidly accelerated due to a whip-like motion of the chain end. The "whip action" causes the second break releasing small parts at super sonic speed.
Chain shot can cause chain parts to be thrown in
many directions, especially those along the plane of the saw bar.
What does a typical chain shot piece look like?
The most dangerous chain shot parts consist of one to four parts as shown:
Can chain shot and related injuries be eliminated from mechanized timber harvesting and processing?
No!! Operators must always treat an operating chain and bar with the potential danger of a loaded rifle. The following are just a few examples why chain shot can not be eliminated.