Harvester Chain Shot:
Harvester/Processor/Slasher/Delimber Chain Shot:
Welcome to the Mechanized Timber Cutting Equipment Chain Shot information page. The following information is for professional users and manufacturers of mechanized timber cutting equipment using saw chain based cutting systems.
The following are some recommendations for protecting yourself from injury while taking advantage of the tremendous utility and labor savings afforded by Mechanized Timber Cutting Equipment.
A Mechanized Timber Harvester/Processor/Slasher/Delimber puts enormous stress on saw, creating the need to follow instructions that minimize the risk of chain breakage and the potential for injury. Be absolutely sure to thoroughly read and understand the operator's manual supplied with your equipment. Follow exactly the manufacturer's safety and maintenance instructions. The following information is meant to supplement, not replace, the information provided in the operator's manual for your specific equipment.
Chain shot is an important industry topic that is currently being studied. A lot is known about the cause, effects, and ways to minimize injuries from chain shot. But, there is still more to learn. Please check back to this site for updates on chain shot.
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 ?
1. Operators and bystanders must never be in the plane of the bar when the chain is in motion on the bar.
2. Appropriate windshield material must be installed.
3. 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.
4. A chain shot guard should be installed near the drive sprocket.
5. Bystanders must be at least 70 meters (230 ft.) away from the harvester.
6. Chains should be inspected frequently and damaged or cracked chains removed from service.
7. Always use new OREGON® parts when repairing OREGON® chains.
8. Industry groups recommend that chains should be discarded after the second break.
9. Remove all dull and/or worn chains from service.
10. Always sharpen OREGON® chains to OREGON® factory specifications.
11. Maintain proper bar and chain lubrication.
12. Maintain proper chain tension.
13. Replace the drive sprocket when it has visible signs of wear.
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.