Overview
ISO 11837:2011 specifies a standardized test method and performance criteria for saw chain shot guarding systems used on harvester heads and grip saws of forestry machines. The standard addresses protection against saw chain breakage on the cutting side of the guide bar and defines the test apparatus, procedures, pass/fail criteria and reporting requirements to evaluate a guarding system’s ability to prevent high‑speed flying chain fragments (saw chain shot).
Key Topics and Requirements
- Scope: Applies only to saw chain breakage on the cutting side of the guide bar; alternative test methods may be used if shown equivalent.
- Test apparatus: Attach the guarding system (or complete harvester head/grip saw) to a rig that simulates real mounting and obstacles that might influence chain behavior.
- Drive and speed control: Saw chain speed adjustable between 30 m/s and 60 m/s with a tolerance of ±2 m/s; drive shaft speed measurement uncertainty ±1%.
- Pre‑calibration: Ten calibration runs without guarding - five at 0.8C and five at 1.2C (C = maximum design saw chain speed). At least four of five runs at each speed must produce chain shots on reference panels.
- Reference panels: Two panels (approx. 400 mm × 1 000 mm) placed per the standard to detect chain penetration.
- Saw chain, guide bar and sprocket selection: Use manufacturer‑recommended chain and the longest available guide bar; preferred chain sizes are listed (e.g., 0.404" pitch, 1.6 mm or 2.0 mm thickness; 3/4" pitch, 3.1 mm thickness).
- Saw chain stopping device: Positioned relative to guide bar length (positions at approximately 0.5X and 0.8X, where X is distance from sprocket centre to guide bar tip).
- Protective cover: Test enclosure strength at least equivalent to 6 mm steel sheet; tests produce hazardous chain shots and must only be performed with cover in place.
- Performance criteria: Any penetration of a reference panel during a test run = failure. Wear allowance after 24 endurance runs: maximum 50% of original thickness or 2 mm, whichever is less.
- Reporting: Test report must include rig description, test results, chain photographs, and reference to ISO 11837.
Applications and Who Uses It
- Manufacturers of harvester heads, grip saws and guarding systems - for product development and conformity testing.
- Independent test laboratories - to certify guarding performance and produce comparable test data.
- Safety engineers, forestry operators and procurement teams - to select equipment with validated protection against chain shot.
- Regulators and standards bodies - as a technical reference for machine safety requirements.
Related Standards
- Prepared by ISO/TC 23 (Tractors and machinery for agriculture and forestry). Use in conjunction with manufacturer instructions and applicable national machine safety regulations. Other test methods may be accepted if proven equivalent.
Keywords: ISO 11837:2011, saw chain shot, saw chain shot guarding systems, test method, performance criteria, harvester heads, grip saws, forestry machinery.
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