ISO 11839:2021

Overview

ISO 11839:2021 - Machinery for forestry - Thrown object guard - Test method and performance criteria - defines a laboratory test method and performance requirements for thrown object guards (TOG) intended to protect operators of mobile and self‑propelled forestry machinery from cutting or grinding elements and residual matter thrown by attachments. The standard applies to TOGs incorporated into operator protective structures (ROPS/FOPS/OPS) or provided as independent guards. Tests are specific to each cutting or grinding attachment and host machine model and do not cover saw chain shot (see ISO 21876).

Key Topics

• Scope and purpose: Establishes repeatable laboratory procedures and pass/fail performance criteria for TOG effectiveness against projectiles generated by powered cutting or grinding attachments.
• Risk assessment: Requires a prior risk assessment (ISO 12100) to identify panels in the operator’s path and to determine worst‑case mass and tip velocity for the cutting/grinding element.
• Impact objects (F1, F2, F3):
  • F1 / F2 profiles: Representative sawtooth profiles for circular disc saws (shankless and shank types).
  • F3 profile: Spherical impact object with mass selected from defined ranges (actual or standardized masses: <250 g = actual mass; 250–399 g = 325 g; 400–599 g = 500 g; 600–999 g = 800 g; 1 000–1 599 g = 1 300 g; 1 600–2 600 g = 2 100 g; >2 600 g = actual mass).
• Instrumentation & accuracy:
  • Mass scale accuracy ±1% of impact object mass.
  • Velocity measurement accuracy ±2 m/s.
  • Materials per ASTM A‑108 (or equivalent) for impact objects.
• Launcher & test setup: Controlled impact object launcher (sabot permitted) that sets orientation, direction and velocity; test velocity derived from kinetic energy equivalence calculations:
  • KE = 1/2 m0 v0^2
  • vt = sqrt(2·KE / mt)
  • vp = (cos θ) · vt
• Safety: Dynamic projectile testing demands containment structures and laboratory risk controls.

Applications

• Manufacturers and designers of forestry machinery and thrown object guards (TOG) use ISO 11839:2021 to:
  • Validate TOG designs for specific cutting/grinding attachments and host machines.
  • Inform selection of panel materials, mounting hardware and integration with ROPS/FOPS/OPS.
• Independent testing laboratories implement the laboratory test method and reporting requirements.
• Safety engineers, conformity assessors and procurement teams use the standard for specification, compliance and performance verification.

Related standards

• ISO 12100 - Risk assessment and risk reduction
• ISO 6814 - (related forestry machinery definitions)
• ISO 21876 - Saw chain shot hazards (separate standard)
• ISO 898‑1 / ISO 898‑2 - Fastener mechanical properties
• ISO 9248, ISO 3411, ASTM A‑108 - referenced test/measurement and material standards

Keywords: ISO 11839:2021, thrown object guard, TOG, forestry machinery, test method, performance criteria, impact object, kinetic energy, operator protection.