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ISO 28139:2019 — Equipment for Crop Protection — Knapsack Engine-Driven Airblast Sprayers
Technical Article
1. Scope and Importance of ISO 28139:2019
ISO 28139:2019 specifies safety and environmental requirements and test methods for knapsack combustion engine-driven airblast sprayers used in crop protection. These portable machines are widely used in agriculture and forestry for applying pesticides, herbicides, and fertilizers in terrains inaccessible to vehicle-mounted sprayers, such as steep slopes, dense plantations, and smallholder farms in developing regions. This second edition supersedes both ISO 28139:2009 and ISO 10988:2011, adding comprehensive environmental requirements including droplet size control to minimize drift, residual liquid limits, and updated safety provisions reflecting current technology. The standard was prepared by ISO/TC 23 Tractors and machinery for agriculture and forestry, Subcommittee SC 6 Equipment for crop protection.
The standard covers the complete product lifecycle: design specifications, construction requirements, performance testing, and information for use including instruction handbooks and warnings. It addresses all significant hazards associated with these machines as identified in Annex A, including mechanical, thermal, vibration, noise, and chemical hazards. The standard has been updated to reflect the latest understanding of operator safety and environmental protection in crop protection applications.
This second edition supersedes both ISO 28139:2009 and ISO 10988:2011, adding comprehensive environmental requirements and updating the standard to reflect the current state of the art in sprayer technology.
2. Key Safety Requirements for Operator Protection
The standard addresses numerous safety aspects critical for protecting operators during sprayer operation in demanding field conditions, covering mechanical, thermal, vibration, noise, electrical, and chemical hazards:
| Safety Requirement | Specification | Verification Method |
|---|---|---|
| Stability during operation | Must maintain stability on defined slopes without tipping | Stability test per Annex C |
| Exhaust system | Properly positioned to prevent burns and operator exposure to exhaust gases | Temperature measurement and positioning inspection |
| Controls | Throttle trigger, engine stopping device, liquid shut-off valve all clearly marked and accessible | Functional testing |
| Harness system | Adequate load distribution with absorbent carrying straps | Visual inspection plus absorbency test |
| Hot parts protection | Guards fitted to prevent accidental contact with hot surfaces | Temperature measurement of accessible surfaces |
| Vibration | Reduction by design at source, measured per ISO 20643 | Accelerometer measurement at handles |
| Noise | Sound power level limits, reduction by design | Sound level meter per ISO 3744 |
| Electromagnetic immunity | Must operate correctly in typical agricultural EM environments | Immunity testing per relevant standards |
Operator safety is paramount: the standard mandates that ignition circuit components must be adequately insulated and that the engine stopping device must be clearly identifiable and easily accessible, with the stop function clearly marked. The vibration measurement must account for both handles.
3. Environmental Requirements and Test Methods
A major addition in this edition is the comprehensive set of environmental requirements aimed at reducing ecological impact. Droplet size control is critical: the sprayer must produce appropriately sized droplets to minimize off-target drift while maintaining effective crop coverage. Spray tank specifications include strainers and filters to prevent nozzle clogging, a contents gauge for liquid level indication, and limits on total residual liquid after emptying to minimize chemical waste. The fan must provide sufficient air velocity for proper droplet transport, measured using a defined sampling grid per Annex B. The carrying strap material must not absorb excessive pesticides, reducing operator exposure during extended use. Chemical hoses must withstand operating pressures without leakage.
| Environmental Parameter | Requirement | Purpose |
|---|---|---|
| Droplet size distribution | Controlled to minimize drift | Reduce environmental contamination |
| Carrying strap absorbency | Must not absorb excessive pesticide liquid | Reduce operator dermal exposure |
| Spray tank material | Resistant to agrochemical attack | Prevent leaks, ensure durability |
| Total residual liquid | Minimized after emptying | Reduce chemical waste disposal |
| Chemical hoses | Pressure-rated, leak-proof connections | Prevent operator contact |
Droplet Size Classification
The standard references established droplet size classification categories used in crop protection. Proper droplet size selection depends on the target crop, pesticide type, and environmental conditions. The classification system helps operators choose appropriate nozzles and operating parameters:
| Category | VMD Range (micrometers) | Typical Application |
|---|---|---|
| Very Fine (VF) | < 100 | Fungicides, insecticides requiring thorough coverage |
| Fine (F) | 100 – 175 | Contact herbicides, thorough canopy penetration |
| Medium (M) | 175 – 250 | Systemic herbicides, broadleaf weed control |
| Coarse (C) | 250 – 375 | Pre-emergence herbicides, drift-sensitive areas |
| Very Coarse (VC) | > 375 | Soil-applied herbicides, maximum drift reduction |
The fan speed, liquid pressure, and nozzle type all influence the resulting droplet size distribution. Manufacturers must provide clear guidance on achievable droplet size ranges for their equipment under various operating conditions, enabling operators to make informed choices for each application scenario.
Engineering Design Insights
For manufacturers, achieving ISO 28139 compliance requires a holistic engineering approach. The stringent vibration requirements demand carefully designed engine mounting systems with appropriate isolation. The exhaust system must balance noise reduction against backpressure constraints that affect engine performance. The harness system requires both extended-wear comfort and resistance to pesticide absorption, typically achieved through multi-layer fabric construction with chemical-resistant coatings. The liquid handling system needs leak-proof connections throughout, with chemically resistant materials such as polypropylene or stainless steel for wetted components. Modern designs increasingly incorporate electronic engine management for consistent performance and lower emissions. The fan system design is particularly critical: it must generate sufficient air velocity for adequate droplet transport while minimizing energy consumption and maintaining acceptable noise levels. Computational fluid dynamics (CFD) simulation is increasingly used during development to optimize the air duct geometry and nozzle placement for uniform spray distribution patterns.
The inclusion of comprehensive environmental requirements in this standard represents the industry’s commitment to reducing pesticide drift and environmental contamination while maintaining effective crop protection capabilities.
4. FAQs
Q: What types of sprayers are covered by ISO 28139?
A: It covers knapsack combustion engine-driven airblast sprayers only. Electric or battery-powered sprayers are not within scope and may be covered by other standards.
A: It covers knapsack combustion engine-driven airblast sprayers only. Electric or battery-powered sprayers are not within scope and may be covered by other standards.
Q: How is droplet size measured for compliance?
A: Droplet size is determined through standardized test methods using laser diffraction or other suitable measurement techniques as specified in the environmental test provisions.
A: Droplet size is determined through standardized test methods using laser diffraction or other suitable measurement techniques as specified in the environmental test provisions.
Q: What information must the instruction handbook contain?
A: Technical data including engine power, tank capacity, weight, noise and vibration values; operating instructions; maintenance schedules; safety precautions; and environmental protection guidance.
A: Technical data including engine power, tank capacity, weight, noise and vibration values; operating instructions; maintenance schedules; safety precautions; and environmental protection guidance.
Q: What are the main changes from the 2009 edition to the 2019 edition?
A: The 2019 edition adds environmental requirements and tests, updates safety requirements to current technology, and excludes ergonomics which is now covered by separate standards.
A: The 2019 edition adds environmental requirements and tests, updates safety requirements to current technology, and excludes ergonomics which is now covered by separate standards.