ISO 789-9:2018

Overview

ISO 789-9:2018 - "Agricultural tractors - Test procedures - Part 9: Power tests for drawbar" specifies standardized test procedures to determine the power available at the drawbar of agricultural tractors of wheeled, track‑laying or semi‑track‑laying types. This second edition (2018) harmonizes with OECD Code 2 (2017) and defines methods, measurement units, tolerances and reporting requirements for drawbar power and associated fuel‑use measurements.

Key Topics and Requirements

• Scope and selection: Tests apply to production tractors; manufacturer and test body collaborate on tractor selection. A manufacturer’s representative is required during testing.
• Measurement units & tolerances: Specified accuracies for rotational speed (±0.5 %), force (±1 %), fuel consumption (±1 %), temperatures and other key quantities.
• Pre-test conditions: New, run‑in tractors per manufacturer instructions; adjustments allowed before testing but not during.
• Fuels & lubricants: Use commercially available products conforming to manufacturer or national/international standards. Fuel consumption measurement during drawbar tests is mandatory.
• Diesel particulate filters: Regeneration may be performed before testing; tests are paused if regeneration begins during a run.
• Auxiliary equipment: Accessories may only be disconnected if allowed by the operator’s manual; variable parasitic loads must be accounted for in reports.
• Ambient & tractor conditions: No atmospheric corrections are made; atmospheric pressure should not be less than 96.6 kPa and ambient temperature around 20 °C ± 15 °C. Tyre or track tread height must be at least 65% of new as measured per Annex A.
• Slip measurement: Wheel/track slip is defined and measured as part of drawbar testing; procedures for maximum power, fuel consumption at nominal speeds, and continuous tests are provided.
• Reporting: A standardized test report is required (see ISO 789‑13 vocabulary and specimen report).

Applications and Users

ISO 789-9 is used by:

• Tractor manufacturers for performance verification and R&D
• Third‑party test laboratories and certification bodies conducting conformity or comparative testing
• Agricultural equipment designers and implement manufacturers checking compatibility with drawbar power ratings
• Research institutions analyzing tractor performance and fuel efficiency

Practical uses include establishing performance claims, comparing models, validating transmission and traction systems, and supporting product documentation.

Related Standards

• ISO 789 series (other parts cover related tractor tests)
• ISO 789-13:2018 - Vocabulary and specimen test report (normative reference)
• Harmonized with OECD Code 2: 2017

Keywords: ISO 789-9, drawbar power, agricultural tractors, drawbar tests, test procedures, fuel consumption, tyre slip, test report.