Overview
EN ISO 4263-2:2003 - Petroleum and related products: Determination of the ageing behaviour of inhibited oils and fluids - TOST test, Part 2: Procedure for category HFC hydraulic fluids - is a CEN-endorsed ISO method for accelerated ageing of HFC (water‑glycol) hydraulic fluids. The standard defines a laboratory procedure that accelerates degradation by exposing samples to oxygen, water and metal catalysts at elevated temperature and monitors the fluid’s deterioration by pH and insolubles content.
Key topics and requirements
- Scope: Applies to HFC hydraulic fluids as defined in ISO 6743-4 and specified in ISO 12922.
- Principle: Test portions are reacted (in the dark) at 95 °C with oxygen and a steel/copper catalyst coil; small aliquots are withdrawn periodically to measure pH and insolubles.
- End points: Test ends when pH reaches 4.0, insolubles exceed 4.0 % (m/m), or 200 h elapses.
- Reagents & materials: Grade‑2 laboratory water, heptane (≥99.75 %), acetone, propan‑2‑ol, oxygen (≥99.5 %) and defined catalyst wires (steel ~1.60 mm, copper ~1.63 mm).
- Apparatus: Borosilicate oxidation cell (300 ml mark), thermostatically controlled heating bath maintaining 95 °C ±0.2 °C, flowmeter (≥3 l/h, ±0.1 l/h), and temperature measurement to ±0.1 °C.
- Safety & quality: The standard warns of hazardous materials (oxygen service, hot equipment) and references cleaning, sampling and calibration practices.
- Measurement methods: Includes normative annexes for thermometer specifications, catalyst coil handling, and a method to determine insolubles content.
Applications and users
EN ISO 4263-2:2003 is used for:
- Hydraulic fluid manufacturers - formulation development and stability screening of HFC fluids.
- Independent test laboratories - routine ageing tests, comparative evaluation and certification testing.
- OEMs and end‑users (industrial/hydraulic systems) - fluid selection, supplier qualification and maintenance planning.
- Quality assurance and R&D teams - shelf‑life assessment, additive performance and failure‑mode analysis.
Practical outcomes include accelerated prediction of service life, additive efficacy evaluation, and support for specifications for fire‑resistant hydraulic fluids.
Related standards
- ISO 4263 (other parts): Part 1 (mineral oils), Part 3 (anhydrous synthetics), Part 4 (industrial gear oils)
- ISO 6743-4 (fluid classification), ISO 12922 (HFC specification)
- ISO 20843 (pH determination of fire-resistant fluids), ISO 3170 (manual sampling), ISO 3696 (water for laboratory use)
Keywords: EN ISO 4263-2:2003, TOST test, HFC hydraulic fluids, ageing behaviour, hydraulic fluids testing, pH, insolubles content, accelerated ageing, ISO 4263-2.
