ISO 10050:2005

Overview

ISO 10050:2005 specifies the required characteristics of unused triaryl phosphate ester turbine control fluids (category ISO‑L‑TCD) used in turbine governor controls and other hydraulic systems in electrical power stations. The standard covers composition, sampling, test methods and performance limits for fluids intended for turbine control applications. It emphasizes fire‑resistant properties, hydrolytic and oxidation stability, and compatibility with elastomers and hydraulic components.

Key topics and technical requirements

• Composition: Fluids are organic phosphate esters with aryl or substituted aryl groups; commercial formulations may include stabilizers and antifoam additives. Use of viscosity index improvers is not allowed. Dyes for identification are permitted.
• Viscosity grades: Specified to ISO 3448; common grades covered include ISO VG 32 and 46 with kinematic viscosity limits at 40 °C and maximum low‑temperature viscosities.
• Physical and chemical limits (examples from Table 1):
  • Density at 15 °C: max 1 200 kg/m3
  • Neutralization number (total acid number): max 0.1 mg KOH/g
  • Water content: max 1.0 g/kg
  • Pour point: max −15 °C
  • Manifold ignition test: minimum 700 °C; fire point: minimum 300 °C
• Performance tests and stability: Oxidation stability and corrosivity, hydrolytic stability (EN 14832 / EN 14833), foaming behavior (ISO 6247), air‑release (ISO 9120) and water separability (ISO 6614).
• Contamination and cleanliness: Particle cleanliness coded to ISO 4406; recommended particle counting methods include ISO 11500 and ISO 11171 calibration.
• Electrical and additive limits: Direct current resistivity (IEC 60247) and maximum chlorine content (ISO 15597).
• Sampling and test methods: Sampling per ISO 3170 and many referenced test standards (ISO 3104, ISO 760, ISO 2592, etc.).
• Safety note: Fluids are difficult to ignite but not non‑flammable; handling and maintenance precautions (see IEC 60978) are mandatory.

Applications

• Specification and acceptance of turbine control fluids for hydraulic governor systems in thermal, hydro and nuclear power stations.
• Procurement and quality control of fire‑resistant turbine fluids.
• Laboratory testing and type‑approval of fluids for compatibility with seals, elastomers and hydraulic components.
• Guidance for maintenance regimes, contamination control and safety procedures in power plant hydraulic systems.

Who uses this standard

• Power plant engineers and maintenance teams
• Lubricant and hydraulic fluid manufacturers
• Procurement and quality assurance professionals
• Test laboratories and certification bodies
• OEMs of turbine governors and hydraulic control equipment

Related standards

• ISO 6743‑5 (family T classification), IEC 60978 (maintenance/use guide), EN 14832 / EN 14833 (stability tests), ISO 3104, ISO 760, ISO 4406, IEC 60247.

Keywords: ISO 10050:2005, triaryl phosphate ester, turbine control fluids, ISO‑L‑TCD, turbine governor controls, fire‑resistant hydraulic fluids.