ISO 11365:2025

Overview

ISO 11365:2025 - "Petroleum and related products - Maintenance and use of triaryl phosphate ester turbine control fluids - Guidance and requirements" provides consolidated guidance and mandatory requirements for the safe use, maintenance, testing and storage of triaryl phosphate ester fire‑resistant turbine control fluids. This second edition replaces ISO 11365:2017, clarifies scope (explicitly covering HFDR fluids in ISO 6743‑4 and TCD/TSD/TGD in ISO 6743‑5) and adds supplementary fluid monitoring procedures.

Key topics and technical requirements

The standard covers practical and technical topics essential to maintaining fluid performance and system safety:

• Scope and definitions specific to triaryl phosphate ester fluids and relevant HFDR/TCD/TSD/TGD categories.
• Health, safety and waste disposal: handling precautions, PPE and end‑of‑life considerations.
• Fire hazards and extinguishing: fire behaviour and recommended extinguishing approaches for phosphate ester fluids.
• Material compatibility: seals, paints, gaskets and electrical cable insulation compatibility guidance.
• Factors affecting service life: system design, operating conditions, maintenance and contamination sources (air, water, particulates, mineral oil, metal soaps, chlorinated materials).
• Fluid condition monitoring and purification: recommended monitoring frequency and purification/top‑up practices.
• Delivery, storage and flushing: acceptance of new deliveries, storage best practices and system flushing procedures.
• Sampling and laboratory testing: sampling points, containers, labelling and test methods.
• Recommended monitoring tests (examples listed in the standard): appearance and colour, water content, neutralization (acid) number, cleanliness, resistivity, chlorine and mineral oil content, viscosity, air release, foaming, membrane patch colorimetry, metals, linear sweep voltammetry and manifold ignition temperature.
• Acceptance and trend analysis: acceptance tests for new fluid charges and ongoing evaluation of used fluid for life‑cycle decisions.

Practical applications and users

ISO 11365:2025 is intended for organizations that manage turbine and power‑generation hydraulic systems where triaryl phosphate ester fluids are used. Typical users include:

• Power plant operators and maintenance teams
• Turbine manufacturers and OEMs
• Hydraulic system designers and reliability engineers
• Lubricant analysts and laboratory personnel
• Health, safety and environmental (HSE) managers
• Procurement and storage facility managers

Use cases: establishing maintenance programs, specification of acceptance tests for new fluid deliveries, designing sampling and monitoring plans, selecting compatible system materials, and defining safe handling and disposal procedures.

Related standards

• ISO 6743‑4 (lubricant classifications - HFDR category)
• ISO 6743‑5 (lubricant classifications - TCD, TSD, TGD categories)
• ISO 11365:2017 (previous edition - canceled and replaced)

Keywords: ISO 11365:2025, triaryl phosphate ester, turbine control fluids, fire‑resistant fluids, hydraulic systems, fluid monitoring, power generation maintenance.