ISO 12925-1:2024

Overview

ISO 12925-1:2024 specifies requirements for lubricants, industrial oils and related products (Class L), Family C (gears) specifically intended for enclosed gear systems. This third edition updates performance and environmental criteria for gear oils used across industries - from machine tools to heavy mining and cement plant gearboxes. It applies only to enclosed gears; open-gear lubricants and greases are covered in other parts of the ISO 12925 series.

Key technical topics and requirements

• Scope and categories: Covers the Family C categories defined in ISO 6743-6 including CKB, CKC, CKD, CKE, CKSMP, CKTG, CKES, CKPG, CKPR, CSPG, CSPR, CTPG and CTPR.
• Environmental requirements: For categories CKTG, CKES, CKPG and CKPR the standard defines minimum base-fluid composition (category‑defining base fluid ≥ 50% and total base fluid mass fraction ≥ 70% per Table 1) and environmental performance criteria. Biodegradability (min. 60% mineralization in 28 days) and aquatic toxicity limits are specified (see Table 2).
• Performance characteristics: Specifies tests and limits for ageing (TOST), scuffing and scuff-resistance (FZG), micro-pitting resistance (added protection level for CKSMP), foaming, air release and water separability. Precision and sampling rules reference ISO 3170 and other normative methods.
• Test methods referenced: Includes widely used standards such as ISO 14635-1 (FZG), ISO 4263-4 (TOST for gear oils), ISO 6247 (foaming), ISO 12152 (spur gear foam/air-release test), ISO 14593 / ISO 9439 (biodegradability) and toxicity standards for daphnia, copepods and fish.
• Limitations: Not intended for extreme or exceptional gear designs and service conditions; manufacturers and users may agree on additional tests where needed.

Practical applications

• Specifying and procuring gear oils for enclosed gearboxes in industries such as steel mills, cement plants, mining, and machine tools.
• Guiding product development for lubricant manufacturers to meet performance and environmental targets (micro-pitting control, foam/air-release, ageing resistance).
• Setting acceptance criteria for condition monitoring, lubricant replacement and OEM gearbox specifications.
• Assisting compliance teams in selecting environmentally acceptable gear oils (vegetable triglycerides, esters, polyglycols, PAOs) that meet biodegradability and toxicity baselines.

Who should use ISO 12925-1:2024

• Lubricant and additive manufacturers
• Gearbox/OEM designers and maintenance engineers
• Procurement and specification writers
• Testing laboratories and certification bodies
• Environmental compliance officers evaluating bio-based gear oils

Related standards (read in conjunction)

• ISO 6743-6 (family classification)
• ISO/TR 18792 (gear and lubricant selection guidance)
• ISO 14635-1, ISO 4263-4, ISO 12152, ISO 6247, ISO 14593 / ISO 9439 (test methods)
• EN 16807 (bio-lubricant criteria)

Keywords: ISO 12925-1:2024, gear oils, lubricants for enclosed gear systems, industrial oils, environmental requirements, biodegradability, ISO 6743-6.