ISO 6743-12:1989 PDF

Overview

ISO 6743-12:1989 specifies the classification of heat transfer fluids within the broader ISO 6743 family for lubricants, industrial oils and related products (class L). It defines product categories (Family Q) and a uniform designation system for fluids used in heat transfer applications. The standard is intended to be read together with ISO 6743-0 (general rules) and uses viscosity grades defined in ISO 3448.

Key topics and requirements

• Category coding: Each product is given a two‑letter code starting with “Q” (e.g., QA, QB). The second letter identifies the specific category; the pair forms a standard code for the fluid family.
• Temperature- and system-based categories: Categories in the detailed classification address typical operating conditions and system types:
  • Q A - Open-circuit heat transfer fluids; bulk temperature up to <250 °C; fire risk and open container considerations.
  • Q B - Closed-circuit fluids for general heat transfer; bulk temperature up to <300 °C.
  • Q C - Closed-circuit fluids with forced circulation for higher temperatures >300 °C and <320 °C; systems require filtration and circulation.
  • Q D - Synthetic fluids for particularly high temperatures (bulk measured with forced circulation >320 °C).
  • Q E - Cooling circuits where fluid must perform at low temperatures **> −30 °C and