ISO 20844:2015

Overview

ISO 20844:2015 specifies a standardized laboratory method to determine the shear stability of polymer-containing mineral, synthetic and related oils by passing the fluid through a specified diesel injector nozzle. Shear stability is reported as the percentage change in kinematic viscosity (typically measured at 40 °C and at 100 °C as required) caused by polymer degradation under controlled mechanical shear. The method provides repeatable, minimized thermal/oxidative test conditions for ranking formulations rather than predicting in-service performance.

Key Topics and Requirements

• Test principle: Pump a test portion through a diesel injector nozzle at high pressure for a defined number of passes; measure viscosity before and after to calculate shear-induced viscosity loss.
• Test rig and environment: A purpose-built rig (Annex A) with regulated cooling water, ambient 20–25 °C and reservoir fluid maintained ~30–35 °C.
• Nozzle setup: Injector opening pressure adjustment (static or dynamic). Dynamic opening pressure range specified: 13.0 MPa to 18.0 MPa.
• Flow and volume controls: Flow rate typically 170 ml·min⁻¹ ± 5 ml·min⁻¹; dead volume between stopcock and nozzle outlet 20 ml ± 0.5 ml; minimum sample volume 600 ml.
• Referencing and calibration: Regular referencing using CEC Reference Fluid RL 233 (30-cycle reference) to derive a correction factor (F). Nominal shear loss for the reference fluid after 30 cycles: 2.80 mm²/s (used to calculate F). Reference runs required at intervals ≤ 500 cycles or after maintenance.
• Viscosity measurement: Conform to ISO 3104 for kinematic viscosity measurement (baths at 40 °C and 100 °C as needed).
• Safety note: Standard warns of hazardous materials/operations and delegates responsibility for safe practices to the user.

Applications and Users

• Fluid and additive manufacturers use ISO 20844:2015 to rank and screen polymer-thickened oils and additive packages for resistance to mechanical shear.
• Hydraulic fluid formulators (categories HR and HV per ISO 6743‑4 and ISO 11158) employ the method to assess viscosity retention under shear.
• Specialty fluids: The method can be adapted (with modified conditions as per ISO 12922) for certain fire‑resistant hydraulic fluids (HFA, HFB, HFC, HFD).
• Quality control and R&D labs** performing comparative testing and formulation optimization.
• Note: The standard provides standardized ranking conditions; it does not establish a direct correlation with field performance.

Related Standards

• ISO 3104 - kinematic viscosity measurement
• ISO 3170 - sampling of petroleum liquids
• ISO 4113 - calibration fluids for diesel injection equipment
• ISO 6743‑4, ISO 11158 - hydraulic fluid categories and specifications
• ISO 12922 - modifications for fire‑resistant fluids
• CEC Test Method L‑14‑93 - referenced alignment and history

Keywords: ISO 20844:2015, shear stability, polymer-containing oils, diesel injector nozzle, viscosity loss, hydraulic fluids, CEC Reference Fluid RL 233, test rig, ISO 3104.