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D6080-18 – Standard Test Method Technical Guide
📐 Scope and Applicability
This practice covers all hydraulic fluids based on petroleum, synthetic, or naturally-occurring base stocks. It is not intended for water-containing hydraulic fluids. The practice is applicable to fluids with a kinematic viscosity ranging from approximately 4 mm²/s to 150 mm²/s at a reference temperature of 40°C, and to temperatures from -50°C to +16°C for a fluid viscosity of 750 mPa·s.
Values are stated in SI units, which are regarded as standard. This standard was developed in accordance with internationally recognized principles on standardization.
⚠️ Fluids outside the specified viscosity range are seldom used as hydraulic fluids. Mathematical extrapolation to higher or lower viscosity grades may not be appropriate and should be evaluated on its own merit.
⚙️ Viscosity Classification and Measurement
For low-temperature viscosity determination, this practice uses millipascal·second (mPa·s), where 1 mPa·s is equivalent to 1 centipoise (cP). For high-temperature viscosity, it uses millimeter squared per second (mm²/s), where 1 mm²/s is equivalent to 1 centistoke (cSt). Reference test methods include D445 for kinematic viscosity, D2983 for low-temperature viscosity using a rotational viscometer, and D7042 for dynamic viscosity and density.
This practice references several ASTM and SAE standards for testing and classification.
| 🔗 Standard | 📋 Description |
|---|---|
| ASTM D445 | Kinematic Viscosity of Transparent and Opaque Liquids |
| ASTM D2270 | Calculating Viscosity Index from Kinematic Viscosity at 40°C and 100°C |
| ASTM D2983 | Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic Fluids, and Lubricants |
| ASTM D5621 | Sonic Shear Stability of Hydraulic Fluids |
| ASTM D7042 | Dynamic Viscosity and Density of Liquids by Stabinger Viscometer |
| SAE J300 | Engine Oil Viscosity Classification |
| SAE J306 | Axle and Manual Transmission Lubricant Viscosity Classification |
📊 Key Properties and Terminology
Key definitions include hydraulic fluid, kinematic viscosity, Newtonian fluid, and non-Newtonian fluid. Kinematic viscosity is the ratio of dynamic viscosity to density, indicating resistance to flow under gravity. Newtonian fluids exhibit constant viscosity at all shear rates, while non-Newtonian fluids show viscosity variations with shear stress or rate.
💡 Understanding the Newtonian or non-Newtonian behavior of a hydraulic fluid is essential for predicting performance under varying operating conditions.
Additional standards such as E29 for significant digits and E1953 for thermal analysis apparatus are also referenced for proper testing and conformance.
❓ Frequently Asked Questions
🔍 What types of hydraulic fluids are covered by D6080-18?
This practice covers hydraulic fluids based on petroleum, synthetic, or naturally-occurring base stocks. Water-containing hydraulic fluids are excluded.
⚡ What viscosity units are used in this standard?
For low temperatures, viscosity is expressed in millipascal·second (mPa·s), equivalent to centipoise (cP). For high temperatures, kinematic viscosity is in millimeter squared per second (mm²/s), equivalent to centistoke (cSt).
📐 What is the applicable viscosity and temperature range?
The standard applies to fluids with kinematic viscosity from 4 mm²/s to 150 mm²/s at 40°C, and temperatures from -50°C to +16°C for a fluid viscosity of 750 mPa·s.
📌 Which standards are referenced for testing viscosity?
Key referenced standards include ASTM D445 for kinematic viscosity, D2983 for low-temperature viscosity, D7042 for dynamic viscosity, and SAE J300 and J306 for viscosity classification.