Hydraulic fluids are responsible with transferring power through countless industries and applications. But what goes into creating a performance hydraulic fluid? Afton seeks to answer these questions and provide best-in-class additive technology to meet today and tomorrow's performance needs. View the Afton Hydraulic Additives ►
Hydraulic fluid, at its most basic definition is the medium responsible for lubrication, heat transfer & contamination control for hydraulic machinery. In a more general sense, it’s the fluid that makes it possible to transfer power and protect the equipment doing so. For hydraulic systems specifically, protection comes in many forms and covers; Anti-Wear, Oxidation & Thermal Stability, and Corrosion.
WHAT GOES INTO A HYDRAULIC FLUID?
The final formula of a hydraulic fluid will vary depending on end application & environment. A good breakdown on general component treat rates is:
Component
Type
Percentage Treat Rate
Base Oil
Group I, II, III,
(Group IV, V – Top Tier Oil)
90 - 99%
Viscosity Index Improver
VII
0 - 10%
Additives
Pour Point Depressant
Antifoam Diluent Oil
Detergent/Dispersant
Demulsifier
Friction Modifier
Metal Deactivator
Rust Inhibitor
Antioxidant
Antiwear
0 - 2%
WHAT ARE HYDRAULIC SPECIFICATIONS?
There are many specifications in the hydraulic fluid industry and at first glance it can be a little dizzying with all the acronyms and 6 digit numbers.
The following table breaks down the most common industry & OEM specifications for recommended fluids.
Industry Specs
Pump OEM Specs
ASTM D6158 (HH, HL, HM, HV)
Bosch Rexroth (RDE 90235)
DIN 51524 Part II and III (HLP & HVLP)
Eaton (Vickers) E-FDGN-TB002-E
ISO 11158 (HH, HL,HM, HV, HG)
Parker Denison (HF-0, HF-1, HF-2)
ISO 6743/4 HM and HV
JCMAS HK-1 (Japan)
SEB 18 1222
WHAT HYDRAULIC VISCOSITY IS THE RIGHT VISCOSITY?
There are a few standard ISO grades for hydraulic fluids, so which viscosity is the right one? The standard viscosity grades are broken down below as, ISO 22 VG, ISO 32 VG, ISO 46 VG, ISO 68 and ISO 100VG +. The most important selection factor in viscosity selection is the pump type and if there are relevant specifications. Following that, temperature and operating environment should be considered to make sure the selection fits and delivers expected performance. The infographic below is a simplified guide to the standard ISO grade varieties.
Yes, additives are important to include in the formulation. Assuming the end user is concerned with operating & capital expenses. Without the right combination of additive technology fluid performance will simply not hit the mark. Like any good recipe, if you forget specific ingredients the flavor can drastically change. Click here to View the Afton Additive Technology
Anti-Wear
Prevents wear under high speed conditions. Both ZDDP and ashless phosphorus componentry are used in antiwear hydraulic oils.
Viscosity Index Improver
Keeps oil at the right appropriate viscosity over range of temperatures. Rust and Corrosion Inhibitors Prevent corrosion and rust.
Foam Inhibitors
Prevents foam. These inhibitors generally work by reducing the surface tension between oil and air.
Demulsifier
Encourages oil and water separation, simplifying the filtering processes and extending fluid life.
Antioxidant
Prevents oxidation in the fluid and increases overall lifetime and cleanliness of operation.
Detergent
Keeps metal surfaces clean by absorbing deposits into solution and increasing operating life cycle.
Dispersant
Disperse soot, varnish, and sludge in the oil.
Friction Modifier
Reduces friction (chatter, squeak); reduces micropitting on metal surfaces.
Metal Deactivator
Prevents yellow metal corrosion on sensitive equipment and surfaces.
Ashless
No metals are present in the fluid, promoting environmentally friendly operation in sensitive applications.
Zn-Free
Minimal amount of zinc present (<0.07% wt.)
Zn-containing
The presence of zinc (i.e. Zinc Dialkyl Dithiophosphate (ZDDP))
Hydraulic fluids are expected to deliver reliable performance 24/7 without breaking a sweat, however in the real world there are a few challenges that can present themselves. The most common of these are:
Power Density
Energy Efficiency
Equipment Life
Environmental Impact
Contamination & Filterability
A properly formulated and maintained lubricant will withstand a majority of these challenges, but just like in any industrial there is no such thing as a perfect system.
There are multiple methods that a hydraulic system can fail, and be awaring of each during product development can help prevent poor performance. The most common failure methods for hydraulic systems are:
If any combination of these issues are experienced, it can cause varying levels of inefficiencies or ultimately catastrophic failure. It is vital that the fluid is engineered for the particular environment and operating conditions for the application. By using the right additive technology you can minimize or even eliminate some of the potential risk.
