Historically, hydraulic systems have used mineral oil-based hydraulic fluid because of its lubricity, energy density, and stable operating characteristics under pressure. However, there are numerous reasons for OEMs to be uncomfortable with hydraulic fluid – not least the risk of environmental toxicity, and the workplace safety implications should a leak occur. These concerns have fuelled a search for water-based or sustainable hydraulic technology; one of the most interesting developments emerging in the sector in recent years. Read on to find out more.
What is water-based hydraulics?
Water hydraulics is not a new concept. The word hydraulic itself is derived from the Greek words hydro (water) and aulos (pipe or tube) – so, literally ‘water pipe’, with no oil required. Over time, however a ‘hydraulic system’ has grown to mean any fluid power network that uses a pressurised fluid to generate force, motion, or power, and in modern systems this fluid is typically a petrochemical oil.
So, water-based systems existed long before oil-based systems came to dominate, and modern materials and fluid conditioning methods have started to make them viable once more. As sustainability becomes a stronger priority across the heavy machinery, offshore engineering, and manufacturing sectors, water, or a water-glycol mix, is re-emerging as a realistic medium for power transmission.
Why use water as a hydraulic medium?
Water is clean, abundant, and non-flammable. Unlike mineral oil, there is minimal environmental impact if leaked, and in many cases, water requires a less complex containment infrastructure. These benefits have attracted attention in several sectors, including:
- Marine and offshore environments
- Food and pharmaceutical production facilities
- Forestry and environmentally sensitive land applications
- Fire risk areas such as foundries and underground mines
However, there are several challenges to water-based hydraulics. Firstly, water lacks the lubricity of oil and also causes a higher corrosion risk to metal components. Modern systems must compensate by using stainless steel components, corrosion-resistant coatings, and specialised water-glycol or seawater-compatible formulation to maintain equipment life.
Secondly, water-based hydraulics doesn’t always have the same power differential as oil-based applications, and this comes down to how the fluid behaves inside the system. Both systems rely on Pascal’s law, meaning that either fluid can generate high force when pressurised. So, in theory, a water-based hydraulic circuit could deliver equal mechanical output to an oil-powered alternative if the system pressure was comparable and the flow rate sufficient. However, in practice water-based systems have a lower power density in most applications, and also struggle to achieve the same operating pressure. This means that that oil-based systems generally perform better at high loads.
How water-based hydraulic systems work?
Water hydraulics operate on the same fundamental principles as traditional oil-based systems: pressure applied at one point is transmitted through the fluid to generate mechanical force elsewhere. The main difference lies in component design and fluid handling strategy.
A typical water hydraulic circuit may include:
- Stainless steel pumps, pipe clamps, diverter valves, and cylinder components designed to reduce corrosion
- Ball valves and control valves engineered for low viscosity fluids
- Additive-treated water glycol blends to improve lubrication
- High-pressure seals compatible with water glycol mixtures
- Monitoring systems to manage temperature, cavitation, and fluid quality
- Ceramic-coated plungers, pistons, and valve surfaces
- Precision-finished bores to minimise frictional losses
- In-line filtration to remove dissolved solids and corrosion debris from the fluid
Because water is less compressible than oil, response speed can be faster and positional accuracy can improve. However, materials and tolerances must be carefully selected to prevent wear under poor lubrication conditions. Some water-based systems also incorporate diverter valves to shift flow between low-pressure cooling circuits and high-pressure working circuits, allowing water to serve dual functions without additional media.
What next?
Oil-based hydraulic systems generally remain superior for high pressure and high torque workflows, and systems that require long-interval lubrication stability. However, for environmentally sensitive applications and plant used in high hygiene environments, water driven systems could be a good alternative.
To find out more or to discuss your needs, feel free to call one of our experts today on 01353 721704.
Image Source: Canva