Why doesn't hydraulics use water? Revealing the core secrets of hydraulic systems
Hydraulic technology is widely used in modern industry, from construction machinery to aerospace, almost everywhere. However, many people may be curious: Why do hydraulic systems usually use oil instead of water as the working medium? This article will combine the hot topics and hot content on the Internet in the past 10 days and use structured data analysis to reveal the answer to this question for you.
1. Basic principles of hydraulic system
Hydraulic system is a device that transmits energy through liquid. Its core is the use of Pascal's principle, that is, in a closed container, the pressure exerted on the liquid can be evenly transmitted to all parts of the liquid. The key components of a hydraulic system include hydraulic pumps, hydraulic cylinders, control valves and hydraulic oil.
| Main components of hydraulic system | Function description |
|---|---|
| Hydraulic pump | Convert mechanical energy into hydraulic energy to power the system |
| Hydraulic cylinder | Convert hydraulic energy into mechanical energy to produce linear motion |
| control valve | Regulate the flow direction, pressure and flow of hydraulic oil |
| Hydraulic oil | Transfer energy, lubricate components, dissipate heat and protect against corrosion |
2. Why does the hydraulic system not use water as the working medium?
Although water seems to be an ideal hydraulic medium (cheap, easily available, and environmentally friendly), in practical applications, water has many problems as a hydraulic medium:
| Compare items | water | Hydraulic oil |
|---|---|---|
| Lubricity | Poor, easy to cause wear of metal parts | Excellent, can effectively protect moving parts |
| Anti-rust and anti-corrosion | Can easily cause metal parts to rust | Contains anti-rust and anti-corrosion additives |
| Viscosity stability | Viscosity changes greatly with temperature | Viscosity is less affected by temperature |
| Cavitation resistance | Cavitation is prone to occur | Good anti-cavitation performance |
| boiling point/freezing point | 0-100℃, narrow operating temperature range | -40℃ to above 200℃, wide working range |
| Sealing adaptability | High sealing requirements and easy to leak | Lower requirements for sealing materials |
3. Special application scenarios of water
Although water is not an ideal choice in most hydraulic systems, there are still applications for water-based hydraulic systems in some special situations:
| Application areas | Reason for use | solution |
|---|---|---|
| food processing | Prevent oil contamination of products | Use a special water-glycol solution |
| Mining machinery | High fire protection requirements | High water content hydraulic fluid (HFA) |
| Marine Engineering | Environmental considerations | Biodegradable hydraulic oil |
4. Development Trend of Hydraulic Oil
With the improvement of environmental protection requirements and technological advancement, hydraulic oils are also constantly evolving:
| Development trend | Technical features | Representative products |
|---|---|---|
| Biodegradable | Reduce environmental pollution | Vegetable oil based hydraulic oil |
| Long life | Extend oil change intervals | Synthetic hydrocarbon hydraulic oil |
| High cleanliness | Reduce system wear and tear | Nano filter hydraulic oil |
| Multifunctional | Has multiple functions such as lubrication and cooling | Multi-effect hydraulic oil |
5. Key points in hydraulic system maintenance
In order to ensure the long-term stable operation of the hydraulic system, the following maintenance points cannot be ignored:
| maintenance items | Recommendation cycle | Things to note |
|---|---|---|
| Hydraulic oil replacement | 2000-5000 hours | Depends on working conditions and oil quality |
| Oil filter replacement | 500 hours or pressure difference alarm | Use original filter element |
| Moisture detection | quarterly | Moisture content should be <0.1% |
| Acid value testing | every six months | Acid value increase <0.5mgKOH/g |
| Particle pollution degree | quarterly | NAS level 9 or better |
6. Conclusion
To sum up, the reason why hydraulic systems do not use water but use hydraulic oil as the working medium is mainly because hydraulic oil has obvious advantages in lubricity, anti-rust and anti-corrosion, and viscosity stability. Although water has the advantages of being cheap and environmentally friendly, its technical limitations make it difficult to meet the requirements of most hydraulic systems. As technology advances, more high-performance water-based hydraulic fluids may appear in the future, but for the foreseeable future, mineral oil-based and synthetic hydraulic fluids will remain the mainstream choices for hydraulic systems.
When selecting hydraulic oil, engineers need to comprehensively consider various factors such as equipment requirements, working environment, temperature range, and economy to ensure efficient and reliable operation of the hydraulic system. At the same time, regular maintenance and oil testing are also key to extending the life of the hydraulic system.
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