Function of hydraulic oil
Energy transmission. Hydraulic oil transfers pressure from the pump to hydraulic motors, cylinders, and other components, ensuring smooth operation of the machinery.
Lubrication. The oil forms a protective film between moving parts, reducing friction and wear.
Cooling. Heat generated within the system is dissipated through the oil, protecting components from overheating.
Corrosion protection. The oil creates a barrier against moisture and oxidation, safeguarding metal parts from rust.
Contaminant removal. Special additives in the oil bind solid particles and deposits, preventing their accumulation in the system.
Hydraulic oil types
Hydraulic oils are divided into several main types depending on their composition, properties, and operating conditions. When selecting hydraulic oil, it is important to follow the manufacturer’s recommendations and consider specific working conditions.
- Mineral-based hydraulic oils. Made from refined petroleum base. Suitable for general-purpose hydraulic systems operating under normal temperature and pressure conditions.
- Synthetic hydraulic oils. Produced through chemical synthesis and offer enhanced performance characteristics. Used in hydraulic systems operating under high pressure, high temperature, or extreme conditions.
- Biodegradable hydraulic oils. Made from vegetable or other biodegradable bases. Used in environmentally sensitive areas such as forestry, agriculture, or near water bodies.
- Water-based hydraulic oils. Applied where fire resistance is required, for example, in metallurgy or mining industries.
- Special additive hydraulic oils. Mineral or synthetic oils enriched with various additives such as anti-wear, anti-corrosion, anti-static, or viscosity stabilizers. Used in specific conditions requiring exceptional properties, such as very high temperatures or high-pressure systems.
- Low-viscosity hydraulic oils. Designed for systems requiring fast oil flow, such as low-load or high-speed systems.
Hydraulic oil types
According to their composition and additives, hydraulic oils are also classified into different types. The most common and widely used in practice are HLP, HV, and HVLP oils. These types contain additional additives that ensure even better oil performance.
- H stands for hydraulic oil.
- V indicates improved viscosity properties under temperature fluctuations.
- L refers to additives that provide resistance to wear, corrosion, and oxidation.
- P denotes additives that protect against wear and high pressure.
Common mistakes when selecting or using hydraulic oil
Incorrect oil selection. This refers to using oils whose characteristics do not match the operating conditions. Oil with improper viscosity cannot form an adequate protective film between moving parts, leading to increased friction and accelerated component wear. Oil with unsuitable composition may also create deposits or foam, clogging filters and hydraulic system channels—this hinders fluid circulation and can damage pumps and valves.
Failure to change oil on time. Oil should be replaced according to the manufacturer’s recommendations. Oil that has lost its additives over prolonged use no longer protects metal surfaces from moisture and oxidation, resulting in corrosion and rust.
Not checking oil level in the reservoir. When the oil level drops, hydraulic pumps may operate irregularly, supplying a mixture of oil and air to the system, or even stop working entirely.
Oil overheating. In a standard hydraulic system, the temperature should be maintained between 50°C and 70°C. When oil overheats, it emits a burnt smell. Causes of overheating may include clogged filters, air in the system, insufficient oil quantity, or equipment operating at an excessive tilt angle.
Failure to replace filters on time. Filters must be replaced according to the operating hours specified in the equipment manual. If filters are replaced too late, oil bypasses the filtration circuit and returns directly to the tank through a safety valve without being filtered. Timely filter replacement extends oil life and improves the reliability of hydraulic system components.
Services provided
Oil replacement
Hydraulic oil is replaced according to the manufacturer’s recommended intervals or when it is found to be contaminated, degraded, or overheated.
Oil filter replacement and cleaning
Filters in hydraulic systems protect against contaminants entering the system. They must be regularly inspected, cleaned, or replaced.
Hydraulic system flushing
Before changing oil or installing new components, the system may be flushed with special agents to remove contamination and old oil residues.
Leak elimination
Hydraulic systems often experience oil leaks due to worn seals, hoses, or fittings. Leak diagnostics and repair are an essential part of service.
System pressure and performance check
Hydraulic oil pressure and temperature are monitored to ensure optimal system operation. Adjustments are made if necessary.
Component maintenance and repair
Includes diagnostics and repair of cylinders, pumps, motors, valves, and other hydraulic components. In some cases, the system must be refilled with new oil after repairs.
Hydraulic oil inventory management
Selection of suitable oil types and ensuring proper storage and usage standards are maintained.
Preventive maintenance
Preventive Maintenance
Oil selection and quality control
One of the most important preventive steps is choosing the right oil according to the manufacturer’s recommendations and specifications. This ensures compatibility with the hydraulic system and effective protection against oxidation, foaming, and corrosion.
Proper oil care
Preventive measures include using oil filtration systems that reduce contamination levels and extend oil life. Regular filter inspection and replacement are essential to prevent solid particles from entering the system. It is also important to monitor oil temperature, as excessive heat accelerates oxidation and viscosity changes.
System cleanliness
Maintaining hydraulic system cleanliness is crucial. During maintenance, proper tools and strict cleanliness standards must be followed to avoid contamination. Even the smallest particles can damage sensitive components such as pumps or valves.
Regular oil condition monitoring, cleanliness assurance, and filtration system use are key steps to keep hydraulic systems efficient and reliable.
To avoid damage, it is essential to use oil that meets the equipment manufacturer’s requirements. It is also important to regularly check oil condition, replace it at specified intervals, and avoid using low-quality or unknown-origin products. Proper hydraulic oil is a critical factor in protecting equipment from failures and ensuring its efficient operation.
