What is lubricating oil?
Lubricating oil is a liquid lubricant, having various additives for properties fit for use purposes based on the raw materials of base oils. Base oils can be classified into mineral oil, fatty oil, and synthetic oil. Due to the advantages in quality, durability, performance, and price, mineral oils are popular. Uses of fatty oils and synthetic oils are limited to special purposes.
Effects of lubricating oils
1) Gamma effect
Formation of oil film on metal surface reduces friction of the moving part, which is the most important effect of lubricating oil.
2) Cooling effect
If heat generated from the lubricating area and delivered from the outside is accumulated and becomes very hot, it causes fatal damage to the facility as well as accelerates degradation of lubricating oil. Thus, the heat generated should be absorbed quickly and discharged to the outside.
3) Stress dispersion effect
Wide dispersion of the pressure applied to the lubricating area prevents wear resulting from high local pressure.
4) Sealing effect
Lubricating oil in the closed system chokes up fine cavities between two mechnical elements, preventing lubricating oil leakage, maintaining the pressure in the machine, preventing penetration of foreign substances.
5) Clean dispersion effect
Lubricating oil prevents deposits and adhesion in the facility of solid sludge produced by inclusions of oxidation products, water, dust, and incomplete combustibles resulting from the long use of lubricating oil, dispersing existing oxidation products and sludge into fine particles in the lubricating oil.
6) Rust proof effect
Lubricating oil prevents rust on metal surface caused by oxygen, water or corrosive gas in the air.
Additives to lubricating oil
1) Anti-oxidant
It prevents oxidation of lubricating oil by oxygen in the air, thus preventing production of corrosive acid or sludge.
2) Clean dispersing agent
It prevents sediment and adhesion of sludge produced by oxidation products generated under high temperature operating conditions and foreign substances penetrating from the outside, acting to disperse existing oxidation products and sludge into fine particles in the lubricating oil.
3) Viscosity index improver
It increases viscosity index and reduce viscosity change depending on the temperature.
4) Liquidity reinforcing agent
When lubricating oil is at low temperature, wax ingredients in the lubricating oil are precipitated to hinder the flow of lubricating oil. This agent acts to improve low temperature liquidity by preventing solidification of wax ingredients.
5) Extreme pressure additive
If oil film is broken under high load and the contact between metals occurs, it acts with metal surface to form a new extreme pressure film, preventing direct contact between metals.
6) Oiliness improver
If sufficient oil film cannot be formed by lubricating oil viscosity only, it acts to reduce friction coefficient by being absorbed physically and chemically onto the metal surface.
7) Anti-rust additive
It forms film on the metal surface, preventing contact with air or water, preventing rust on the metal surface.
8) Anti-former
It quickly removes foam generated by various causes, preventing oil film breakage by foam, protecting facilities.
Causes of degradation
1) Inclusion of blow-by gas
Most exhaust gas is to be discharged, but some comes into the oil pan through the gap between piston ring and cylinder. The inclusion of this gas has many adverse effects on lubricating oil degradation.
2) Inclusion of water
Water in the blow-by gas, water leakage from the cooling system, and water from the outside may flow in. Water inflow may form low temperature sludge, cause rust and corrosion, and, in case of a plenty of water, may bring engine bake due to oil film breakage.
3) Inclusion of metal wear powder and dust
Especially, SiO2, A12O3, and Fe2O3 in the atmosphere dust have adverse effects on wear of the cylinder liner and piston ring.
4) Degradation of lubricating oil
Oxidation of engine lubricating oil is accelerated under the condition that a lot of acid gas comes in and metals as a catalyst exist. Actually engine inside suffices this condition, oxidation is accelerated in case of high loaded continuous operation.
5) Consumption of additives
Additive mixtures to maintain appropriate quality to use purposes and conditions and to prevent engine corrosion are consumed with the progress of service period, and if the contents are lower than the threshold value, performance decline of lubricating oil develops rapidly.
Problems caused by oil degradation
- Irregular machine operation due to valve choking
- Cavitation
- Cooling effect hindrance of a cooler
- Wear increase
- Acceleration of sludge deposition
- Control inhibition of a pump, valve, and cylinder
- Wear of a pump and valve
- Rust in the piston rod and ram cause wear and oil leakage increase
Contamination control of lubricating oil
- Survey of contaminants
- Understanding on contamination effects
- Measures to prevent contaminants inclusion
- Measures to remove contaminants
- Installation and care of a purification device
- Measurement of contamination of in-service oil
- Setting of contamination control standards
Contamination prevention
1) External contamination prevention
Attach a packing gasket to the joint connection, and a filter and air breather to the oil supply inlet.
2) Considerations for the tank
- Attach a suitable strainer
- Install a suitable baffle plate
- Install the return pipe below the oil level, at more than 3 times height of a pipe diameter above the tank bottom
- Install the suction pipe at over 50 mm above the tank bottom
- Install the drain cock
- Hydraulic tank bottom should have a slope
- Attach a by-pass purification device to the tank
- Install a magnetic filter on the tank bottom
Determination of in-service oil degradation
Most required data for periodic analysis of in-service oils are operating time, oil temperature, refueling quantity, cleaning state, and operating state of the lubricating oil.
1) Direct determination
- Ensure to understand the properties of the new oil in advance.
- Collect the representative specimen of in-service oil and examine the properties.
- Compare and review properties of the new oil and in-service oil, set control standards, and replace.
2) Simple determination
- Put oil into the transparent glass test tube, project it toward the light, and rough evaluation is possible.
- Clear : Good (Then, oil's own color is irrelevant)
- Hazy : Contaminated (test and analysis required)
- Red and Black : Oxidation (test and analysis required)
- Emulsion : Water (immediate replacement with the new oil required)
- Smell an oder to determine the inclusion of fuel oils or contents of impurities.
- Dip the hand into oil to determine the viscosity and the size of impurities.
- Put a proper amount of oil into the test tube, heat the fore-end up to 110℃, and you can determine the presence of water with the
sputtering sound.
- Put oil and water in the same amount into the test tube, stir it severely, and leave it until oil and water is completely
separated. Measure the separation time to check the demulsification.
- If there is a simple visco meter, neutralization number tester, hydrometer, or colorimeter, use any or other simple testers.
Prevention of lubricating oil degradation
To prevent in-service lubricating oil degradation, maintain economically sound lubricating state, and extend its life, we need to clean the circulation system at all times as well as to remove causes accelerating lubricating oil oxidation, while replacing with or supplying a new oil at a proper time as well as rapidly removing impurities and oxidation products in lubrication. Cautions to prevent degradation are as follow :
- Avoid high temperature if possible.
- Avoid use of oil mixtures to maintain stable additive reaction and proper viscosity
- Clean a new machine sufficiently before use. (Remove steel chips, rust powder, or rust inhibitors)
- Remove completely degraded oils in case of replacement.
- Remove rapidly any inclusions of impurities (water, dust, metal wear powder, fuel oil, etc)
- Clean about one time a year to maintain clean circulation system.
Features and Advantages
Possessing proven technology and knowhow
- Sung Kyung System is the leading company which launched the industrial oil filtering system first out of the domestic companies.
- Possessing knowhow and technology based on experiences with many customers under diverse environments.
Partnership building with diverse customers
- Possessing experiences in actual design and management of products proved by many customers under diverse corporate environment.
- Solid partnership building with domestic/overseas advanced companies to have diverse products in accordance with diverse requirements
of customers.
Possessing diverse product groups selectable to customer needs
- Offering diverse products according to budgets and needs from low end and high end systems.
- Responding to requirements of clients with diverse kinds of products.