Lubricants and Friction
Lubricants act to reduce friction. Now, this makes it easier to keep machines running smoothly, and it cuts down on the amount of heat and wears caused by friction. A machine’s moving parts generally experience three types of friction.
- Sliding Friction
- Rolling Friction
- Fluid Friction
Sliding friction occurs when two surfaces in contact slide past each other. This type of friction offers the most resistance to motion. So machinery is usually built to minimize or eliminate it. Building a machine to minimize sliding friction is to place rolling elements between the moving surfaces. This is the principle behind rolling contact bearings. Rolling contact bearings experience rolling friction that is considerably less severe than sliding friction. Still, they must be properly lubricated to reduce heat and wear.
The useful life of a rolling contact bearing or anti-friction bearing would be drastically shortened if the bearing were operated dry.
Another way to build a machine to reduce friction is to separate two sliding surfaces by a lubricant film. As long as the surfaces do not touch, sliding friction is eliminated. There’s still some fluid friction within the lubricant, but it’s much less than sliding friction. Fluid friction is the resistance to motion within a fluid, and it’s not as obvious as other types of friction.
Lubricants are made from one of four groups of materials or medium.
Originally animal and vegetable lubricants were the most widely used. Still, they’ve been almost completely replaced by mineral and synthetic types. But whatever lubricant you use, to get maximum benefits from lubricants we need to use a proper lubrication system.
What is a lubrication system?
An automatic lubrication system, also known as a centralized lubrication system, is defined as a controlled and precise amount of a specific lubricant that is delivered to a specific location at a specific time when the machine is running.
Reasons for using a lubrication system
The study says that in plant maintenance, lubrication cost is approx. 3% of the total cost of maintenance budget, but lubrication-related activities could reach up to 40% of the total maintenance budget. If one needs to achieve optimum reliability & maximum benefits from the Lubrication system, the following factors must be considered.
The Right Lubricant
The proper lubricants selection for proper application is vital to get maximum benefits from the lubrication system. Normally right lubricants selection can depend on four factors of applications.
Neither less quantity of grease is good nor high quantity. An increase qty of grease can increase temperature & friction inside the bearing & can decrease the efficiency or lifetime of bearing lead to failure. Only measured lubricant qty reached to lubrication point so, no wastage of lubricants hence lubrication cost reduce.
At Right Time
Lubricants will effectively reduce friction & wear if supplied at the right timing with proper re-lubrication interval.
At Right Point
Grease or oil should reach the right point where friction & wear is high. If it does not reach the friction point, then it will be of no use.
Types of lubrication systems
Different types of lubrication systems have been designed and developed over the years based on the specific requirements of the instrument and the different industrial sectors. We are talking about the most popular and beneficial lubricant systems used by different plants in different industrial sectors.
Oil Lubrication System
The oil lubrication system is also known as the loss lubrication system. In this system, oil or liquid grease produces a thin oil film that protects the parts. It is renewed at regular intervals by an automatic lubrication system with an electric oil pump. The main systems used in oil lubrication are single-line systems and 33V systems.
Splash Lubrication System
In these types of lubrication systems, the lubricating oil accumulates in an oil sump. Most small four-stroke petrol engines use splash lubrication. On horizontal crankshaft engines, a dipper on the bottom of the connecting rod scoops up oil from the oil sump for the bearings. When the engine runs, the dipper dips in the oil once in every crankshaft revolution and causes the oil to splash on the cylinder walls.
Recirculating Oil System
The purpose of oil recirculation is to supply lubrication and provide cooling to bearings and gears. An electric pump ensures that an appropriate lubricant pressure is available in the mainline, where the oil flow is also measured and regulated.
Air-Oil Lubrication System
This system consists of a controlled air-oil stream utilized to cool and carry small quantities of air-oil particles to the lubrication points. It is suitable for large machines in heavy industry and machine tools.
Air Oil lubrication system is the optimal solution for economical and reliable lubrication of bearings. The bearings have a longer service life, and thus high production availability is attained.
Grease Lubrication System
In this system, the greasing pumps provide a proper amount of grease to the lubrication points. The main systems used for grease lubrication are Dual Line and Progressive systems.
Dual Line Lubrication Systems
The dual-line system has a modular design that allows easy configuration and expansion of the system. It is suitable for industries with large machines and many lubrication points.
SKF has developed a Dual Line Lubrication system. These flexible systems are simple to design and can be reduced easily by removing metering devices or extended by installing additional metering devices. You can know more about the Dual Line Lubrication system by watching the video.
Progressive Lubrication systems
For small to medium-sized machines that require continuous lubrication, a progressive lubrication system will best suit them. Progressive systems provide uninterrupted lubrication as long as the pump is turned on. Once the pump is turned off, the pistons of the progressive metering device will stop at their current position. When the pump starts supplying lubricant again, the pistons will move to where they were left.
MQL (Minimum Quantity Lubrication) System & Near Dry Machining
An innovative new technology that replaces traditional and pure oil-liquid systems in a machining environment. A controlled compressed air flow carries minimal cutting oil in an “aerosol” format to the cutting surface by external or internal (through equipment lubrication). MQL is a little bit bigger of an umbrella than near dry machining. MQL can be applied to multiple manufacturing operations like sheet metal forming operations, blanking, forming, cutting, etc. Near dry machining is more specific to machining operations such as mills, drills, turning operations, and tapping.
Wet Sump Lubrication System
In wet sump lubrication systems, the oil is transported to different engine parts with the help of a sump strainer, and the oil pressure is about 4 to 5 kg / cm2. After lubrication, the oil is again taken to the oil sump. In this case, the oil is present in the samp. Therefore, it is called a wet sump lubrication system.
The advantage of the wet sump system is its simplicity. And machine parts are near where the lubrication will be applied through lubricating oil, there are not many parts required, and it is relatively safe to make in the car.
Dry Sump Lubrication System
A dry-sump lubrication system is particularly used in racing cars, and it has additional components to the wet-sump lubrication system. These components include an oil tank with a breather tank. Furthermore, the dry-sump lubrication has a cyclone separator and a multi-stage pump. Check out the video to know more about the Dry Sump Lubrication system.
So, we have covered different types of lubrication systems used in different applications to achieve the maximum benefit of lubrication. Except achieving max benefit, there are multiple benefits are there of the automatic lubrication system.
Benefits of using a lubrication system
- Easy access: All important components of the machine can be oiled, regardless of criticality and location. This ensures safe machine operation and reduces the risk of undefined lubricating components by maintenance personnel.
- Increase the machine’s efficiency: In a centralized lubrication system, lubrication occurs when the machine is running so that the lubricant is distributed evenly across all friction points and increases the efficiency of the overall machine performance, less breakdown, less downtime, and replacement cost.
- Reduced energy consumption: In centralized or automatic lubrication, the system as lubricant reaches the friction point at the right time, in the right amount so low friction, energy consumption is lower, and overall machine operation cost is lower.
- Cleanliness: Lubricant contamination with the effect of foreign particles carries the overall performance and life. Avoiding grease contamination in manual lubrication systems can be a challenge for every maintenance person. However, through an automatic lubrication system, we can avoid contamination of lubricants and achieve cleanliness. In an automatic lubrication system, an automatic lubricant can provide an uninterrupted and accurate flow of fresh and clean lubricant at the lubrication points.
The article is written by Riya Veluri, an editorial team member of Industrial Lubricants. After her graduation, Riya works as a website developer & SEO specialist in Lubrication & Tribology Industry & writes technical articles on Lubricants, Lubrication, Reliability & sustainability.