11 Ways To Lubricate Bearings

The lubrication of bearings is crucial for their smooth operation, preventing direct contact between the raceways and rolling elements, reducing friction and wear, extending lifespan, enhancing performance, and preventing rust and corrosion from foreign particles. This article outlines 11 common lubrication methods for bearings, aiming to assist in your work and learning.

Manual Lubrication: 

The simplest method, where oil is manually supplied using a grease gun when lubrication is insufficient. However, it's challenging to maintain a consistent oil level, and there's a risk of forgetting to lubricate. This method is typically used for light-load, low-speed, or intermittent applications.

Drip Lubrication: 

Suitable for bearings with peripheral speeds below 4-5m/s, where lubricating oil is supplied in approximately fixed quantities through containers, tubes, needles, or valves. The classic method is using an oil drip cup, with the oil drip rate varying significantly depending on oil viscosity, bearing clearance, and oil supply hole position.

Oil Ring Lubrication: 

Utilizes a rotating ring mounted on the shaft to transfer lubricating oil from a reservoir to the bearing (only applicable for horizontal shafts). It's suitable for medium to high-speed bearings with shaft diameters larger than 50mm, with the ideal seamless oil ring. For a bearing width-to-diameter ratio less than 2, one oil ring can suffice; otherwise, two oil rings are required.

Oil Wick Lubrication: 

Relies on capillary action and siphoning of oil from a cup to the bearing through oil-soaked wicks. Mainly used for light-load and medium-load bearings with peripheral speeds below 4-5m/s, with the added benefit of filtration throughout the process.

Oil Pad Lubrication: 

Uses capillary action of oil pads to apply lubricating oil from a reservoir onto the shaft surface. This method ensures constant cleanliness of the friction surfaces but may suffer from insufficient oil supply due to dust blocking capillary pores. Typically, the oil supply volume in oil pad lubrication is only 1/20 of oil lubrication.

Oil Bath Lubrication: 

Involves partially immersing bearings in lubricating oil, commonly used for vertical thrust bearings but not suitable for horizontal radial bearings.

Splash Lubrication:

Relies on the splashing action of rotating components in an oil tank to supply lubricating oil to the bearings, suitable for higher-speed bearings.

Spray Lubrication: 

Involves atomizing lubricating oil and spraying it onto the friction surface, suitable for high-speed bearings.

Pressure Lubrication: 

Lubricating oil is supplied to the bearings under pressure by lubrication pumps, with the oil flowing out of the bearings collected back into the reservoir for recycling. It's the most stable and highest volume lubrication method, suitable for high-speed, heavy-duty, and critical sliding bearings.

Circulating Oil Lubrication: 

Filtered oil is pumped into bearing components, and the lubricating oil that passes through the bearings is filtered and cooled before reuse. Due to the ability of circulating oil to carry away heat, cooling the bearings, this method is suitable for high-speed bearing components.

Jet Lubrication: 

High-pressure oil is pumped through nozzles into the bearings, with the oil flowing into the bearings and then into the oil sump from the other end of the bearing. When bearings rotate at high speeds, the rolling elements and cages create an airflow, making it difficult to deliver lubricating oil using conventional methods. Therefore, high-pressure jetting is necessary, with the nozzle positioned between the inner ring and the cage.

Bearing lubrication is an ongoing task, with the oil change interval based on the bearing's operating conditions and oil quantity. Typically, in environments with temperatures below 50°C and minimal dust, oil should be changed once a year. However, if the oil temperature reaches 100°C, it should be changed every three months or even sooner.