How to lubricate electric motor?
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How to lubricate electric motor?

Views: 0     Author: Site Editor     Publish Time: 2021-09-28      Origin: Site


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After correct handling, electric motor can last a long time. In many cases, the premature motor failure is not due to any design, manufacturing or installation problems, but due to the most fundamental root cause: poor lubrication. In short, many people are killing our motors through bad lubrication practices.

Motor lubrication is not complicated. You only need to choose the correct lubricant, apply the correct lubricant every time, and then apply it at the required frequency.


Choose an excellent lubricant for your electric motor

Precautions of greasing the electric motor

Relubrication frequency of electric motor


(1) Choose an excellent lubricant for your electric motor

The purpose of any lubricant is to separate the moving surface with an oil film. The amount of separation is called the film thickness. If the film thickness is too low, metal-to-metal contact will occur. Too much film thickness and internal agitation will cause fluid friction and temperature rise. To a large extent, the viscosity of the oil (relative to the load and speed of the bearing) determines the thickness of the film. As the viscosity increases, the film thickness increases. Conversely, as the viscosity decreases, the spacing between the filling thickness and the metal surface decreases.

It is important to consider the thickness of the grease. The most common mistake in selecting motor grease is to use multi-purpose grease. Multi-purpose grease is formulated with base oils in the range of ISO VG 220 to 460 cSt, which is too high for motor bearings at typical operating speeds. In order to solve this problem, multi-purpose greases usually contain EP additives. In some cases, EP additives will volatilize and corrode the copper windings of electric motor. Multi-purpose greases are designed for low-speed bearings or high-load bearings, such as pillow bearings used on conveyors. Do not use it for motor lubrication.

In contrast, a well-formulated motor grease usually contains a base oil with a viscosity of approximately 100 cSt at 40°C, a shear and temperature stable thickener (such as polyurea), and a mild anti-wear additive for mixed film lubrication.


(2) Precautions of greasing the electric motor

Pumping grease into electric motor bearings is not complicated. However, some basic precautions should be taken. First, any pipe connecting grease fittings to motor bearings should be pre-filled with grease. Failure to do so may result in no grease entering the bearings in the first few guns, because the grease sprayed from the spray gun is only filling the oil supply pipe. Second, don't worry. Rapidly filling the bearing with grease can cause sudden shocks. It is best to shoot for three to five seconds at a time to ensure that a complete shot is allocated each time.

If equipped, it is good practice to remove the purge port, but it is not necessary to blow out the grease. Machinists often pump grease into electric motor to make the grease flow out of the purge port. Do not use grease that exceeds the calculated amount. Although not always feasible, some motor experts recommend applying grease when electric motor is not running. Since many bearing failures are caused by particle contamination, the best practice is to clean the grease fitting and the end of the grease gun before applying grease to electric motor.


(3) Relubrication frequency of electric motor

Unlike calculating the amount of grease, determining the optimal replenishment interval is slightly more complicated. There are several ways to do this, but the easiest is probably to use Lloyd Tex Leugner in his "Machine Lubrication Practical Manual" (Maintenance Technology International Inc.) For the first time. The Leugner equation uses shaft diameter, rotation speed, and bearing type to estimate the number of hours between relubrication.



As the formula shows, as the speed increases, the number of hours between lubrication decreases because the stress on the lubricant will be higher. In addition to speed, dimensions and bearing working conditions should also be considered.


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