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Know Your Vertical Motor Thrust Bearings

10/09/2019

Vertical High ThrustOne of the biggest differences between horizontal motors and vertical motors is the bearing arrangement. Typically, the bearing arrangement inside a vertical motor consists of one or more thrust bearings and a guide bearing. The thrust bearing is commonly mounted on the top of the motor and the guide bearing is located on the bottom. The typical thrust bearings found in a vertical motor are one or more angular contact bearings, a spherical roller bearing, or a hydrodynamic plate bearing, lubricated in an oil bath reservoir. The axial force is either upward, downward or balanced, and is generally the factor used to size the thrust bearing. As the thrust becomes greater, the bearing size or quantity of bearings normally increases.

When sizing a vertical motor’s thrust bearing for a new application, the first step is to figure out the amount of down thrust and up thrust the bearing(s) will need to handle. Once you have that number, you generally can work with your local bearing supplier to ensure that you install a bearing that has more than enough capacity to handle the required axial thrust. It’s very important to not under size the bearing. Under sizing the thrust bearing can cause premature failure and lead to even bigger problems such as rubbing of the stator and rotor, destruction of the bearing housing and even melting of the babbitt from hydrodynamic thrust bearings.

It’s always important to properly lubricate the bearings inside the vertical motor. Using the correct viscosity in relation to the ambient temperature is one of the most crucial aspects of proper bearing lubrication. If the oil has a high viscosity, fluid shear will occur causing the temperature to rise excessively leading to accelerated degradation of the oil. If the oil's viscosity is too low, it won't be able to maintain separation of the rolling elements and races, causing extensive bearing damage. Good lubrication practices include never mixing oils, follow the manufacturer's recommendation for oil type and routinely check for contaminants in the oil.

 

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Geoffrey Brewer

HECO - All Systems Go

269-381-7200

gbrewer@hecoinc.com 

 

About the author:

Geoffrey Brewer  is the Director of New Equipment Distribution at HECO - All Systems Go. Geoffrey lead HECO's team on replacing motors with new or surplus options. From NEMA T-Frame motors to large, custom Above NEMA frame motors, Geoffrey and his team lead the charge for HECO.

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