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Bearing Relubrication Quantity and Frequency Standard

1.0  Purpose

This document details the method to calculate relubrication quantities and frequencies for rolling element bearings and linear bearings.

2.0  Scope

This standard covers production and utility equipment in General Mills facilities.

3.0  Standard

Proper lubrication of bearings is essential to ensure reliability of equipment within General Mills facilities. Two main components of proper lubrication are Right Time and Right Amount. In order to lubricate bearings with the right amount of grease at the right time, General Mills has developed a bearing relubrication calculator, based in Microsoft Excel. This calculator is based on technical data from Noria, SKF, Dodge, Thomson, as well as other bearing and lubrication resources.

4.0  Rolling Element Bearings

4.1  Relubrication Frequency

To calculate the time between relubrication in hours, the following equation is used:

Where:

T = Time between relubrication in hours

Kn = Product of correction factors

Kb = Bearing type factor

n = Rotational speed (rpm)

d = Bearing inside diameter (mm)

The calculator has a maximum time of 32,000 hours based on the service life of grease.

4.2  Relubrication Quantity

The quantity for relubrication is based on the following equations:

G(ounces) = D(in) x B(in) x 0.1 -or- G(grams) = D(mm) x B(mm) x 0.005

Where:

D = Bearing outside diameter

B = Bearing width

5.0  Linear Bearings

5.1  Relubrication Frequency

To calculate the time between relubrication in hours, the following equation is used:

Where:

T = Time between relubrication in hours

Kn = Product of correction factors

Fc = Correction factor (metric = 1666.67, imperial 656.168)

Ls = Stroke length (total travel forward + reverse per cycle in cm or in)

C = Cycles per minute (1 cycle is forward + reverse motion)

The calculator has a maximum time of 32,000 hours based on the service life of grease.

5.2  Relubrication Quantity

The quantity for relubrication is based on the following equation:

Where:

G = Grease amount (g or oz)

OD = Outside diameter (mm or in)

ID = Inside diameter (mm or in)

L = Bearing length (mm or in)

Fc = Correction factor (metric = .000088, imperial = .050867)

6.0  Correction Factor Tables

The following correction factors are used to de-rate the frequency based on actual operation conditions. These tables apply to both rolling element bearings and linear bearings.

Bearing Temperature Correction Guidelines - Kt
Temperature Range (oC) / Temperature Range (oF) / Factor
Less than 70 / Less than 158 / 1
70 - 85 / 158 - 185 / 0.5
85 - 100 / 185 - 212 / 0.25
100 -115 / 212 - 239 / 0.125
115 - 130 / 239 - 266 / 0.0625
130 - 145 / 266 - 293 / 0.03125
145 - 160 / 293 - 320 / 0.015625
160 - 175 / 320 - 347 / 0.007813
Greater than 175 / Greater than 347 / 0.003906
Contamination Correction Guidelines - Kc
Contamination Guidelines / Examples / Factor
Light, non-abrasive dust / Warehouse, Utility Applications / 1
Heavy, non-abrasive dust / Packaging Material Dust, no sugar, no starch, no calcium / 0.7
Light, abrasive dust / Sugar, Starch, Calcium Applications / 0.4
Heavy, abrasive dust / Sugar, Starch, Calcium Applications / 0.2
Moisture Correction Guidelines - Km
Moisture Guidelines / Examples / Factor
Humidity mostly below 80% / Dry packaging, utilities, material handling / 1
Humidity between 80% - 100% / Processing areas, soup/cereal processing / 0.7
Occasional condensation / Light washdown, water splash, outdoor equipment / 0.4
Occasional water on housing / Wet wash applications, direct water spray / 0.1
Position Correction Guidelines - Kp
Position Guidelines / Factor
Horizontal shaft orientation / 1
Angled shaft orientation / 0.75
Vertical shaft orientation / 0.5
Vibration Correction Guidelines - Kv
Vibration Guidelines / Factor
Less than 0.2 ips velocity, peak / 1
0.2 to 0.4 ips / 0.6
Above 0.4 ips / 0.3
Unknown / 0.6
*use vibration pen or vibration analyzer if needed
Load Correction Guidelines - Kl
Load Guidelines / Factor
Light loads / Conveyor bearings, motors, HVAC, continuous packaging equipment / 1
Moderate Loads / Intermittent packaging equipment, roll stands, centrifugal pumps, blowers / 0.5
Heavy Loads / High viscosity mixers, flaking rolls, vibratory equipment, fork truck wheels / 0.2

The following tables of correction factors apply to rolling element bearings only.

Bearing Type Factor
Bearing Type / Factor
Spherical or Thrust Bearing / 1
Cylindrical, Needle, Tapered Bearings / 5
Ball Bearings / 10
Ring Rotation Correction Guidelines - Kr
Ring Rotation Guidelines / Factor
Inner ring rotating / 1
Outer ring rotating / 0.6
*Inner ring rotation is default

© General Mills 2015