Dynamic Model Predicts Grease Relubrication Interval

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Solution Overview

Problem

Current methods for predicting the relubrication interval of grease-lubricated rolling element bearings are limited by their reliance on empirical models and laboratory tests conducted under severe conditions, which fail to accurately predict grease life under normal operating conditions, resulting in unpredictable bearing failures.

Innovation Solution

A method and device that measure parameters indicative of lubricant film breakdown, such as temperature and capacitance, to construct a dynamic model that predicts the relubrication interval by analyzing time series data and extrapolating future events, allowing for accurate prediction of when a grease will reach an unacceptable condition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If laboratory performance tests are conducted under severe conditions (high temperature, high speed, high load), then the time required to evaluate grease performance is reduced, but the ability to predict grease life under normal conditions is limited

Engineering Contradiction:
Improvetesting timeVSAvoidprediction accuracy
Core Design Contradiction:
Loss of timeVSReliability

Solution Approach 1:

The invention changes the testing parameters from severe laboratory conditions to normal operating conditions. By conducting tests at typical operational speeds, temperatures, and loads, the grease life prediction becomes reliable for actual service conditions while still providing actionable data within acceptable timeframes.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The invention creates a simplified model that copies the essential behavior of grease under normal conditions rather than attempting to replicate complex severe conditions. This model captures the critical lubrication mechanisms that occur during normal operation, providing accurate predictions without the time penalty of severe condition testing.

Inventive Principle:
Principle #26Copying

2Quantity of substance

If conventional grease testing methods are used, then statistical data is obtained, but no prediction can be made about the relubrication interval for a specific individual bearing

Engineering Contradiction:
Improvestatistical dataVSAvoidindividual bearing prediction
Core Design Contradiction:
Quantity of substanceVSMeasurement precision

Solution Approach 1:

The invention implements feedback mechanisms that continuously monitor individual bearing performance parameters (temperature, vibration, lubrication levels) and adjust predictions in real-time. This allows the system to provide personalized relubrication predictions for each bearing based on its actual operational state rather than relying solely on statistical averages.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The invention segments the bearing population into individual units, each with its own monitoring and prediction system. By treating each bearing as a distinct entity with unique operational characteristics, the system can provide precise individual predictions while still maintaining statistical context through aggregated data analysis.

Inventive Principle:
Principle #1Segmentation

3Reliability

If grease life tests are extended to match actual grease life duration, then prediction accuracy under normal conditions improves, but testing costs increase

Engineering Contradiction:
Improveprediction accuracyVSAvoidtesting duration
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The invention performs preliminary analysis of grease behavior under normal conditions to establish baseline performance characteristics. By conducting shorter tests that capture the essential lubrication mechanisms early in the grease life cycle, the system can predict long-term performance without requiring extended testing durations.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The invention employs dynamic modeling techniques that capture the time-varying behavior of grease under normal operating conditions. By focusing on the dynamic characteristics and rates of change rather than absolute time durations, the system can make accurate long-term predictions from shorter test periods.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentUS8718991B2Prediction of relubrication interval
Publication Date: 2014.05.06 AB SKF SKF PATENT DEPARTMENT
  • US8718991B2 patent drawing
  • US8718991B2 patent drawing
  • US8718991B2 patent drawing

AI summary

The invention relates to a method of predicting when a grease in a grease-lubricated rolling element bearing (10) will reach an unacceptable condition. According to the invention, a time series of a parameter is measured and recorded, whereby the parameter is directly or indirectly indicative of a degree of breakdown of a lubricant film separating the rolling contacts. With the aid of processing means (22), the time series is analyzed, a dynamic model is constructed that predicts the evolution of parameter values, and the model is used to extrapolate the time series. A time at which a predefined limit will be exceeded is then determined from the extrapolated time series, whereby the predefined limit is representative of unacceptable grease condition. The method according to the invention can be used to predict a relubrication interval for an individual grease-lubricated bearing.