The Basics of Condition Monitoring: A Comprehensive Guide

What is Condition Monitoring?

Condition Monitoring has become a widely recognized practice in the industrial equipment sector. To put it simply, it involves regularly monitoring various parameters such as vibration, temperature, ultrasound, oil condition, current, pressure, and voltage. The data obtained from this monitoring is recorded and analyzed to track trends.

In essence, Condition Monitoring is a crucial aspect of Predictive Maintenance or Condition Based Maintenance. The ability to predict faults relies on having prior indications. Condition Monitoring alone is insufficient; it must be integrated with Preventive Maintenance and/or Corrective Maintenance to be effective. Without this integration, it would be more appropriate to call it Condition Assessment. To ensure effectiveness, a comprehensive PdM/CBM plan should include Condition Monitoring as a key component.

Condition Monitoring involves the periodic monitoring of various conditions and properties of assets in industries. These assets include machines, equipment, infrastructure, manufacturing processes, and electronics found in industries. Machines can be either rotating or reciprocating, such as motors, gearboxes, compressors, pumps, and blowers. Equipment can be static, like heat exchangers, transformers, electric panels, pressure tanks, boilers, refractory, ovens, battery banks, and capacitor banks. Dynamic equipment includes steam traps and valves. Infrastructure includes compressed air pipelines, insulated pipelines, steam pipelines, power cables, fabricated structures, equipment/machinery structures, foundations, and RCC building structures. Processes can include paper manufacturing processes in paper mills, texturizing processes, and glass manufacturing processes. Electronics can refer to electronic circuit boards found in control panels. Condition monitoring allows for the continuous monitoring of the condition of each equipment, machine, process, and infrastructure in any type of industry.

What are the advantages of Condition Monitoring?

The benefit of condition monitoring is only to learn about the fault threshold, which means we will get to know about the fault inception at an early stage. The result of the condition monitoring process is just a trend chart and trend analysis. This trend analysis gives us information about the inception of faults, which means, it predicts the fault & ends at the prediction of fault.

There are many misconceptions about condition monitoring. One of them is, Condition monitoring is done by vibration analysis or ‘only Vibration Analysis is a tool of condition monitoring’ and it is far from the truth.

1. Vibration Analysis is the “only” tool of CM is a misconception

 First of all Vibration analysis is not at all the only tool of CM (except Gear Boxes). Vibration Analysis is a prime & important tool of Root Cause Analysis (RCA). Vibration measurement (VM) is the tool of condition monitoring & not vibration analysis (VA).

 For example, the best tool to monitor the condition of the bearings is Ultrasound Measurement & not Vibration Analysis. Ultrasound Measurement gives the earliest signals about failures of bearing than any other parameter (Vibration) & Vibration is the most difficult tool to monitor bearings.

 Please see our blog explaining why Vibration Analysis is not a CM tool to get clear the concept, Misconceptions about Vibration Analysis 

2. CM is performed on the machine as a whole is a misconception.

One important thing to note here is ‘Condition Monitoring of Assets’ are deceptive words, because, actually we have to monitor the condition of components or parts of the assets & not the complete asset. It is the component or part (e.g. bearing) that fails not the asset (e.g. motor) that fails. It is the failure of a component of the asset and hence, it’s necessary to monitor the condition of failure-prone parts of the asset/machine under CM.

Therefore when we say CM of Motor, it actually means CM of Stator Winding, CM of DE/NDE Bearings, CM of Rotor Winding, CM of Shaft and CM of Installation / Alignment of Motor etc. It is the component that fails not the complete machine or all component of the machine.

Now as the failure reasons of different components are many and not always Vibration. If one has to monitor the condition of the Stator winding of the Motor then monitoring vibration is of no use. Here one has to monitor the Current in the Winding, Voltage to Winding & importantly Temperature of winding. So it’s not the ASSET or the Equipment that goes under CM, it’s the components or parts of the equipment that goes under CM.

3. Condition Monitoring means Trend Analysis is a misconception.

Now the most important point about Condition monitoring is that CM is basically TREND ANALYSIS. The absence of trend analysis, can’t be called Condition Monitoring. Trend Analysis is an integral part of CM, rather than the report of the CM. One can’t conclude or predict probable fault in absence of Trend Analysis.

Condition Monitoring is the comparison of the latest readings of parameters (like Vibration, Temperature, Ultrasound, Oil Condition, Pressure, Current etc.) with older readings of these parameters captured from the same testing instrument with the same sensor from the same part of the machine under CM.

The absence of Trend Analysis in reports means there is no periodic monitoring of the condition of a component of an asset. It might as well be called Condition Assessment

4. Condition Monitoring is done with a single tool like Vibration or Temperature is a misconception.

When I read, someone conducting Condition Monitoring of Motor or Pump or Gearbox only with Vibration Analysis, I smile. One cannot just monitor only the vibration at motor bearings and maintain the condition of any equipment (say motor).

In reality, it requires a combination of different tools for condition monitoring of different assets in industries. The different Tools/Testing of condition monitoring are Vibration Measurement, Thermography, Ultrasound Analysis, Oil Analysis, Pressure Measurement, Current Measurement, & NDT methods like Ultrasonic Thickness Testing, Eddy Current Testing, Acoustic emission testing, Liquid Penetration Testing, etc and offline Electrical Motor Testings like High Voltage Testings, Tan Delta & Capacitance Testing, Motor Current Signature Analysis (MCSA- It can be online too), Polarization Index Test, Partial Discharge Testing etc.

5. CM can be conducted wherever and however possible is a misconception.

In every instant of data collection for Condition Monitoring of any component of any asset, the same sensor should be used of the same instrument/analyzer at every instant. Also, the placing of the contact type of sensor should be at the same location/place on the component of the asset during every instant of data collection. In the case of the non-contact type of sensors, the distance from the object, the angle with the object and the direction should be the same every instant to get correct data for trend analysis.

6. Condition Monitoring is not Condition Assessment is a misconception.

Condition Monitoring is not done to check whether the parameters of components of an asset are within the limit or not. The main function of condition monitoring is to predict the failures at a much earlier stage & not on the verge of failure. The horizontal trend confirms the healthy condition of the component of the asset.  Generally, the increasing trend is being observed in this CM trend analysis. The moment trend starts increasing it should be under close watch. An alarm level is set in the trend analysis at a much lesser level than the limit of that parameter. When the actual reading reaches that alarm level, RCSA (Root Cause Symptom Analysis) is carried out to find the exact cause of why the parameter is rising. The preventive actions & corrective actions are then suggested to set back the asset in healthy conditions.

7. Condition Monitoring is Predictive Maintenance is a misconception.

We know the meaning of the word MONITORING & monitoring means observing the parameters and doesn’t mean maintenance. Condition Monitoring is understood as Condition Based Maintenance or Predictive maintenance, which is wrong. Although Condition Monitoring predicts the faults at an early stage, it’s not predictive maintenance. It’s one of the stages of Predictive Maintenance or Condition Based Maintenance.

Condition Monitoring doesn’t give any information about the root cause of the fault detected at an early stage. It only gives information about the fault at an early stage. To learn about the root cause, RCA should be done.

Frequency of CM Data Collections  

The frequency of CM data collection is depending upon the level of the parameter in trend analysis (like Ultrasound, Temperature, Vibration etc.). If the level is horizontal (flat) then there is no need to check it more than quarterly a year.

For example, consider a piece of equipment (say motor) for which the vibration limit is say 2.8 mm/sec. The vibration reading is showing 1.3 mm/sec, which is well within the limit. It remains around 1.3 mm/sec in the next few consecutive instants of data collection then the equipment is considered to be healthy. But if the vibration starts increasing, from 1.3 mm/sec to 1.35 mm/sec in next and 1.42 mm/sec, 1.48 mm/sec in next consecutive data collection instants. Then although the reading is not crossing the limit, the condition of the component of the asset will be considered as at the alarm stage. The RCSA is done to find out the exact cause of why the parameter is showing an increasing trend and then after taking corrective action the parameter is maintained back at original readings of 1.3 mm/sec or lesser.

Data collection at Fixed Intervals

Data Collection at fixed intervals like quarterly or half-yearly, may not serve the purpose of Condition Monitoring. It is because if the fault gets introduced shortly after the data collection event, then the condition of the component may get worse before the next data collection event & we may not get indications in prior.

For Example – Let us consider an example of quarterly data collection of a pump-motor. The data is collected on 1^st January and the next schedule of data collection will be on 1^st April. After 20 day’s of 1^st data collection, consider a fault got introduced in the pump-motor unit. Then, it is possible that the machine may fail before noticing the introduction of fault. I mean, before the next data collection on 1^st April. In such cases, although Condition Monitoring is in place, it is of no use.

Hence, Condition Monitoring is Monitoring the Condition of different COMPONENT of Assets periodically by using a combination of different CM techniques & finally expressed by a Trend Analysis.

Conclusion:

1. Condition Monitoring is always a Trend Analysis. (Periodic Condition Assessment is different that Condition Monitoring)
2. Condition Monitoring is done on different Components/Parts of Machines/Assets.
3. Condition Monitoring is done by using a combination of different CM techniques. And not with just a single technique.
4. Condition Monitoring is done periodically with the same instrument, with the same sensor, pointed/placed with the same angle, placed at the same place on the component of the asset under CM.
5. Vibration Analysis is not a better tool for easy Condition Monitoring.
6. CM is done only on healthy assets in order to predict the failure at a much earlier stage.
7. The frequency of CM data collection visits is depending on the condition of the component of an asset, i.e. the slope of the trend.
8. CM Data Collection intervals shouldn’t be fixed. These data collection intervals should be based on the condition of components of assets, i.e., for components having symptoms should be monitored more frequently.