Condition Monitoring Implementation basics

What is condition monitoring?

Simplest definition of Condition Monitoring, if you do a bit of web search, is given on Wikipedia’s page on the topic and its pretty straight forward. That’s why it is being produced below:

‘Condition monitoring (or, colloquially, CM) is the process of monitoring a parameter of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintenance. The use of condition monitoring allows maintenance to be scheduled, or other actions to be taken to prevent failure and avoid its consequences. Condition monitoring has a unique benefit in that conditions that would shorten normal lifespan can be addressed before they develop into a major failure.’

Periodic / Portable versus Continuous Monitoring

Condition monitoring in its simplest form could be measuring any condition parameter periodically using a portable tool or a complete system gathering and analyzing data online. 

Some of the portable condition monitoring tools which should be part of any condition assessment part are:

1. Oil Analysis

2. Vibration

3. Temperature using simple gun or thermography

4. Ultrasound Analysis

5. Motor Current Signature Analysis

6. Partial Discharge Surveys

7. Power Quality 

8. NDT e.g., Thickness measurement

And in a full blown online system, we can have some of these:

1. Online Rotating Machine Condition monitoring System consisting of various sensors like accelerometers, proximeters, key phasors, temperature sensors, shaft currents and voltages.

2. Generators and Motors monitoring system containing sensors for Partial Discharge measurement, HFCTs, Core Monitors, Air Gap sensors, Flux probes as well as end winding vibration.

3. Power System monitoring consisting of frequency, voltage, current & power transducers along with status signals from breakers, contactors, and equipment.

4. Transformer monitoring consisting of Bushing Tan delta, Partial Discharge, Moisture in Oil, Gas analyzers, temperature and tap changer position with motor currents, etc.

5. UHF sensors for online monitoring of Gas Insulated Substations (GIS) for detecting partial discharges.

And the list goes on.

Reason for CM Implementation

When all machine parameters are within the defined limits, machine’s lifetime will be as expected. As various factors influence machine operations, accelerated aging occurs, which may significantly reduce the overall usage period. So that’s the time when defect starts to set it. We still have got sometime before the functional or complete failure occurs. That’s the period where a well thought-out condition monitoring program would help prevent the failure. Suitable repair, replacement or refurbishment can restore the condition of the machine to bring it again in the defect free zone, thereby extending its life.

Knowing when to intervene is crucial for every process optimization. After years of normal running, machines reach an age when failure probability rapidly increases.

Without knowing the reasons for the machine deterioration, the whole plant process can be jeopardized. Timely optimized intervention thus helps to prevent the worse.

The reasons for the implementation of a monitoring system could be:

• High cost of spare parts inventory 
• If the inventory is not available, the parts need to be obtained from suppliers on urgent basis
• Additional staff is required to carry through maintenance and repairing

 Goal of a Monitoring System

The ultimate goal of each monitoring system is safeguarding the investment done in procuring, operating/maintaining the asset and reducing the production downtime. By controlling the most important machine aspects through its entire life cycle, it is possible to maximize the utilization of a plant, thus increasing and prolonging the return on investment.

Monitoring fault progress

It is a misconception that machine protection system installed on each critical piece of equipment would help avoid a fault to set in. No that’s not the purpose of a protection system. As the name implies, protection system would act once the fault is initiated. Its purpose is the avoid colossal damage to the asset being protected and safely removing it from service.

Even if a catastrophe is avoided, other problems are likely to occur - the production needs to be stopped or results in reduced capacities, expensive maintenance resources including spare parts, manhours on outsourcing are spent on machine repairing and large amounts of money is definitely lost.

The major benefit provided by a machine condition monitoring system is complete overview of all the key phases in the machine lifecycle - normal state, occurence of fault and eventual failure. Being able to react in the first two phases is critical in order to eliminate the failure phase and lost of value. Monitoring systems in the world have developed to a stage that failure can be predicted days or week in advance. These online systems however have to be correctly selected and implemented for the type and service of your machinery.

When to consider a CM system?

The biggest reason for introducing a monitoring system is that money lost as a result of machine failure costs much more than the machine itself. The associated costs have been discussed above.

Condition monitoring can foresee a failure before it turns into catastrophy.

The organization should carefully evaluate important aspects of its production plant and make an informed decision regarding the implementation of a CM system. Ideally CM is implemented as a part of a new greenfield project. However, it  can be easily introduced at a much later stage in the existing facility during upgradation, capacity enhancement, refurbishment or in the regular maintenance. Especially when your equipment is safety critical or business critical a monitoring system should be installed.

Factors to consider in CM Implementation?

• Equipment criticality - the equipment importance for the business and/or safety
• Cost benefit analysis - an installation of a monitoring system can reduce the cost of regular maintenance or reduce the maintenance frequency and hence result in savings. So ROI – return on investment calculations should be carried out.
• Inventory availability or longer lead times - a machine or its spare parts may not be always available, or are simply too expensive or lead times are too much and breakdown cannot be afforded.
• Downtime for implementation - installation of a CM systems without disrupting production or reducing it. As described above, it can be done during a shutdown or refurbishments if planned well ahead of time.
• Operating conditions - the environment of a machine is harsh and may directly influence the machine lifetime
• Poor Equipment condition - the machine itself is old or in bad condition, which indicates that catastrophic failures may occur in future.
• Installation possibilities - the machine allows for sensors and monitoring apparatus to be installed. And this important. Some modification may be necessary to install the sensors in the casings, or inside the equipment. Has to be considered well in advance with a Risk Analysis as well.
• Fault frequency - faults occur frequently and reasons need to be investigated to prevent future malfunctions. Condition Monitoring in this case will help reaching to the true cause of repeated failures.