Condition-based Maintenance: Tools to Prevent Equipment Failures

Rendela Wenzel, Eli Lilly and Company
Tags: oil analysis, maintenance and reliability

One of the crucial roles of a reliability engineer is to develop and maintain a long-lasting and effective predictive and preventive maintenance program. The main expectations of this type of program are that a company can reduce unscheduled downtime, increase production and improve overall equipment reliability.

It is essential to understand how the equipment performs in a facility and to be able to predict and prevent failures before they happen. The results of the combination of these technologies will give the reliability engineer an even greater confidence when communicating to management when an asset is approaching an impending failure.

This article provides an overview of the utilization of oil, vibration and thermographic analysis in combination with one another to prevent equipment failures. This type of approach, referred to as the “two-out-of-three technology rule,” will give the reliability engineer greater confidence when asking to take an asset out of production to do the necessary maintenance.

Payback Technologies and How They Relate to One Another

There are generally three accepted technologies that are looked upon as the main “payback” technologies. They are oil analysis, vibration analysis and infrared thermography. These technologies are essential in order for a reliability engineer to maintain an accurate “condition assessment.”

A comprehensive and well-designed condition-monitoring program will incorporate different aspects of existing technologies to improve equipment performance, decrease the number of equipment failures and reduce the risk of equipment downtime.

Payback Technologies and the Problems They Detect

Vibration analysis looks at rotating through various waveform trends and pattern recognition. The types of faults that you look for in vibration spectra to correlate with various technologies are as follows:

Oil analysis examines fluid properties, contaminants and various kinds of wear debris to determine machine health. Each aspect of oil analysis can help correlate machine issues well before any other technology. Oil analysis is comparable to a blood test on the human body. It has been said that more than 70 percent of failures are lubricant related.

One of the benefits of oil analysis is that it detects problems in both the fluid and the machine. It can also detect some defects earlier than other technologies. Oil analysis is often referred to as the first line of defense as far as predictive technologies are concerned. The oil sample reports will define the following items:

Strengths and weaknesses of vibration analysis coupled with oil analysis
Strengths and weaknesses of vibration analysis coupled with oil analysis

Correlation of lubricant wear and wear particle analysis with vibration and thermography
Correlation of lubricant wear and wear particle analysis with vibration and thermography

Thermography detects heat patterns and measures temperatures of electrical and mechanical components. It can identify a temperature difference or “hot spot” due to electrical resistance or excess friction. Thermography can be used in a number of applications to understand problems with moisture, thickness, bonding, capacitance and friction.

It can also detect problems via heat loss from mechanical equipment. Most infrared imaging thermography is qualitative. The types of anomalies that you look for in correlating data with other technologies are:

The Bomb Report

The bomb report was developed out of necessity as a way to get management to understand the severity of what the reliability program was trying to tell them. When so much money has been invested in technology, training, additional manpower, etc., you need to provide a means of tracking and presenting your successes to sustain any reliability program.

The bomb report is essentially an executive summary on the asset in question. It has the following attributes:

This simple name for the report holds great connotation when verbalized in any operational meeting. When I present this report as a bomb report, managers tend to listen. I have that hard-to-get 10 to 12 seconds of management’s attention to really drive home the fact that we have a problem out there on the floor and need to react quickly to avert disaster.

So many times reliability engineers will make a call with only one bad oil report in their hands and realize that they called for something to be done to a machine that had many more months, if not years, of life left in it. They make a decision on a bearing because they may have seen a slight spike in lead, tin or aluminum.

They could have made a call on a gearbox when they saw a slight increase in iron. Without having the benefit of two or even three technologies telling you the same thing, you do not have the confidence to honestly ask for production to remove an asset from service for maintenance.

Making calls on machinery is a risky business. After all, a million “at-a-boys” with one slip-up will cost you years of personal credibility. Without having the benefit of multiple technologies coming to the same conclusions, you run the risk of losing not only your credibility but also your job.

A reliability engineer needs to be trained in various technologies to understand and appreciate the benefits and limitations that each one displays. Oil and vibration analysis are excellent in combination with one another, and vibration analysis and thermography are good complements.

It depends on the situation that presents itself to know which technologies to utilize to get you the answers that you need and in the most conclusive way possible.

Two-out-of-three Technology Rule

There are a few rules of thumb I use in looking at my condition-monitoring program holistically. By following these few simple thought patterns, a reliability engineer will have the best arsenal at his disposal to solve any equipment-related problem that is presented to him.

Correlating more than one technology has huge benefits for being able to accurately diagnose problems and rectify them before they become production outages. A reliability engineer has at his disposal many tools in the industry to be able to predict and prevent these types of equipment issues from happening and also to avoid recurrence.

If a few simple steps are followed, such as the two-out-of-three technology rule, a reliability engineer can be extremely confident in the decisions to rebuild, replace and perform specific maintenance on equipment.

Main Urea Pump Bearing – Vibration Data (Spectrum)
Main Urea Pump Bearing – Vibration Data (Spectrum)

Main Urea Pump Bearing – Vibration Data (Waveform)
Main Urea Pump Bearing – Vibration Data (Waveform)

Main Urea Pump Bearing – Oil Data
Main Urea Pump Bearing – Oil Data