The technologies for monitoring your machine condition has been evolving and advancing at a tremendous rate and they will continue to evolve for decades to come. However, for a vast majority of equipment, there are no inspection technologies better then a human being. The basic form of inspection has been carried out forever; but we are here with inspection practices that challenge the conventional methods and bring about additional clarity in your maintenance program. As opposed to conventional methods, you don’t simply “look” at the seal, bearing, pump or coupling. You “examine” all these components carefully and purposefully. You extract information that the machine is presenting to you in the form of signs. Inspection of this kind requires linguistic skills so as to effectively translate signs from the machine into corrective actions. These new inspection practices are designed keeping in mind that the condition monitoring potential of a trained human is much greater than that of an instrument.
The nature of inspections
Simple solutions are usually the best solutions; hence we recommend inspection routines that achieve optimum level of reliability after minimizing complexities. These inspection practices are much better than other condition monitoring options as evident from the following facts.
- The measures and practices deployed are simple and inexpensive.
- The emphasis is on “total productive maintenance” and is carried out by an operator.
- Relies mostly on Examination skills rather than technology.
- Based on root cause analysis to avoid recurring faults.
- The approach is predictive and proactive, rather than reactive.
Analysis should be performed every day, on almost all machines. This may sound expensive, but it’s actually not. You can do oil analysis with your senses through inspection windows. Oil analysis doesn’t necessarily require laboratory testing. An example of inspection windows is the sight glass that enables you to examine the oil every time you walk by your equipment. Bringing vision to critical zones within the machine will help you assess the condition of your machine with great efficiency and frequency. Another convenient inspection apparatus is the bottom sediment and water bowl. The BS&W bowl shows any contaminant in the oil that is heavier than oil, when properly positioned with good light. Contaminants like sediment, wear, water, sludge, coolant, debris, dirt and dead additives can easily be discovered and removed from the oil before they do any damage.
Potential-to-functional failure interval
An important concept to understand, for performing Reliability-Centered Maintenance is the potential-to-functional failure interval. Commonly known as P-F interval, it is the amount of time between detecting a potential symptom of a failure (Or a warning) and an actual functional failure. It’s a theoretical concept with useful applications, but it is rarely used in real world machines. The reason is that the real world machines have too many variables. These variable events hamper the predictability of P-F interval. These variables are:
- Other Components inside the machine with their own P-F tendencies
- Other failure modes for the same component
- Varying work cycle (loads, temperature, shock, speeds)
- The P-F interval reduces as the machine ages.
- Methods for detecting failure and effectiveness vary.
Looking at the given points, we can clearly derive that measuring P-F intervels is unreliable; and to remedy that we should increase frequency, as discussed earlier. Using imbedded sensors for certain high-speed and high-risk machines is justified but for all other machines, inspections should be carried out by using inspection windows.
Root Cause Analysis
Your machine’s P-F interval is extremely difficult to predict due to all the variables involved and it can vary from seconds to decades. This makes it very difficult for maintenance professional to schedule needed corrections. The best strategy to overcome this problem and avoid catastrophic failures is to focus on root-cause analysis. It is a proactive maintenance strategy that deals with fault bubbles before they escalate into an active failure event. Stopping a failure at inception should be given equal importance as identifying the failure in progress. Your inspection strategy should identify all root causes of potential failures. There are always one or more root causes of any failure mode.
Following are a few cases that require root cause analysis to identify and neutralize the threatening condition in your machine:
- Ruptured oil filter
- Severely degraded or wrong oil
- Mobilized or disturbed bottom sediment (Fish-bowl conditions)
- Severe shaft misalignment
- Slit/stiction lock in hydraulic valve
- Grease starvation of an autolube system (soap lock)
- Stopped oil supply to a splashed-lubed gearbox
- Heavy fuel dilution in a diesel generator
- Compressor oil heavily contaminated by chemicals
- Seawater contamination in a shipboard hydraulic fluid
The new way of inspection is mostly about execution. Inspection is a repetitive and mundane task; by reinventing it we are making it 10 times more effective with just a minor increment in total cost.
This information is provided for guidance and informational purposes only. This website and information are not intended to provide investment, laboratory or manufacturing process advice. The information contained herein has been compiled from sources deemed reliable and it is accurate to the best of our knowledge and belief. However, Castrol cannot guarantee its accuracy, completeness, and validity and cannot be held liable for any errors or omissions, as the results change depending on the working condition/environment. Changes are periodically made to this information and may be made at any time. All information contained herein should be independently verified and confirmed.