Importance of lubrication
Despite the fact that correct lubrication is one of the most crucial aspects of a reliability program for rotating equipment, lubrication is often perceived as a low level job that doesn’t require much experience or skill. Lubrication-related failures are probably the most preventable type of all failures of rotating machinery, yet it’s an area of industry that isn’t always allocated the appropriate level of attention. Lubrication helps in:
Reducing wear of moving parts
Reducing friction between rotating parts and stationery ones
Reducing operating temperatures
Minimising corrosion of metal surfaces
Keeping contaminants out of the system
Sealing and protecting components
The incorrect choice and application of lubricants is said to account for around 40 per cent of all machine failures, and so lubrication procedures are a critical factor in maximising your equipment’s reliability. Once lubrication has been applied, the equipment and the lubricant should be tested to see if:
The correct formulation of lubricant was used for the application
Whether the lubricant solved – or merely masked – the problem
Whether the amount of lubrication applied was correct
The need for frequent lubrication may well be a symptom of underlying machinery damage (such as wear or damage to bearings, shafts or seals) so the solution isn’t simply to lubricate to stop vibration or excessive noise. In fact, too much lubrication can be just as detrimental as too little lubrication. Under lubrication can cause bearings to wear out before their time, whereas over-lubrication can lead to catastrophic results to the bearings or long-term damage to motor coils and windings.
It is critical to follow the manufacturers’ recommendations and use the right type and quantities of lubricant with the appropriate frequency of application that is best suited to the machinery’s optimal functioning. An optimal lubrication program requires vigilance, skill and experience from the operator and should include thorough checking and testing procedures using quality equipment. Ultrasound technology will not only improve machine reliability and help a production line run more smoothly, the big picture is that it can help to decrease the cost of production and the cost of maintenance, enhance safety and improve quality control. The key focus should be on finding the best technology that meets organisational needs and making sure that it delivers both financial and operational benefits.
Best practice lubrication regimes will ensure world-class machinery reliability, so it’s worth talking to an experienced supplier of technical equipment to ensure your testing and inspection procedures are up to the task.
OIL ANALYSIS — THE BASICS
Much like doctors assess our health though blood analysis, critical plant equipment must be monitored in much the same manner. Chronic lubricant or equipment symptoms show up as indicators in oil analysis samples and, if left uncorrected, can lead to equipment degradation and lost productivity. Therefore, the goal of a proactive oil analysis program is to trend gradual changes in fluid properties, contaminants and wear debris so that corrective action can be initiated in a controlled, planned manner.
Oil analysis benefits include:
Optimum equipment life
Extended oil life
Oil analysis assists maintenance personnel in two primary ways:
First — Determining the physical condition and contamination of the oil. Lubricant serviceability can be impacted by either reaching the lubricant’s life span OR contamination levels have reached a point requiring a drain and refill, unless purification is an option. When talking about contaminants, the objective is to detect the presence of foreign components and to ask “What are they? Where did they come from (built-in, generated, ingressed, introduced)? How can I prevent further entry or generation?” Contaminants act as a catalyst for wear.
This generated wear debris further acts as a catalyst for additional component wear. If the cycle is not broken, wear accelerates and downgraded serviceability results.
Second — Monitoring wear metals for abnormal machinery distress conditions. Wear debris analysis relates specifically to the health of your equipment. As you know, the main function of a lubricant is to separate two surfaces, in relative motion to each other, from making contact. However, its is generally impractical to maintain a lubricant film that will keep those same surfaces totally separated from each other. Thus, metal-to-metal contact can occur, even in today’s high-tech equipment. In addition, keep in mind that boundary lubrication will always be present during start-up. At that critical point in the machine’s operation, some normal and/or abnormal wear metals will be generated, with the amount depending on equipment design and whether or not it has proper lubrication.
The following tests are used by ExxonMobil (depending on application) to determine changes in physical properties of the oil, oil contamination and equipment wear debris:
Viscosity by ASTM D 445: indicates changes in fluid’s resistance to flow. Viscosity results can indicate either physical changes or contamination by other fluids.
Oxidation by FTIR (Fourier Transform Infrared Spectrometer): identifies harmful by-products of thermal degradation. Lubrication oxidation represents a physical change.
Nitration by FTIR: identifies harmful by-products of fuel combustion. Nitration is a physical lubricant change, much like oxidation.
Glycol by FTIR/ASTM D 2982: identifies the presence of engine coolants.
Soot by FTIR: identifies the by-products of unburned fuel.
This is also contamination.
Water by FTIR/hot plate/Karl Fisher ASTM D1744: identifies the presence of water, a common and potentially harmful fluid contaminant that can accelerate physical lubricant change and rapidly degrade metal surfaces.
Total acid number (TAN) by ASTM D 664: measures/identifies acid by-products of oxidation and contamination. TAN is a physical change.
Fuel dilution by gas chromatography: identifies the presence of fuel, another contaminant.
Elemental Analysis by ICP (Inductively Coupled Plasma Spectroscopy): identifies both additive and wear debris metals.
Total base number (TBN) by ASTM 4739: identifies acid neutralising capacity. This is a physical lubricant change.
ISO particle count: identifies the size and amount of solid contaminants.
Where to start
It’s easy to see the importance of a proactive oil analysis program, but knowing where to start can often be overwhelming. Don’t let the vast array of analysis hardware and test results keep you from getting started. Here’s a simple seven-step process to get you off and running:
Step 1: Identify “mission critical” equipment: It’s not necessary to perform oil analysis on every single lubricated system in your plant. Identify critical applications that would seriously jeopardise production if they were to shut down unexpectedly.
Step 2: Register your equipment: It is important to have your equipment properly registered with the lab. This supports routine trending and plays a key role in early detection of lubricant or equipment problems. There’s no need for you to decide which tests are appropriate for a particular application because the lab has already established test slates for specific applications.
Step 3: Establish Best practice: Establish a consistent “how-to” practice for taking oil samples from your equipment and train your maintenance personnel to use this practice. Correct sampling practices are critical to the value received from the analysis data. This extremely important step rarely gets the attention it needs.
Step 4: Sample: Retrieve samples in accordance with your best practice and send them to the lab as soon as possible. Samples that are set aside may deteriorate and give non-representative results. For further guidance on Steps 3 and 4, please see Signum Oil Analysis technical information guide titled “Condition-Monitoring Fundamentals.” This guide can be found on www.signumoilanalysis.com.
Step 5: Analyse: A thorough analysis, keyed on trends, helps determine your systems’ conditions. General laboratories may have a pretty good idea of what they are measuring, but often know little about specific formulations and don’t always understand whether or not the differences they see are significant.
Step 6: Interpret: Reviewing the results and determining what, if any, action is required can make or break a successful program. ExxonMobil has an extensive database of test results and has developed recommended control limits based on years of testing. In any case, it’s important to remember that an alert sample does not necessarily mean imminent failure. Seek consultation on alert samples and re-sample to confirm present data before taking massive corrective action.
Step 7: Take corrective action and document!: As always, documentation is the key to knowing where you’ve been and where you’re going. Document corrective actions resulting from oil analysis. Historical oil analysis and corrective action documentation is difficult for an OEM to dispute when you call for warranty work.
why sampling programmes fail
When sampling programmes fail, the reason is usually one of five major factors:
Lack of understanding: Knowing what to expect from your analysis program helps determine the right units to sample and the best sampling frequencies. Before starting a sampling program, you’ll find it useful to define why you need a sample program and how the test data relates to the productivity of your equipment.
Lack of interpretation knowledge: It is important to know the equipment well enough to quickly relate the analysis results to the noted performance of the equipment being tested.
Lack of commitment: There must be a mutual commitment from all involved, from the highest levels of management down to the person taking the sample. For the program to succeed all parties must be willing to devote time and training to the program.
Poor sampling procedures and practices: Improper sampling procedures cause erroneous results.
Irregular sampling frequencies: Monitoring fluid condition and system performance by trending is far superior to hit-or-miss sampling methods. Lubrication scheduling and oil analysis software, such as Mobil Monitor LMS and Mobil Monitor Lubrication Technician can assist in the implementation and tracking of routine sampling. Oil analysis is a useful, predictive and proactive too that can help prevent equipment breakdowns, determine the root cause of failures and aid in locating operational and contamination problems. If you need help implementing an oil analysis program, our ExxonMobil field team is ready and willing to help. We can help develop your program and provide on-site technical support and training to properly administer this seven step process.
“Protecting Your Assets With Oil Analysis” By Jon Sewell, Mobil Periodical — “The Engineered Difference”
- VIKAS DAMLE