Jarrod Potteiger is senior technical consultant and manager of Training Services for Des-Case Corporation, Goodlettsville (Nashville), Tenn. Prior to joining Des-Case, Potteiger was a director of services for Noria Corporation, where he helped educate clients on the benefits of precision lubrication. He has published a variety of technical articles on condition monitoring, contamination control, bearing lubrication and lubricant consolidation. He holds a Bachelor of Science degree in chemical engineering from the University of South Alabama and is a certified maintenance and reliability professional from Society for Maintenance and Reliability Professionals.
Breather plugs are easily replaced with inexpensive breathers that efficiently filter particles as small as two microns and absorb moisture down to approximately 20 percent relative humidity. This method of controlling contamination is often referred to as head space management and usually requires simple modifications to effectively execute.
The final contamination control is seal quality. The use of inexpensive seals often leads to oil leaks and the ingression of contamination. Using high quality mechanical seals will prevent the vast majority of these problems when properly installed. If process fluid migrates down the shaft from the pump to the bearing housing, consider using a collar on the shaft to deflect the fluid. When gross moisture contamination is likely, a bottom, sediment and water (BS&W) bowl provides an effective way to inspect for free water and drain it with the included drain valve.
BS&W bowls provide an effective way to inspect for and remove gross water contamination.
Some maintenance personnel may argue that routine visual inspections are the most important type of PM. However, the most significant problems associated with the lubrication of these systems cannot typically be observed without instrumentation.
Oil analysis is unique in its ability to serve as a proactive condition monitoring tool. Rather than simply focusing on the symptoms of problems and serving as an early warning for bearing failures, oil analysis is ideal for proactive condition monitoring to detect the root causes of machine failure, so they can be eliminated. The most common root causes of wear, and ultimately failure, in oil lubricated bearings is particle contamination, moisture contamination or using the wrong oil or one that has degraded beyond the point of usefulness.
Oil analysis is perfect for identifying and quantifying all these conditions. Using viscosity testing, acid number, fourier transform infrared (FTIR) and elemental analysis, end users can determine if the correct oil is in the machine and determine its fitness for use.
Particle counters, when used correctly, can indicate the exact level of particle contamination in many size ranges. Certain moisture tests can give an accurate measure of moisture contamination. Detecting and eliminating these problems dramatically extends the life and increases the availability of these assets.
In addition to proactive functions, oil analysis can be a sensitive tool for identifying bearing faults far in advance of a failure. Unfortunately, many users of oil analysis are not aware of these benefits for a number of reasons, but the most prevalent is poor sampling methods.
Some of the most important tests require good sampling practices to provide any real value. Sampling from drain ports typically yields poor results and can lead to unnecessary corrective action. To take a representative sample, machines should be sampled while in operation, and for most pumps, this method leads to a dangerous drop in the oil level. Traditionally, those who attempted to take “good” oil samples used the drop-tube method, which requires the insertion of a flexible tube into the oil sump. This method is cumbersome and can also provide poor results.
The biggest problem is the inconsistent location of the sample extraction point and the likelihood of contaminating the tubing. To take high-quality, repeatable samples, proper sampling hardware should be installed. The proper type of hardware for most pumps is a minimess-style sample valve with a pitot tube. The minimess is a normally closed check valve—similar to a hydraulic diagnostic valve—that requires an adapter to open it.
For wet sump applications, such as pumps, these devices are available with a pitot tube that can be cut to length and bent to facilitate sample extraction from the desired location. Because most pumps have numerous drain or side ports, these devices can be easily installed. When used properly, the devices provide highly repeatable and valid sample data. They also make sampling easier, safer and more efficient than other sampling methods.
Proper sample valves provide consistent valid data and make sampling easier.
Design for Precision Lubrication
Precision lubrication is difficult for the average pump given the typical configuration. However, with minor modifications it can be relatively simple. A myriad of inexpensive devices are available for inspection, contamination control, lubricant application and oil sampling. Most of these devices can be easily installed.
The most efficient way to incorporate these items is to specify them during the design and installation phase, but retrofits in the field are usually easy as well. Precision lubrication requires using the right oil, in the right place, in the right amount, at the right frequency, in the right condition and with proper equipment design. P&S