Oil analysis is similar to visiting your doctor for an annual blood test. The doctor can determine your overall health and well-being from a very small sample of your blood. The same can be done with oil-lubricated equipment such as engines, gear-boxes, hydraulics, air compressors, and turbines. It has been estimated that many maintenance technicians change the oil too early or too late. Changing oil too early wastes money on oil, filters, and labor. Changing oil too late can lead to deposit build-up and costly equipment repairs. The best way to determine when to accurately change oil is through oil analysis.
When taking an oil sample, the system should have been running for at least 30 minutes. This will heat the oil and also allow for an equal distribution of wear metals and contaminants. The system should be turned off before a sample is drawn. The oil sample should feel warm.
The following are the seven steps for proper oil sampling using a hand pump.
1. Cut a length of ¼-inch poly tubing approximately six inches longer than the oil dipstick or long enough to reach near the bottom of the sump. Always cut the tubing at an angle.
2. Loosen the knurled knob on the hand pump and insert the tubing through the hole in the knob until the tubing extends about one inch into the sample bottle. Tighten the knob so that the “O” ring seats tightly around the tubing.
3. Remove the cap from the sample bottle and screw the bottle onto the hand pump, making sure the bottle is seated properly.
4. Insert the tubing into the dipstick tube, making sure it extends into the crankcase or reservoir.
5. Pull out the plunger on the pump one time only; wait for the bottle to fill. If everything is tight, the bottle should fill within seconds. You may have to pump it several times in order to create a vacuum.
6. When the bottle is full, release the vacuum that has been created by unscrewing the sample bottle or opening the rubber cover in front of the hand pump. The rubber cover seals the sampling valve. Pull the tubing from the dipstick or reservoir, remove the bottle from the pump, cap the bottle, and put it in the shipping container.
7. Carefully and completely fill out the sample identification form and send it to the lab and discard the tubing; never re-use it.
In certain instances, the only way to obtain an oil sample is by taking it while the oil is being drained from the sump or the oil pan. In this case, sample by:
• assuring that the sample is warm from a system that has been running for at least 30 minutes;
• wiping the surrounding area clean to reduce cross-contamination;
• draining at least a quart of oil before passing the sample bottle into the stream of oil. The oil will be hot so wear the appropriate protection or use a pair of pliers to hold the sample bottle under the oil stream.
Then carefully and completely fill out the sample information form, place it in a shipping container, and mail the sample to the lab.
An oil sample should be taken just before the regularly scheduled oil change. If the oil analysis results indicate that the oil is in good shape, extend out the change interval by 30 percent. It is recommended to test the oil again prior to the extended change-out. In certain cases, it may be difficult or impractical to sample every system. If this is the case, it is recommended that sampling be done as follows:
• Critical systems – These systems or equipment are responsible for production. If a component on a critical system fails, production is halted. The critical systems are the ones that have been identified as being essential for continuous operation. These systems may require quarterly or semi-annual sampling.
• Sample population of representative systems – The sampling of less critical systems may not be necessary but would still improve plant reliability. Say, for example, a plant has 48 gearboxes that run machines that are essential but not critical. The 48 gearboxes are essentially all the same make, model, and year and have the same operating conditions. Oil samples can be taken on 10 percent of the total and still provide information that could be transferred. Note that every system has unique operating conditions. Sweeping generalizations should be avoided.
An effective oil analysis program increases the reliability and availability of equipment while reducing the costs associated with labor, repairs, and downtime. The oil analysis process consists of properly taking the oil sample, sending it into the laboratory for analysis with accurate information, and receiving the results in a timely manner and in a concise format.
Without the proper controls in place prior to analysis, testing may be performed on non-representative, mislabeled, or outdated samples, which in turn will lead to the wrong corrective actions and added costs on the oil analysis program. If these issues of control are not considered prior to the sample arriving at the laboratory, any test results obtained will be of small value.
There are also control issues to consider once the analysis has been performed and the results have been obtained. Things to consider when setting up an oil analysis program:
• establish baseline test of new lubricants;
• use proper sample labeling procedures;
• select applicable test methods (pump or valve);
• set timely sampling, analysis, and corrective action, if needed.; and
• establish preventive maintenance schedule.
An oil analysis program can provide critical information for any piece of equipment requiring lubricants – gasoline and diesel engines, transmissions, gears, bearings, air compressors, turbines, generators, and hydraulic systems. It is also useful for owners of passenger cars, over-the-road fleets, off-highway equipment, boats, or high performance vehicles. Oil analysis has been able to identify problem areas before they become catastrophes and dramatically extends out oil change intervals.
Getting Down on the Floor - April 2006 Render