Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/490438
22 March - April 2015 | www.machinerylubrication.com only causes water damage to the lubricant but also abrasive damage to the equipment. In many cases, water contamination can be identified onsite with a visual test, as emulsified water in oil will become milky. However, air entrainment is another potential issue with cloudy oil, so you should go beyond just a visual test. The hot-plate crackle test can also be used to check for water onsite as well as at most commercial laboratories. You can perform a go/no-go test by simply raising the hot-plate tempera- ture to 320 degrees F and seeing if the sample sizzles like bacon when you put it on the surface. Of course, this should be done with caution, since hot liquid can spatter if there is a lot of water. Other methods are also available, but the hot plate provides a good initial detection for general-purpose analysis. For a more exact measurement or to detect water at very low levels, have a Karl Fischer water test done. There are multiple variations of this test, including coulo- metric and volumetric, but they all have similar capabilities. Check to see which is being performed and if it will meet your needs. Coulometric tends to be more accu- rate at lower levels, while volumetric is usually better at higher levels. Certain additives, such as those that contain sulfur, can interfere with this type of test and should be taken into account. Typical oil analysis recommendations include correcting the source of water. This should be done before any further action is taken. In some applications, water must be removed continu- ally, and the water ingression cannot be prevented. The next most common recommendation is to change the lubricant. This may be suggested in conjunction with other water-removal options (water drain-off, dehydration, centri- fuge, etc.), depending on the lab's knowledge of the sump size and the site's capabilities. Incorrect Lubricant Incorrect lubricant problems come in a myriad of forms. The most common include using a mineral oil in a glycol-based lubricant sump, missing additives/wrong additives and the wrong viscosity. With a mineral oil in a glycol-based sump, you tend to see increased viscosity and sludge formation due to the chemical reac- tion between the hydrocarbon and glycol products. Once this chemical reaction begins, you may notice excessive wear, as the lubricant viscosity is excessively high. Since the two lubricants do not typically mix, you may also observe elevated wear because the load-zone lubricant film will not be a single lubricant and could have a reduced load-carrying capability. Significantly reduced lubri- cant life is also likely to result. Because of the increased viscosity and sludge formation, you may have slow-flowing or even plugged filters. Acid formation as a degradation byproduct can also increase and attack the lubri- cated surfaces. Viscosity testing and metals analysis are the primary methods used to identify a mineral oil in a glycol-based sump. Information about the lubricant in use will be required by the analyst to properly interpret the results. If a mineral/glycol contamination issue is discovered, the likely recommendation would be to flush the sump. There is no other filtration option for a lubricant contaminated in this manner, so the contamination must be physically removed. Another recommendation might be to review the relubrication practices, since this type of contamination usually is the result of OIL ANALySIS Water contamination can often be identified with a visual test. The hot-plate crackle test can also be used to check for water contamination.