Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/258778
4 | January - February 2014 | www.machinerylubrication.com As I see It • Stratified solids (dense zones of soft contami- nants, oxides and dead additives) • Sediment (settled hard contaminants like dirt and wear debris) • Water and other settled liquid contaminants (e.g., antifreeze) Often the sludge and sediment found on the bottom of sumps and reservoirs are tightly bound by water. Most oil impurities are polar (water loving) in nature. When free and emulsified water contaminates an oil, this water can act as a mob to collect and bind together these impurities. Eventu- ally, the growing sludgy mass is pulled by gravity to the sump floor. Dirt and wear debris that fell by normal sedimentation can also cling to these sludge pools. Early Detection of BS&W is Key As mentioned previously, BS&W is symptomatic of a host of problems and issues related to your oil and machine. Failed and degraded oil, environmental contam- inants (e.g., dirt and water), active machine wear and corrosion all produce BS&W. It is important to know if BS&W is present so you can start the troubleshooting process and find the originating cause. This can be accomplished by 1) using BS&W bowls, 2) periodically taking drain port samples or 3) using a drop-tube vacuum sampler in which the tube is lowered to the bottom of the sump. The seriousness of BS&W goes far beyond machine problems that produce sediment and water. BS&W can lead directly to sudden-death machine failure. For instance, disturbing the sediment in oil lubrication systems can produce what is called the "fishbowl effect." Those who have had tropical fish know that the slightest agitation of an unchanged fish bowl causes the water to become murky with sediment, uneaten food and excrement. In the same sense that you wouldn't want a loaded oil filter to burst, sending a dense debris field downstream, you also wouldn't want to agitate the BS&W in your sumps and reservoirs. Imagine this sequence of events relating to an oil change: 1. The drain port of a reservoir is removed, and the aged oil flows out by gravity into a waste oil container. 2. Some of the BS&W is purged with the oil, but much of it stays clinging to the reservoir floor. 3. During the drain, oil flowed by gravity toward the tank through piping, valves, pumps and filter housings, carrying suspended particles that were previously trapped in nooks and crannies. Some of these backwashed parti- cles resettle in various locations, presenting the risk that they will be re-entrained into the oil when the machine is restarted. 4. When fresh new oil comes plunging into the reservoir, the BS&W is stirred up into a murky mass. In an ideal world, you wouldn't allow bottom sediment and water (BS&W) to accumulate, and oil changes wouldn't be necessary. However, nobody lives in an ideal world. While you can't eradicate BS&W in the real world, you can control its accumulation and resuspension by employing the following suggestions: • Use a BS&W bowl to monitor and periodically time the purge of BS&W "on condition." This will prevent hazardous accumu- lations and help track the source and rate of generation. • After a needed oil drain, use a discharge wand from a filter cart to rinse out remaining BS&W from tank and sump bottoms before refilling with new fluid. Confirm that the rinse was successful by inspection. • After new oil has been added, circulate the fluid through a filter at the highest flow rate possible before the machine is started and put under load. Use a filter cart, if necessary. Allow the total oil volume to turn over no less than five times. Do a simple patch test or particle count to confirm cleanliness, especially for critical equipment. How to Prevent the Fishbowl Effect