You have your equipment, everything is set up and ready to run, but what about your lubricants? Too often, lubricants receive little attention with respect to their use in rotating equipment. Even the most reliable cars in the world will encounter problems on a short commute if the wrong transmission fluid is used during a flush. The same is true with your Positive Displacement (PD) blower or vacuum booster that operates around the clock. In our experience, approximately 80% of all bearing and gear failures are the result of improper lubrication.
Shown is an example of gear failure from improper lubrication.
PD rotary lobe blower and vacuum booster oil should be considered as important as any of the machine’s other primary components. It is absolutely essential for smooth, efficient machine operation, and the correct oil will easily pay for itself in savings and convenience.
In this two-part article series, we review the purpose of blower and vacuum booster lubrication. We also discuss oil specifications, exploring what they mean and offering insights for selecting the most beneficial oil.
More to Lubricant than Meets the Eye
For now and the foreseeable future, bearings, gears and oil lubrication are at the heart of rotating equipment. But is correct oil specification really that critical? Isn’t oil just a lubricant? It turns out, there’s much more to the story.
Of course, the most evident function of oil is to provide lubrication at the interfaces between sliding surfaces. By introducing a thin film between moving components, such as meshing gear teeth, contact is minimized or even eliminated, and the coefficient of kinetic friction is dramatically reduced. This results in less component wear, less frictional heating, and longer asset life.
Where there is oxygen, corrosion is likely to be found. Oftentimes, copper and iron surfaces act as catalysts for corrosion at temperatures above 200°F, accelerating the corrosion process further. The key is to prevent oxygen and water from contacting corrosion-prone components with a film of oil containing the right barrier-forming additives. When oil is specified incorrectly, components may not be protected properly during or between operation cycles, exposing components to corrosive damage.
Cooling is another crucial function of oil. Most of the heat generated by a positive displacement rotary lobe blower is the result of gas compression as it exits the discharge into a high-pressure region. Some of this heat is carried away with the gas as it is pumped, while some of it is transferred into the blower housing, ports, and end plates via conduction. Since oil can transport heat five to 10 times more effectively than air, the blower oil sumps are able to move just a small amount of this heat from the end plate to the inside surfaces of the oil covers, and eventually into the ambient air by free convection using the oil as a transportation mechanism. Most importantly, the oil transfers the heat away from dynamic contacting parts, protecting them from thermal damage.
In applications where lip or mechanical face seals are used, oil also serves both as a lubricant and sealant between rotating and stationary parts of the seal. As the oil is drawn into the space between the seal rotor and stator by a combination of the capillary action and drag, it augments the seal’s ability to do its job without blistering or cracking. Without proper lubrication, seals quickly fail due to the extreme temperature that develops where the rotor and stator meet.
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