Setting Base Number Alarms

First, look for things that may cause the leak (leaks normally do not start for no reason). Leaks are often caused by pressure buildup. Look for plugged vents, overfilling and elevated heat levels. Stress from too much torque can cause gasket failures that lead to leaks. (Submitted by Craig Havener, Manager, Lafarge North America. Thanks Craig!)

From "Wear Debris Analysis"

Different systems exhibit different trends. For instance, the wear debris generated from a system involving gears and bearings may well be quite high initially, particularly if no attempt has been made to 'run-in' the system. Thus, there is a gradual reducing level of debris until the system settles in. Then comes the acceptable very low wear rate associated with well-lubricated surfaces, which perhaps increases just slightly. Finally, the machine begins to show signs of fatigue or fracture and particle generation increases at an ever increasing rate.

Lube-Trivia: The Cost of Wear

Test your knowledge and prepare for ICML lubrication and oil analysis certification.

QUESTION: It is often stated that the cost of wear is two-thirds of the cost of energy. True or false?

Q & A: Setting Base Number Alarms

"The oil we use is a 15w40 oil. What would be an acceptable base number (BN) range of measurement (high to low) to indicate the life of oil? On my oil analysis reports, do I go by the BN or do I go by where it states on the sample report for "contamination", "oil conditions", or "wear"? Would the BN range be the same for all 15w40 oils?"

BN measures detergent alkalinity (reserve) in crankcase oil. The crankcase oil will suffer a loss of alkalinity due to acid generation in the crankcase causing a drop in BN. Thermal degradation and fuel/water dilution will also cause a drop in BN.

Typical rule-of-thumb caution levels for BN is 50% of the new oil BN. So if the new oil BN is 10, the caution limit should be set at 5 and a critical BN level of 2. For trending of used oil use ASTM D974, D4739 or D5984-96.

You need to send a new sample of the oil in question to your lab to get a baseline BN. You can set your limits after you get this information. The BN will be slightly different for each type/brand of oil. You should use BN as an indicator of a more serious problem. Even though your test results for contamination, oil condition and wear are all normal, you need to reference your BN results against specific ASTM test results to locate a problem.

Jason Kopschinsky, Technical Consultant, Noria Corporation