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From "The Lubrication Field Test and Inspection Guide":

Internal Tank Inspections

It is not always possible to gain easy access to tanks, housings, casings, sumps, and other oil compartments. However, if possible, the internal conditions should be inspected by someone with a trained eye.

The headspace of many tanks maintains a continuous moist fog. This can lead to a build up of water in the oil, especially accumulations at the tank floor. The moisture in the headspace typically condenses on the ceiling then drips or runs to the bottom, forming puddles. Tanks like this are referred to as “rainmakers.” This can be observed by touching the inside ceiling with your fingers. If moisture is picked up (sometimes rust as well) the risk is great.

Heavy varnishing sometimes occurs inside of tanks and reservoirs. The appearance can range from gold-colored tank walls to thick dark deposits. Occasionally the “Fruit Roll-up” effect is observed when a putty knife is used to peel away a tarry adherent film. A varnish gauge can be used to rate the severity.

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Today's Tip

• When converting from one grease to another it may be helpful to determine how much soap residue you have resident in bearing housings and estimate how much flushing will be necessary to eliminate the old material. If the amount of old material is low and the residue is soft and pliable, then you may be able to simply increase the relube frequency, perhaps doubling the cycle for a while to flush out the old grease.

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Q & A

"I see that some oil analysis labs run base number tests using a hydrochloric acid reagent while others use a perchloric acid reagent. Is there any difference in the results produce by the two reagents?"

When performing the base number (BN) test (formerly total base number, or TBN) on used engine oils, it is best to employ a method that uses hydrochloric acid, not perchloric acid. For new oil, standard methods that employ both acid types will generally agree with one another. However, in used oils, the strong perchloric acid reacts with weak bases such as wear metals, whereas the reaction of weak hydrochloric acid is limited to the oil’s additive system (detergents, which supply reserve alkalinity).

Using the strong acid reagent to analyze used oils that contain interfering components can lead one to mistakenly conclude that the detergent additive is stable, when in fact it is depleted. Recommended ASTM standards include D974 (colorimetric) and D4739 (potentiometric). Avoid ASTM standard D2896 (potentiometric) for used engine oil analysis. However, if D2896 is used, a lower limit of 3.5 to 4.0 is recommended instead of 2.0 with D4739.

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