I have set up a PM to change out synthetic oil in gear boxes every 24 months. Three months before the PM kicks out to change the oil, I have another PM kick out to sample the oil before I change it. If the sample comes back with no issues, postpone the oil change another six or twelve months, whichever is best for the gear box in use. (Ron Utt, PM Team, Weyerhaeuser)

Plan now to attend Machinery Lubrication Level I training in 2006. Dates and locations here.

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Book Bits: Plan for Best Practice Lubrication

From the book "Maintenance Planning and Scheduling Handbook"

Lubrication is the most commonly recognized portion of a PM program. Unfortunately, an improper lubrication PM can be more damaging to equipment than having no PM service at all. For instance, many times a technician introduces dirt into a bearing by not wiping a grease fitting beforehand. Although general technician skill should prevent such practice, PM plans can help by including rags for wiping. PM plans can also specify removing old grease where components can be dissembled. PM plans can also guard against using oil with any chance of moisture content by specifying new containers where practical.

More information about the book "Maintenance Planning and Scheduling Handbook"

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

Question: What lubrication condition could you expect to find in a malfunctioning electric motor running at high temperature?

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"What type of relationship can one associate with iron particles when performing a spectrochemical analysis versus a direct-read ferrography? I believe spectrochemical determines the number of particles less than 8 to 10 microns and the direct read ferrography determines the number of iron particles greater than or less than five microns. I would think that if I have a certain value of iron particles from the spectrochemical I would not see a larger number in the direct read; however, I quite often do -why?"

You are correct that the spectrometric elemental analysis (usually ICP) has a size limitation. The upper size limit of a particle that the ICP can detect is usually quoted at about 5 to 8 microns. To detect (ferrous) particles greater than this, one must use other techniques, of which ferrous density is one. Direct-reading (DR) ferrography is one means of determining the ferrous density of the sample.

In DR ferrography, the ratio of the large particle reading (DL) to the small particle reading (DS) is a function of the predominant wear mode. This comparison of the DL and DS is often represented as the percent large particles (PLP). In a corrosion situation, where the majority of the particles is extremely small, the PLP would be low. If surface fatigue is the predominant wear mode then the PLP could be expected to be high, as this wear mode is characterized by large particle generation.

Assuming the amount of ferrous debris in the sample is the same for the two situations described above, the spectrometric iron would be fairly high for the corrosion situation and low for the fatigue situation. This is as a result of the size limitation of the spectrometer.

Comparing the trends of elemental iron and ferrous density, in particular their changes relative to each other, is a useful tool in used oil analysis for determining the size ratio of the particles in the oil. Of course, if one does note excessive increases in elemental iron and/or ferrous density then exception tests should be carried out. These might include patch microscopy or analytical ferrography.

Ashley Mayer, Noria Corporation

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