Paint a magnet white and permanently attach it to the dipstick of the reservoir. It allows a better visual inspection of the color of the oil, and if there are particles stuck to it, you know you need to investigate more. (Ian Kirton, Hydraulic Specialist, Princess Auto)

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Hot Topics: Oil Cleanliness Codes

What's going on over at the Noria Message Boards? Here's an interesting post about contaminant cleanliness codes:

I was wondering how many people actually know what codes they are working to. I was surprised to find that many of the companies that I have been contracted to work for are still getting their test results in NAS 1638 and ISO 4406:87.

Most of these people were unaware that these codes were replaced more than 5 years ago. I think it is the responsibility of the labs themselves to make maintenance engineers aware that there have been updates.

How many people actually have labs with particle counters calibrated to ISO/FDIS 11171 standards? And do you think it is important?

Read responses to this post or submit your response.

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"Time-wise, how long does a turbine oil have to be at an elevated temperature before oil breakdown begins"

There is a test used to gauge the oxidative endurance of the new oil. On your product data sheet, look for the ASTM D943 test result (TOST). This test is conducted by heating the oil in the presence of water and a copper catalyst in a test tube to 95°C (203°F+) and bubbling oxygen at rate of 3 L/hr. The test result represents the number of hours it takes for the oil to begin degrading (acid number rise of 2) under this sustained temperature.

While it is impossible to precisely predict the life of the oil in typical service, it is estimated that the oxidation rate doubles for each 18°F decrease in temperature. Depending on how your machine environment compares to the TOST test conditions, you can try to make some assumptions.

For instance, if you have an average reservoir oil temperature of 50°C (120°F) and contaminant environment similar to the TOST test, you are looking at an oil service life approximately 16 times greater than the stated TOST result. So, given that the new oil has a TOST of 10,000 hours, the in-service oil at this lower temperature might have roughly 160,000 hours of life (about 18 years).

However, you are stressing the oil at elevated temperature and pressure each time it passes through the system, which works to reduce expected service life. Localized hot spots, pressure, turbulence, moisture, wear particles and air entrainment can all serve as pro-oxidants to accelerate oil degradation. This is usually offset by making up the reservoir every year with new oil (and antioxidants) and controlling contaminant levels.

Mike Johnson, Noria Corporation

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