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In This Issue:

• Today's Tip: Hot Sampling Problem Solved

• Book Bits: Protecting Against Water Contamination

• Lube-Trivia: Viscosity Variations

• Q & A: Don't Delay After Sampling

Today's Tip

Hot Sampling Problem Solved

• We use five-ounce plastic bottles to collect oil samples with vacuum pumps. On hot days or when sampling hot oil, the bottles collapse under the vacuum pressure. To prevent this, I make sleeves from clear PVC pipe, with the inner diameter matching the diameter of the bottles. Before collecting the sample, I ask the technician to slide the bottle into the sleeve and then pull the vacuum. The sleeve reduces the incidence of bottle collapse by constraining the out-of-round shape change that the bottle must undergo just prior to collapse. (Submitted by Stephen French, Sr. Engineer, PPL Generation. Thanks Stephen!)

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Book Bits

Protecting Against Water Contamination

From "Total Contamination Control 2000"

An important aspect that must first be considered in any system is its protection from external water ingression. A correctly designed and sealed system can potentially eliminate a number of water ingression problems and improve the effectiveness of the water removal device employed. The application of a suitable breather filter that is oleophobically treated to retard the ingression of sprayed water and steam, has proven to be highly effective. The breather should also be elevated onto a standpipe, which will stop the ingression of water and contaminant that collects on top of reservoirs. The use of desiccant-style breathers may also be considered to combat the effects of reservoir condensation by drying out the incoming air. A reservoir that is sealed during operation, with oil top-up filling points, will also minimize external water ingression.

More information about the book "Total Contamination Control 2000"

Lube-Trivia

Viscosity Variations

Test your knowledge and prepare for ICML lubrication and oil analysis certification with Lube-Trivia.

QUESTION: What is the difference between oil viscosity and
grease apparent viscosity?

For the answer, visit: http://www.lube-tips.com/trivia/20031022.asp

Q & A

Don't Delay After Sampling

"After pulling a sample from a piece of equipment, will the oil sample change within the sample bottle? If so, what is the longest amount of time we should allow the sample to sit?"

The moment an oil sample is taken from a machine, the sample and the oil in the reservoir begin to experience different environments.

As one might imagine, at that point the properties of the two bodies begin to deviate from one another.

The greater the period between sampling and testing, the greater this deviation will be. Yes, the properties of the sample can change over time. However, the in-service oil is more likely to experience significant change.

Once taken, samples should be tested as soon as reasonably possible. To determine a time limit for shipping samples, consider the scope of the oil analysis program as it applies to the particular component. In particular, the sampling frequency should be considered.

If the sampling frequency is monthly, the samples should be tested within days. If the frequency is six months, immediate testing may not be so critical. Generally, one week is a reasonable maximum to allow samples to sit.

It is not uncommon for samples to sit for weeks or even months before they are sent for testing. After several weeks, the sample is no longer representative of the oil in the machine and the value derived from testing is significantly diminished.

One of the common delays for shipping samples is the associated paperwork. This process can be overcome by working with the lab to set up preprinted sample labels and maintaining an accurate database of the machines and their oil analysis history. Once the system is set up properly, the labels may require no more than the unit ID number and the sample date.

Jarrod Potteiger, Technical Consultant, Noria Corporation

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