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In This Issue:

• Today's Tip: Paper Thermometer Reveals Temperature Spikes

• Book Bits: Pressure Indicators Provide Early Warning

• Q & A: Particle Counter Results Differ

Today's Tip

Paper Thermometer Reveals Temperature Spikes

• In time-critical situations where real-time infrared thermography is impractical and thermocouple/recording equipment cannot be installed, consider temperature-sensitive tapes. These tapes are manufactured in a variety of sensing ranges and will clearly record the peak temperature that a machine area reached since the tape was first applied. A quick visual check is all it takes to read the "paper thermometer". (Submitted by Mark Smith, Technical Administrator, Analysts, Inc. Thanks Mark!)

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Book Bits

Pressure Indicators Provide Early Warning

From "Total Contamination Control '98"

Differential pressure indicators are used to give warning of impending filter blockage. The pressure at which actuation occurs depends upon the setting of the bypass valve chosen and is usually set at about 70 percent of the bypass cracking pressure. This gives a safety margin so that element change can be effected at a convenient time before bypassing occurs.

More information about the book "Total Contamination Control '98"

Q & A

Particle Counter Results Differ

"I have recently purchased an on-site portable particle counter allowing me to take immediate action on out-of-condition results. However, my instrument results seem to be lower than the results I receive from the laboratory. Is my new instrument at fault?"

Ownership of an on-site instrument is indeed a valuable addition to your program. However, do bear in mind the difference between taking a bottle sample and attaching your instrument directly online with the system.

Effectively, your instrument is giving you a direct insight to the system cleanliness without the corruption of potentially poor sampling procedures such as insufficient test port flushing, ambient contamination levels, and questionable bottle cleanliness.

My experience suggests that a difference of three ISO code values is the norm when comparing a laboratory result to an instrument, and may stretch to even wider differences. A difference of three codes is effectively a sample that is eight times dirtier - which when concentrated in a small sample bottle, is understandable.

However, proactive practitioners have successfully used laboratory bottle sampling to monitor their cleanliness levels, but I suggest you either make adjustments in your target cleanliness levels for the instrument, or set the targets based on bottle sampling, but monitor for sudden changes in the instrument cleanliness results that may not exceed the target caution/ critical levels.

Martin Williamson, Senior Technical Consultant, Noria UK Ltd.

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