Sample conditioning and
how improving it can help your analyzer.

In his book Industrial Sampling Systems – Reliable Design & Maintenance, Tony Waters quips that 80% of an analyzer’s downtime is caused by improper sample conditioning. While the specifics of this rumor may be up for debate, the fact remains that designing a successful sampling system is crucial to the overall success of any process analyzer. Very rarely are process analyzers able to accept a process sample without first making the sample compatible with the analyzer.

Sample conditioning can best be described as the adjustments made to the conditions of a sample so that the sample simultaneously does not harm the analyzer but still remains representative of the original process. Typical steps include adjusting the physical conditions of the samples, mitigating the effects of interference, while also ensuring the sample is characteristic of the process as a whole.

Take a hypothetical example of a spectrometer measuring the composition of a condensable gas. Spectrometers perform this measurement by exposing a sample to light and observing changes in the returning light to determine the sample’s composition. Any suspended particulate or droplet has the potential to scatter light and interfere with the measurement. On the other hand, condensable gases at the correct temperature and pressure can form droplets of liquid, both on the lenses of the analyzer as well as suspended in the sample fluid. In this example, the physical conditions of the sample work to create an interference that affects the reliability of the measurement.

However, this can be readily avoided by ensuring that the sample is not transported at or near its dew point. The typical rule of thumb is that a sample should be held at least 10 degrees Celsius above its dew point to prevent this issue from occurring. Potential sampling mishaps like the one mentioned above, or others not mentioned here can often be avoided by following these rules of sampling:

• Pay attention to pressure.
• Don’t move a gas at its dew point.
• Don’t move a liquid at its bubble point.
• Avoid dead legs.
• Assume valves will leak.

If you’re looking to upgrade or replace an analyzer system but are unsure where to start, feel free to reach out to one of our team members today. They have decades of experience doing exactly this.