TABLE OF CONTENTS Analyzers are used to measure analytical values. The most frequently used analyzers in the process industries are pH and conductivity analyzers. Of all the typical measurements, such as flow, level, pressure, and so on, process analysis tends to be the most difficult, the least under-stood, the most troublesome, the most expensive, and the most difficult to maintain. It is therefore imperative that the user handles process analysis carefully and gives it the time (and money) required for a successful installation. Laboratory and portable analyzers will not be discussed in this handbook.
When selecting an analyzer, the user should preferably choose a time-proven off-the-shelf device. Custom-built analyzers tend to have debugging problems and lead to difficult and expensive maintenance.
The cost of implementing an analyzer system is typically much higher than the cost of the analyzer itself. An analyzer system may include a sample probe, a sample line, a shelter, sample disposal equipment, and calibration gases. In addition, ongoing maintenance costs includes the cost of maintenance personnel and their training, the replacement of calibration gases, the cost of the calibrating equipment, and utilities.
When deciding upon the location of an analyzer, there are two possibilities: extractive and insitu. Some analyzers are mounted remotely from the sample point; these are known as "extractive" analyzers. This approach is implemented when the process conditions are severe, when the sample point is practically inaccessible, or when the analyzer's capabilities require it (e.g., it is not built for an industrial environment). Extractive-type analyzer systems...
