Dave Joseph here again. Today I wanted to blog about one of the most versatile uses of online analytical measurements. Although analysis might imply determining exactly what and how much of something is present, sometimes just sensing a change in conditions can justify the analyzer installation cost. A good example of this is in leak detection.
Many chemical plants use process water for various uses such as rinsing or cooling, and attempt to reuse the water as much as possible. Eventually, the process water is discharged, but if the water has been contaminated in the meantime, the process may escape into the environment. Common industry examples are polysilicon production (chemical/semiconductor), pulping liquor spills (pulp and paper), tailings ponds (mining), and steel pickling (metals processing). Negative outcomes can include lost product, extensive cleanup, and hazardous releases.
Frequently the releases start at low levels, but sudden releases are best observed with an online measurement like pH or conductivity. Choosing between pH and conductivity can be a little tricky because it depends on the sensitivity of the method, the baseline interference from the cooling water, and the response to increasing amount of the chemical leak. Generally, pH is preferred when the leak may be an acid (low pH) or a base (high pH) and the background does not have a lot of buffering capacity. Conductivity measurement is preferred when the leak may be a salt, the sensor location is hard to access, or when the background is relatively pure water. Measuring before and after a likely leak can increase sensitivity considerably. You can get more background on these methods by viewing the application notes Leak Detection with pH and Leak Detection with Conductivity.
Although constant monitoring for leaks can be a compelling reason to specify analyzers downstream of every possible source of water contamination, a more economical implementation of the concept is continuous monitoring of the return/used/contaminated water at headers with provision for portable measurement (of pH or conductivity) after every process unit. Thus, when a leak is detected, it can be traced to an individual source quite easily. Rosemount Analytical has excellent wireless analyzers that can be easily transferred from location to location to diagnose sources of leaks as needed. Thus, designing in an appropriate threaded connection provides for troubleshooting flexibility without the need for immediate commissioning of analyzers or untimely process shutdowns.
Have you used Rosemount Analytical products to detect leaks? Any tips? Share your experiences with others!