Coil coating ovens typically operate at high temperatures, with some zones at over 800°F. This temperature range is needed to cure organic polymer coatings to their substrate materials.
Solvents are typically vaporized in the early oven zones. At the same time other materials are also vaporized: resins, plasticizers, additives, and other compounds. Most monitoring problems arise because these materials condense when the sample temperature drops. The oven atmosphere materials condense in the sample lines and the analyzer because the temperature is too low to maintain a vapor state. In very little time, the sample lines, analyzer, and sample pump can become fouled and clogged.
Besides the frequent downtime needed to dismantle and clean the system, most analyzers are inaccurate when monitoring varying types of solvents or coatings. That's why fire codes and safety laws specify that coil coating processes must use continuous solvent vapor analyzers when ovens are designed to operate above 25% of the Lower Flammable Limit (LFL).
The analyzer used must meet certain basic requirements as well as several provisions specific to coil coating. It should be excellent in high temperature processes, have a fast response time, provide a uniform response to a wide range of solvents, be failsafe and require little maintenance.
Find out more about LFL Monitoring in Coil Coating Ovens