Processes that are monitored for solvent vapor concentrations are typically enclosed, heated spaces that require an active sample drawing system. They have an intentional release of solvent at all times. In fact these processes are often optimized for speed and performance by safely releasing more solvent, not less; as they often operate near legal limits for combustible gas concentrations. This means the precise concentration of solvent vapors must be measured with a high level of accuracy while meeting the standard AND special requirements of a process application.
After determining whether the detection system your interested in is considered an analyzer (for process) or a sensor (for leak detection), the top ten questions to consider when selecting a flammability analyzer for a process application are:
- Is the sensor approved by Factory Mutual? Does the approval cover the entire device, including the sampling system, and not just the sensor element? Does this approval include the response to solvents, not just methane or propane?
- How quickly can the device make an alarm? Is the time-to-alarm less than a few seconds? Does this “time-to-alarm” include the “sample transport time,” that is, the time to extract a sample and deliver it to the sensor, and to filter it for particles and contaminants? If not, how much more time is needed?
- Is the specified response time true for solvents, not just methane?
- For the solvents to be measured, now or in the future, how different is the response of one to another? How much error results from measuring different solvents?
- Is it possible to easily mis-calibrate the sensor, so that it fails to give an alarm even though a flammable concentration is present?
- Can the device be calibrated according to code and still allow dryer operation without false alarms?
- Is the sensor and sampling system heated to a temperature above the Flash Point(s) of all solvents that are used, or might be used?
- Is the entire system heated to a temperature above the dew point, especially of water vapor? Can water vapor interfere with the operation of the device?
- Does the device remain accurate under the temperature or pressure changes that are expected?
- Is there a means to test and verify proper operation using a test gas? Is the test automated so it can be performed on a monthly basis as required by code?
For more information read our Selecting Flammability Analyzers for Process Applications article.