What does a low flame test on a vapor meter involve?

A low flame test on a vapor meter specifically involves passing air at a designated static pressure through the meter, which is typically set at 1.5 inches of water column (H2O). This procedure is essential for assessing the meter's ability to accurately measure vapor flow under low-pressure conditions. During this test, the meter is calibrated to ensure it can operate effectively and maintain accuracy when measuring vapor at these lower pressures, which are common in various applications.

The pressure of 1.5 inches H2O strikes a balance that allows the testing of the vapor meter without overly stressing its mechanical components, ensuring reliability and performance are adequately evaluated. This testing process is vital because it simulates actual operating conditions where the meter might experience low pressures, making it a key step in ensuring the instrument's accurate measurement capabilities in practical use cases.