Servomex gas analyzer meets USCG requirements.

Callidus Technologies, the Tulsa-based combustion and environmental protection specialist, has purchased several systems utilizing two Servomex 1900 oxygen analyzers and a sampling system meeting the strict U.S. Coast Guard (USCG) requirements for monitoring ships being loaded with volatile liquids at marine terminals. The Servomex system provides accuracy, reliability and speed of response required.

When ships are loaded with liquids such as gasoline, fuel oils or naphtha, vapour is displaced from the hold. This vapour can either be recovered or, as in this case, destroyed using an enclosed flare. The composition of the displaced vapour is highly variable and under certain conditions can fall within the flammability limits of the gas. Natural gas is used to enrich the vapor to ensure that the combustibles are maintained above their U.E.L. (upper explosive limit). An oxygen analyzer is used to monitor and control mixture to ensure that a hazardous situation does not arise. Because of the safety-critical nature of this application, two oxygen analyzers are used in a redundant voting arrangement. If the oxygen level is detected as being above the control point, action must be taken within 30 seconds.

Piping to the two analyzers was designed to be of equal length from the sample take-off and the sampling system was configured so that the analyzers could be calibrated concurrently, with only a single control point for the gas inlet for calibration and sample. Another design feature was the coalescing/membrane filter that is installed in such a way that it is continuously drained so that condensate does not collect. Early tests with the Servomex system showed that the response time was in the order of five seconds, and the two analyzers could easily read within 1 percent of the measured range.