MOSS Unit Samples Flue Gas From Process Heaters During Pre-Startup Safety Check

Principal Technology Inc. introduces a combustible methane, other hydrocarbons and oxygen sampling system (MOSS) designed to sample the flue gas from process heaters during the pre-startup safety check. Principal Technology’s MOSS was designed to reduce operational downtime by utilizing a high-flow, rapid sample system to shorten the time necessary to confirm it is safe to start a process heater.

The Principal Technology MOSS samples and verifies that the natural draft purge cycle has cleared the heater combustion chamber of combustible gas mixtures, in accordance to the National Fire Protection Agency (NFPA) 87 recommended practices for fluid heaters. The MOSS works with an integrated burner management system (BMS) to confirm that inlet air registers and outlet dampers are in the fully open position to admit purge air as part of the pre-ignition safety check.

The MOSS includes an integral dual-mode sampling system that uses an initial high-flow rate to minimize the transit time required to pull the heater sample from the stack. Then the system tests for gas at the slow sample flow rate required to achieve detection instrument accuracy. This two-stage sample process usually operates for less than two minutes, depending on heater configuration.

The Principal Technology MOSS can reduce stack sampling time by 30 percent or more compared to other systems on the market and still meet all NFPA requirements for safe burner operations, according to Principal Technology. The MOSS sampling system also includes automatic system “bump” test and calibration capabilities, and inlet filter dryers and automatic sample system back-purge to prevent condensate accumulation from combustion products when the system is not active. An optional multi-point sample configuration is available for large process heaters or heaters with multiple flue stacks.

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