Fire and gas detection monitoring system in gas turbines

In a gas turbine package, usually, an automatic, electronically controlled fire and combustible gas detection and monitoring system is installed in the enclosure. A typical system description is provided below: The primary fire detection system uses multi-spectrum infrared (MIR) detectors. The system includes an automatic optical integrity feature to provide a continuous check of the optical surfaces, detector sensitivity and electronic circuitry of the detector-controller system, and automatic fault identification with digital display of system status in numerical code.

The article contains excerpts from the paper, "Gas turbine packaging options and features" by Klaus Brun of Southwest Research, Rainer Kurz of Solar Turbines, Joseph Thorp of Aramco Services Company, and Bernhard Winkelmann of Solar Turbines at the 2016 Turbomachinery Symposium.

The secondary fire detection system consists of rate-compensated thermal detectors. The two detection methods act independently in detecting and reporting a fire.

The fire and gas system control panel provides system supervision (for open circuit, ground fault, or loss of integrity), initiates alarm, release of fire suppression agent, and visual display of system status. The suppression system agent release is activated automatically with release solenoids located on the fire suppression skid. The suppression system can also be activated by an electrical push button on the turbine enclosure or manually at the suppression skid.

If a fire is detected, the detectors transmit an electrical signal to the fire and gas system control panel to activate the fire alarm and suppression system. The enclosure is equipped with two gas detectors: one at the turbine enclosure ventilation air inlet and one at the ventilation exhaust to provide continuous monitoring for combustible gases at the enclosure ventilation inlet and outlet.

The detectors are diffusion-based, point-type infrared devices that provide continuous monitoring of combustible hydrocarbon gas concentrations. The turbine start signal is interlocked with the fire and gas monitoring system to ensure the atmosphere is safe prior to initiating turbine engine start.

Most commonly, the enclosure is equipped with a CO2 fire suppression system consisting of a primary total flooding distribution system and a secondary metered distribution system. In the United States, the system is designed in accordance with the U.S. National Fire Protection Association Code 12.

A water mist system is also possible but is less common in the oil and gas industry. On detection of fire, the detectors transmit an electrical signal via the fire control panel to activate the fire suppression system release solenoids located on the fire suppression skid. On receipt of this signal, the solenoid actuated control heads activate the discharge valves on the primary and extended extinguishing cylinders, releasing the extinguishing agent into the enclosure.

CO2 pressure actuates the pressure trip operated dampers that close all vent openings. CO2 release control heads are also provided with manual release levers. Additionally, a weatherproof fire suppressant cylinder cabinet is sized to house the CO2 cylinders and is equipped with doors for servicing.

The manual pull levers are routed, by cable, to break glass pull stations on the exterior wall of the cabinet. CO2 cylinders are mounted on a weight scale with a preset alarm. Another frequently used fire suppression system uses water mist.