Deluge system

If an ethyl ether fire occurs, carbon dioxide, carbon tetrachloride, and dry chemical fire extinguishers meeting National Eire Prevention Association Code 1 and 2 requirements may be used successhiUy (23). Water may also be effectively appHed (see Plant safety). Hose streams played into open tanks of burning ethyl ether serve only to scatter the Hquid and spread the fire. However, ether fires may be extinguished by a high pressure water spray that cools the burning surface and smothers the fire. Automatic sprinklers and deluge systems are also effective. 

The use of appropriate instruments to monitor equipment operation and relevant process variables will detect, and provide warning of, undesirable excursions. Otherwise tliese can result in equipment failure or escape of chemicals, e.g. due to atmospheric venting, leakage or spillage. Instruments may facilitate automatic control, emergency action such as coolant or pressure relief or emergency shutdown, or the operation of water deluge systems. 

The third line includes fixed fire protection systems (sprinklers, water sprays, or deluge systems, monitor guns, etc.), dikes, designed drainage systems, and other systems that control or iiiitigaic ha. ardous releases. 

To protect against structural failure, water-deluge systems are usually installed to keep vessels and structural steelwork cool in a fire. 

A water spray protection system around vessels is recommended to prevent this type of failure. These water spray protection systems, commonly called deluge systems, are designed to keep the vessel cool, flush away potentially hazardous spills, and help to knock down gas clouds.13 Deluge systems can also provide enough time to transfer material out of a storage tank into another (safe) area. 

Vessel deluge systems are usually designed as open-head systems, which are activated when a fire is detected and/or a flammable gas mixture is detected. The deluge system is usually opened when the flammable gas concentration is a fraction of the LFL (approximately 25 %) or when a fire is detected through heat. Table 7-7 provides descriptions and design specifications for these systems. 

Fireproofing Insulate vessels, pipes, and structures to minimize damage resulting from fires. Add deluge systems and design to withstand some damage from fires and explosions e.g., use multiple deluge systems with separate shutoffs. 

Control rooms Water supplies Design control rooms to withstand explosions. Provide supply for maximum demand. Consider many deluge systems running simultaneously. Diesel-engine pumps are recommended. 

Control valves for deluge Manual fire protection Separate units Place shutoffs well away from process areas. Install hydrants, monitors, and deluge systems. Add good drainage. Separate (space) plants on a site, and separate units within plants. Provide access from two sides. 

Determine the water requirement (gpm) and number of nozzles for a deluge system required to protect a 10,000-gal storage tank that has a diameter of 15 ft. Use 0.5-in nozzles with a nozzle pressure of 35 psig, and assume that the vessel contains a reactive solvent. 

The process area has combustible gas detectors, fireproofing, and a water deluge system. Cable trays are protected with deluge, and portable dry chemical extinguishers are in the process area. Diesel-powered fire water pumps can provide a maximum fire water demand for 4 hr. 

Loss control features include combustible gas detectors installed around the containment area and transfer system. A diesel-driven fire pump is capable of handling the emergency demand for 4 hr. A water deluge system has been installed around the storage tank and transfer pump. 

Block valves are often controlled on the basis of analyzer results, such as area monitors for detecting solvent leaks, reactor analyzers for detecting runaway reactions (a block valve can be opened to add a reaction inhibitor or to turn on a deluge system), sewer analyzers for detecting high concentrations of contaminants, and vent analyzers to detect high levels of contaminants. 

This accident was attributed to the lack of design protection to prevent the backup of ammonia into this storage tank. It also appears that mitigation techniques were not part of the system (deluge systems, dikes, and the like). 

The magnitude of this accident could have been reduced with (1) improved pipe design, (2) improved deluge system design, (3) backup or more secure electrical supply, and (4) installation of detection analyzers and block valves. 

This accident could have been prevented by a good inspection and maintenance program. Potential design improvements include vibration detectors, gas analyzers, block valves, and deluge systems. 

The Detonator Module is a control unit that is used with the UV and/or IR detection system to activate the water deluge system. 

To successfully control a deflagration, large volumes of water must be applied quickly in a manner that will completely envelop the fuel. This is achieved by using a deluge system, by which water is simultaneously discharged from all outlets in the system, totally enveloping the hazard. 

A typical high speed deluge system uses an electrically actuated (solenoid or squib) valve to initiate the flow of water from the nozzles. See Figure 9. The valve is positioned as close to the nozzles as possible. The piping between the valve and nozzles is fully primed and contains few if any air bubbles. 

Many factors must be considered when designing an effective high speed deluge system. It is important that the response time criteria be realistic and that it be defined in a manner that will permit meaningful testing of the completed installation to ensure that the design criteria have been met. 

For only if the detection system and water deluge system work together to perform their functions in the shortest length of time will consistently reliable protection be possible. 

Advancements In Electronic Fire Detection in the past fifteen to twenty (15 to 20) years has made Ultra High Speed Deluge Systems for explosive facilities quite feasible and reliable. Since Detection has been covered in previous chapters, this chapter will focus mainly on Ultra High Speed Deluge Fire Suppression. Discussed are the three (3) most popular ultra high speed fire suppression systems presently used in explosive facilities. 

---