Steam Snuffing

Piping for snuffing steam injection into a heater firebox is required to help put out a fire if a tube mpture occurs. The snuffing steam isolation valve needs to be located at an accessible spot remote from the heater. Also, a remote fuel shutoff valve should be located adjacent to the snuffing steam valve so that both valves can be accessed quickly in case of fire. 

In applying the requirement for snuffing steam connections, 315°C should be used as an autoignition temperature criterion for typical hydrocarbon streams. 

Nozzles can be installed on the flame arrester honsing for injecting snuffing steam, carbon dioxide, or a suppressant into the arrester to extinguish a standing flame on the arrester element. 

Fired Heaters Liquid Spill Gas Release NFPA30 1. Hydrants 2. Monitors 3. Snuffing Steam 1. NFPA 24 2. NFPA 24 3. NFPA 86... 

Snuffing Steam - Pressurized steam (water vapor) used to smother and inhibit fire conditions. 

Examples of common safe practices are pressure relief valves, vent systems, flare stacks, snuffing steam and fire water, escape hatches in explosive areas, dikes around tanks storing hazardous materials, turbine drives as spares for electrical motors in case of power failure, and others. Safety considerations are paramount in the layout of the plant, particularly isolation of especially hazardous operations and accessibility for corrective action when necessary. 

Header boxes Most ends of tubes are connected by U-bends that make inspection difficult. Therefore, special return fittings with plugged connections are provided that permit inspection and cleaning. Because the removable plugs are subject to leaking, all headers must be completely enclosed in header boxes. Snuffing steam is used to suppress fire in this area. 

Header boxes, as shown in Exhibit 7-19, are enclosures around the fittings that connea two tubes. The fittings, called headers, are furnished with plugged connections for cleaning. The header boxes are sealed from the inside of the furnace by an insulated tube sheet, and, because this area is a possible source of fire, a snuffing steam connection is provided for fire suppression. A drain conneaion is so provided for leak deteaion. Clear access must be provided around the header box to permit inspeaion and tube cleaning or replacement. 

This section details the piping layout of circular and box-type furnaces. Although such special features as snuffing steam are actually required for both heaters, they are explained for one application only. 

Snuffing steam, which is used to suppress a fire in the header box in the convection or radiant sections, is supplied through local and remote manifolds. The remote manifold shoulintermediate pipe support column. If the local area is unreadi-able in an emergency, steam would be supplied from the remote manifold. The inlet and outlet control stations are located along the pipe rack adjacent to die furnace. This particular fiimat uses manually controlled valves for each burner. The burner supply headers—fuel gas, fire steam, and fuel oil—are run... 

Where vent stacks on hydrocarbon relief valves are susceptible to ignition by lightning, the use of snuffing steam should be considered. 

The tailpipe should have a 25-NB snuffing steam connection located 300 mm below the pipe outlet. 

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