LUBA RET. EX 076/077 RE-E - Laserfiche WebLink

: _j I I 'LL O yr_ - - DESIGN PRESSURE Most new standpipe systems are designed by hydraulic calculations. This ensures that the water supply, pipe sizes used, and pumps (if needed) will provide a certain flow and pressure at a specified number of hose connections in the system. The current NFPA 14 specifies a minimum design pres- sure for Class I systems of 100 pounds per square inch (psi) at a specific flow rate, which depends on the number of hose connections per floor. How- ever, it includes an exception that allows design pressures as low as 65 psi, if this will accommodate the fire suppression tactics. These minimum pressures are based on certain assumptions about the fire department equipment and tactics, as well as the fixed fire pump feeding the standpipe system. The designer should com- pensate if the equipment or tactics vary from these assumptions in a particular building or jurisdiction. This will ensure the adequacy of fire streams to assure the safety of firefighters conducting interior operations. A straight stream nozzle requires at least 50 psi to operate. With the friction loss in fire hose added, 65 psi at the hose connection will provide 50 psi to a straight stream nozzle with 250 gallons per min- ute (gpm) flowing through. 100 feet of 2'/2 inch fire hose. The same pressures can deliver 95 gpm through 100 feet of 1'14 inch hose. In 1993, NFPA 14 changed the minimum required design pressure from 65 psi to 100 psi at the hose connections. At the same time, this standard was revised to permit longer distances between hose connections and remote areas of a building. Currently, this distance can be up to 150 feet for buildings without complete sprinkler protection, and up to 200 feet for fully sprinklered buildings. The 100 psi design pressure will permit greater flows or longer hose lines, but only with the same straight stream nozzles. Many fire service organizations begin their attacks with fog or combination nozzles that generally require at least 100 psi to operate. This dramatical- ly increases the pressure requirements at the hose connection. If 100 psi is actually available at the connection, every combination of hose size and length will result in inadequate nozzle pressure. It is assumed that firefighters will use fog or combi- nation nozzles early in a fire situation, when only one or two hose lines are in operation. It is further 1 i i I i FIRE -SERVICE FEATUR.ES• OF BUI-LD.LNGS AND FIRE PROTECTION S-Y STEMS' 37 153 (Fig. 4.8) Sign to identify hose connection location in a shopping mall. (Fig. 4.9) Bollards and striping to create an access path in a parking garage. Bright signs at the top of column help to locate the valve.