Firewater distribution system

The sizing of piping is based upon a hydraulic analysis for the water distribution network for the WCCE. The main delivery pipe should be sized to provide 150% of the design flow rate. A residual pressure and flow requirement at the most remote hydrocarbon process or storage location from the supply source dictates the sizing for the remaining system. Normal reliability requirements usually suggest that minimum of two sources of supply be available that are in themselves remote from each other. Therefore two remote flow calculations must be performed to determine the minimum pipe distribution size. NFPA 24 requires that the minimum residual pressure available in a fire main not be less than 6.9 bars (100 psi.). Velocity calculations should be performed which verify flows are not more than the limits of the material that is employed. 

The firewater system should be dedicated to firewater usage. Utilization for process or domestic services, erodes the function and capability of the firewater system, particularly its pressure, possibly during an emergency. 

A hydraulically designed system is preferred over standardized approach for optimization of the firewater flows, water storage requirements and piping materials. In any case, the main header should not be less than 203 mm (8 in.) in diameter. Piping routed to hydrants, monitors, hose reels and other protective systems should be at least 152 mm (6 in.) in diameter. 

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Several catastrophic fire incidents in the petroleum industry have been the result of the facility firewater pumps being directly affected by the initial effects of the incident. The cause of these impacts has been mainly due to the siting of the fire pumps in vulnerable locations without adequate protection measures from the probable incident and the unavailability or provision of other backup water sources. A single point failure analysis of firewater distribution systems is an effective analysis that can be performed to identify where design deficiencies may exist. For all high risk locations, fire water supplies should be available from several remotely located sources that are totally independent of each and utility systems which are required for support. 

Testing of firewater distribution systems is accomplished to determine if the condition of system is adequate to support a WCCE need for firewater. The condition of piping, leaks, existence of closed valves or sediment, operability of valves and monitors, etc., should be determined annually. 

Power-generation plants Heat exchangers and condensers Firewater distribution systems Intakes As above for heat exchangers and fire protection systems Under mussels and other fouling organisms on intakes... 

The firewater distribution system should be pressure tested regularly (at least... 

Process facilities susceptible to earthquakes should be provided with suitable restraints for fire protection systems. The extent of these restraints are normally dictated by local ordinances and primarily concern the bracing of pipework and adequate securing of firewater pump base plates and controller panels for earthquake forces. Pump houses should be adequately constructed and braced so they will not collapse onto the firewater pump or distribution piping. 

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