Water supply active protection systems

Hydrants should be considered as a backup water supply source to monitors and fixed fire suppression systems. Hydrants should be located on the ring main at intervals to suitably direct water on the fire hazard with a fire hose. Hydrants monitors and hose reels should be placed a minimum of 15 meters (50 ft.) from the hazard they protect for onshore facilities. Hydrants in process areas should be located so that any portion of a process unit can be reached from at least two opposite directions with the use of 76 meters (250 ft), hose lines if the approach is made from the upwind side of the fire. Offshore hydrants are located at the main accessways at the edge of the platform for each module. Normal access into a location should not be impeded by the placement of monitors or hydrants. This is especially important for heavy crane access during maintenance and turnaround activities. 

Water spray only 0.25 gpm/ft (10.2 Ipm/m ) of wetted surface 0.10 gpm/fT (4.1 Ipm/m ) of wetted surface Active protection dependent on detection, actuation and fire water supply systems. 

Where water supplies are inadequate for conventional firefighting and foam making, automatically activated fixed clean agent or CO2 systems may be considered for seal fire protection. The agent should be discharged into the seal area below the secondary seal. Fire detection options for these automatic systems include reusable thermal wires and pneumatic tube devices. Thermal wire is typically the more economical choice. 

When considering the application of foam to hazardous material spills, key requirements include an adequate water supply, the foam concentrate, appropriate proportioning equipment, piping, foam makers, and discharge devices and protective equipment for the personnel involved. Activation may be automatic, but in most cases it is manual. There are four types of application systems. They include fixed, semifixed, mobile, and portable (NFPA 11, 1988). 

The sulfuric acid plant has boiler blowdown and cooling tower blowdown waste streams, which are uncontaminated. However, accidental spills of acid can and do occur, and when they do, the spills contaminate the blowdown streams. Therefore, neutralization facilities should be supplied for the blowdown waste streams (Table 15), which involves the installation of a reliable pH or conductivity continuous-monitoring unit on the plant effluent stream. The second part of the system is a retaining area through which non-contaminated effluent normally flows. The detection and alarm system, when activated, causes a plant shutdown that allows location of the failure and initiation of necessary repairs. Such a system, therefore, provides the continuous protection of natural drainage waters, as well as the means to correct a process disruption. 

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