Fire water pumps

Figure 15-23. Fire water pump insulation is not necessary because the exhaust is not in a work area and the fire water pump is not in a classified areo (more than 10 ft from production equipment, oil storage, etc.)...

Emergency equipment, such as diesel-driven fire water pumps and generators. 

Safety Systems Fire-Fighting Systems Fire Water Pumps... 

Taxonomy No. 4 2 4 2 Equipment Description PROTECTION SYSTEMS-FIRE-FIRE WATER PUMPS-ELECTRIC ... 

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. 

For onshore facilities, water may be supplied from local public water mains, storage tanks, lakes and rivers. In these cases a conventional horizontal pump is used. The preferred design for onshore fire water pumps is a horizontal centrifugal type with a relatively flat performance curve (i.e., pressure versus quantity). The discharge pressure is determined by the minimum residual pressure required at the most remote location of the facility flowing its highest practical demand with allowances added for piping friction losses. 

When more than one pump is installed, they should be coordinated to start in sequence, since immediate start up of all pumps may not be necessary and could cause damage to the system. Depending on the number of pumps available, they can be set to startup on sequentially decreasing fire main set points. All fire water pumps should be able to be started from remote activation switches located in manned control rooms. 

Fire water pumps from adjacent areas... 

Main fire water pump(s) from reserve fire water pump(s) when these pumps provide the only source of fire protection water... 

When a booster fire water pump takes suction from a public main, the design should be such that operation of the pump at 150% of rated capacity will not reduce the public main pressure below 20 psi (137.9 kPa). Provisions against contamination of the municipal system should be made by adding a backflow device is typically required. Local agencies generally have specific requirements. Some locations do not allow direct suction from public water mains. 

Fire water mains should be designed to handle the maximum pressures developed by fire water pumps. Systems operating at pressures over 150 psi (1,034 kPa) are discouraged, as this would exceed the normal design pressures for most fire protection assets such as monitors, hydrants, etc. 

It is common practice to provide pumping capacity so that when the largest fire water pump is out of service, the total fire water demand can still be met. In situations where the demand does not exceed 1,500 gpm (5,700 Ipm), it may be acceptable to use a single pump. 

Listed or approved equipment should be specified for fire water pumps, drivers, controls, and associated equipment. The use of unlisted or unapproved equipment is acceptable if it is of equivalent construction and designed for fire services as specified in NFPA 20. 

Fire water pumps should be dedicated solely to fire protection. They may be used to feed into a backup system for emergency process cooling, but not as the primary supply. Valving for this connection should be accessible for prompt shutdown when required under fire emergency conditions. 

On large fire water systems, the location of pumps and storage tanks at various plant areas provides greater reliability of protection and results in less pressure drop between the pump and the area of demand. Net positive suction head (NPSH) requirements and friction loss in the piping should be considered in locating fire water pumps. 

Horizontal centrifugal pumps should provide 150% of the rated capacity at 65% of the rated pressure, with a shutoff head of not more than 120% of the rated pressure. This pump should be used only when suction supply is under a positive head. Suction pipes should be designed to preclude the formation of air bubbles. A characteristic curve for a rated fire water pump is shown in Figure 7-15. 

Percent of Rated Capacity Figure 7-15. Rated Fire Water Pump Curve... 

Pressure maintenance (jockey) pumps should be provided to maintain a predetermined pressure on the system and make-up normal leakage in the distribution system. Normally, the pressure maintenance pump will maintain 10-15 psi (69-103 kPa) above the starting pressure for the automatic starting of the main fire water pump. (See 7.4.4.3.9.)... 

When the fire water system will be routinely used for purposes other than firefighting (e.g., washdown), the pressure maintenance pump, typically 150-300 gpm (570-1,150 Ipm), should have sufficient capacity for such use or a separate service pump should be provided. The service pump need not meet the requirements for fire water pumps. 

Fire Water Pump Driver and Miscellaneous Equipment... 

The acceptable drivers for fire water pumps are electrical motor and diesel engine. If only one driver is used, it should be a diesel, unless the reliability of electrical power can be ensured by onsite diesel emergency power or there are two independent reliable power supplies. 

The diesel engine is the most dependable engine for driving fire water pumps and should be the only type of engine acceptable for this service. The following minimum equipment should be provided for diesel engines ... 

The recommended location for the diesel fuel tank is outdoors, just outside of the building. Where location of the diesel fuel storage tank outside of the fire water pump building is not appropriate (cold weather), sprinkler protection of the fire-water pump house is recommended. Pump controllers should be sealed and splash resistant. 

The reliability of the power supply should be determined, taking into account the frequency of power outages and extent of interruption. Consideration should be given to connecting electrically driven fire water pumps to the emergency power system, where one exists. 

A controller should be provided for each fire water pump. The controller should be designed and installed in accordance with NFPA 20 specifications. An example fire water pump controller is shown in Figure 7-16. 

The basic methods of starting fire water pumps are automatic, remote manual, and local. All pumps should be arranged for local manual shutdown only at the pump. 

Remote controllers for fire water pumps or remote operational status indicator panels for sprinkler systems and fire water pumps will typically be protected according to the protection protocol of the room or building in which they are housed. 

The only acceptable method for shutting down a fire water pump is by means of a local "stop" push button. 

Other supervisory signals may come from fire protection system components such as supervised control valves, system air and supervisory air pressure transmitters, water tank level and temperature transmitters, valve house and fire water pump building temperature transmitters, and fire water pumps. 

Numerous vendors build complete lines of fire trucks. The configuration of the truck is designed to meet the needs of the site. The types of trucks vary from water pumper trucks, foam pumper trucks, combination water and foam trucks, aerial trucks, and ladder trucks. Sizing of the fire water pumps on the trucks varies from 500 to 4,000 gpm (1,900 to 15,000 Ipm). Foam storage on the trucks varies from 250 to 2,000 gal (950 to 9,500 I). 

New fire water pump installations require acceptance testing as defined in NEPA 20. This section highlights some of the important tests required. 

The fire water pump should be flow tested to determine its performance. The flow test should validate the certified fire water pump curve provided by the manufacturer. The fire water pump should run for at least 1 hour. 

All actions required of the controller must be function tested. The test requires startingthe fire water pump six times automatically and six times manually. Following each start, the pump must be run at rated speed for at least 5 minutes. 

The first fireball, at approximately 11 10 A.M., caused an operator fatality and a contractor injury. Emergency response was impaired because the fire water pumps were down. The fire spread to the catalyst storage tanks. A subsequent explosion of an adjacent catalyst storage tank resulted in the injury of four firefighters. Extinguishment of the fire was accomplished by the local fire department and plant fire brigade at 12 10 P.M. 

The No. 2 diesel fire water pump was down because its batteries were dead. The dead batteries were detected and recharged in the 7/3/2001 monthly check, but they were not replaced or rechecked. (Mechanical integrity)... 

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