Main fire pumps

Main fire pumps should be automatically controlled to start whenever there is a demand that reduces system pressure below a set point of say 7 barg. They should be large enough to keep the pressure above that set point at the most distant hydrant and at the system design flow rate. Spare pumps should be diesel engine driven with independent fuel tanks. Where steam is available, steam-driven pumps may be used to supplement the electric- and diesel-driven units. 

Electrical Substation Water treatment plant Cooling tower Air compressors Parking lot Main water pumps Warehouses that contain non-hazardous, nonexplosive, and nonflammable materials Fired heaters All ignition sources... 

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. 

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

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.)... 

NFPA 20—Standard for the Installation of Centrifugal Fire Pumps NFPA 24—Standard for the Installation of Private Fire Service Mains and Their Appurtenances... 

If a fire occurs in one of the zones a fusible link will fail, causing the pressure control deluge valve (PCDV) to open and the main fire water pumps to start. Water will flow out of the sprinkler heads in that zone only. The PCDV can also be tripped manually. 

The water supply for a sprinkler system must be reliable, automatic, capable of supplying the flow of water at the appropriate pressure and not subject to freezing or drought. The supply source can be town mains, automatic pumped, elevated private reservoir, gravity tank or pressure tank. Where pumps are used at least two must be installed, one working and one spare, from separate power supplies, e.g. electric and diesel, and automatic start-up. The water within the system must be free from debris which may block the sprinkler heads. The amount of water and its pressure is a function of the hazard rating of the fire risk and is given in Table 25.9. 

The fire hazards analysis conducted for the Rovno NPP Unit 3 (under construction) identified several weaknesses. The results are also planned to be used for making in Unit 4. These relate to the replacement of fire doors, overlayers for cables, penetrations and connections between fire areas, the spatial separation of the two control rooms and the use of non-combustible fluids for the lubrication of the main coolant pumps. 

Low-pressure feed heater, the deaerator and the high-pressure feed heaters Three main feedwater pumps Two start-up feedwater pumps Switchgear rooms Electrical equipment room Lube oil storage tanks Motor-driven fire pumps Air compressors... 

A water supply system ineluding the fire pumps, yard main, and interior distribution piping. 

To avoid common failure incidents, prime mover and backup fire pumps preferably should not be located immediately next to each other and ideally should be housed at separate locations at the facility. They should feed into the firewater distribution at points that are as remote as practical from each other. In practical applications, except for offshore installations, most small to medium sized facilities contain a single firewater storage tank, requiring the siting of all firewater pumps close to it. Even in these circumstances it may be wise to segregate the main and backup fire pumps from each other with tie-in points to the firewater distribution loops. This mostly depends on the hazard level of the facility and... 

Start the fire pump to be tested and let it run for a minimum of 30 min, for stabilization of the mechanical systems. The firewater pump can be started manually from the controller, but it is typically preferred that a local fire water device is opened (i.e., fire hydrant(s)) to simulate firewater pump auto-start on low fire main pressure detection. If several fire pumps are arranged to start in sequence, the sequence startup should be verified to confirm programming logic arrangements. Adjust the driver (i.e., engine) rpm to operate the pump as close as possible to the rated rpm performance curve. 

Water. Water mains should be connected to plant fire mains at two or more poiats, so that a sufficient water supply can be deHvered ia case of emergency. The plant loop and its branches should be adequately valved so that a break can be isolated without affecting a principal part of the system. If there is any question of maintaining adequate pressure, suitable booster pumps should be iastaHed. Any connection made to potable water for process water or cooling water must be made ia such a manner that there can be no backflow of possibly contaminated water check valves alone are not sufficient. The municipal supply should faH freely iato a tank from which the water is pumped for process purposes, or commercially available and approved backflow preventers should be used. 

Gulf of Mexico, Main Pass Block 133, Fire Unmanned platform, pump packing leakage Estimated loss at 5,500,000... 

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. 

Quite often jetties are fitted with their own water pumps, taking suction into the sea or river. The jetty fire water grid is often connected to the main plant fire water system as a backup. Care should be taken to avoid seawater corrosion of the main site fire water system. 

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. 

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