Fire Protection Philosophy and Design Guide

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF the number of fire monitors (refer to section 4.2.4.1) multiplied by the rated capacity of the monitor multiplied by plus all water/foam spray systems which release into those three envelopes. Add the capacity of the largest hose for one hydrant (1000 to 1500 gpm).
The sum is the governing case for the process plant.
In a tank farm, examine each storage tank. Select the potential fire incident with the largest capacity to use firewater. The firewater requirement for any incident is the sum of:
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All fire monitors which can reach the tank multiplied by the monitor design capacity) Plus the firewater for any fixed foam system on that tank
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Plus 0.33 multiplied by all fire monitors which can reach any of the adjacent tanks in one quadrant and within the greater of one tank diameter or 100 feet
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Plus the capacity of the largest hose for one hydrant (1000-1500 gpm)
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Plus the capacity or any monitors and water spray systems covering adjacent pump rows. The incident with the largest capacity is the governing case for the tank farm.
In an LPG storage area, examine each sphere. Select the potential incident with the largest capacity to use firewater. The firewater requirement for any incident is the sum of:
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All fire monitors which can reach the sphere multiplied by the monitor design capacity
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Plus the total deluge system capacity for the sphere
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Plus the capacity of one fire monitor for each of up to two adjacent spheres within 100 ft and within one quadrant
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Plus the capacity of the deluge or water spray systems for each of up to two adjacent spheres within 100 ft and one quadrant (50% of the deluge capacity if the deluge system is zoned for four or more sections)
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Plus the capacity of the largest hose for one hydrant (1000 to 1500 gpm)

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF Plus any allowance for sphere flooding
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Plus the capacity of any monitors and water spray systems covering adjacent pump rows
The incident with the largest capacity is the governing case for the LPG storage area.
For any residential, office, non-chemical warehouse, laboratory, etc. building the governing case for the incident is the sum of the capacity of the largest water sprinkler system plus two 250-gpm hoses.
For chemical warehouses, the governing case is the sum of the capacity of the largest water sprinkler system plus 2000 gpm for hydrants Fire Water Pump, Storage, and Piping Design
3.3.1 Fire Water Pumps
The Fire Water System capacity should beset at the largest of the governing cases plus an allowance of 10 to 20% for wastage. This value sets the minimum Fire Water pumping design capacity.
3.3.2 Fire Water Storage
The selected Fire Water pumping capacity is multiplied by the maximum expected duration of afire incident. This is usually four hours, but can be as much as six hours for process plants with large fuel quantities at pressures above 1000 psig or for warehouses with large quantities of flammable solid hydrocarbons such as polyethylene film or pellets. Add 50% if the storage replenishment system cannot supply at least half the firewater pumping capacity and if there are no backup firewater systems (utility water storage, BFW storage, cooling water storage, clean wastewater storage, etc. This value sets the usable firewater storage volume Fire Water Piping
Above-grade piping is generally carbon steel with an appropriate corrosion factor and minimum design conditions of 150 psig @
140 F. Such piping is usually used around the Fire Water Pumps.

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF It is rarely used inside fire hazardous zones except as risers to sprinkler and deluge systems or elevated fire monitors, or foam distribution systems. When used inside or above fire hazardous areas, it should be secured to resist blasts. Most of the firewater distribution system is below-grade. It is referred to as the Ring Main because it is arranged (and isolation valves provided) to assure that firewater can reach any fire hazardous area even if one section of the distribution pipe is out of service. Minimum design conditions are usually 150 psig @ 100 F. The Fire Water Ring Main piping is sized based on the following criteria:
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Given the loss of any single segment of the firewater ring mains, the system shall deliver at least 100% of the required delivery flow rate to any Fire Fighting Zone at a minimum pressure of 100 psig. At least one Fire Fighting Zone will have a required flow rate equal to the calculated governing case other zones may have lower required flow rates.
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Pressure drop is determined using the Hazen-Williams formula. Ac factor of 100 is used for most materials. For
HDPE, ac factor of 140 to 150 is used.
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Pipe lengths are estimated per Reference 25 - PTD-DGS-130 Guidelines For Hydraulic Circuits) plus a safety factor of Hydraulics are calculated for the highest flow rates and the greatest pipe distances and the worst consequences of single line segment failure. This may result in the addition of isolation valves or addition of afire waterline connection. Given the loss of any single segment of the firewater ring mains, the maximum velocity in any remaining segment shall not exceed 10 to 11.5 ft./sec for 60% of the required flow rate.
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Branches are sized such that the maximum velocity through the branch is less than 10 ft/sec for the larger of the sum of the fire monitors sprinkler systems/hose stations or the maximum flow to one fire hydrant.
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Design Allowances are not applied unless requested by the client in order to allow for future additions.

FIRE PROTECTION PHILOSOPHY AND DESIGN GUIDE
PROCEDURE NO.
PTD-DGS-133
REV
0
DATE
Nov. 11, PAGE OF 50

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