The design section provides an understanding of the characteristics of HFC-227ea in relation to its flow from its storage container, through the piping network, and discharge from the distribution nozzles. Information is also given for the “Authorities Having Jurisdiction” for approving the system installation. Systems shall be installed and maintained in accordance to the NFPA 2001 (latest edition) and this manual. The calculation method has been investigated for the specific types of pipes, fittings and pipe I.D. If the application does violate the limitations mentioned in this Chapter, there is a risk that the system will not supply the designated quantity of agent.
The flow of HFC-227ea through the discharge piping is a complex two-phase flow. The Unique Fire HFC-227ea Engineered Systems have been investigated and comply with the UL 2166 Test Standards for Clean Agents. The NFPA 2001 Standards shall be followed by the system designer. The latest edition of NFPA 2001 is available from National Fire Protection Association, Batterymarch Park, Quincy, MA-02269.
The Unique Fire HFC-227ea system is designed for total flooding applications to extinguish Class A, B and C type fires. It is important that every system is designed to provide the maximum extinguishing characteristics and that the limitations for total flooding are strictly followed.
3.2 Defining Scope of Protection
Before making any calculation, the following must be known. This will provide the design parameters to protect the hazard.
a) The Hazard Class: A, B, C.
Note: Class A fires are those, which involve ordinary combustible materials, such as wood, cloth, paper, rubber, plastics and other cellulose-type materials. Refer to the NFPA 2001 (Latest edition).
b) Power is to be effectively shut down prior to system discharge. If power cannot be shut down, the hazard should be classified as Class C.
c) The volumes, areas, measurements of the hazard that are used for Class A hazards are the same as for those of Class B and C hazards.
d) Based on the respective class of fire, the minimum design concentration by volume will be assigned as the followings. See Section 1.4 for more details.
NOTE:
1) The minimum design concentration for total flooding applications of HFC-227ea is 6.7% for Class A materials in accordance with NFPA 2001 (latest edition), unless a higher concentration is required for the specific hazard being protected.
2) Concentration is determined by fuel test using cup burner method. For details information, please see NFPA 2001 (latest edition) Annex B. Design concentration is determined by the highest cup burner extinguishment value of Class B fuel found within protected hazard. The minimum Class B design concentration shall be UL 8.7%.
3) The minimum design concentration for Class C hazards shall be the minimum extinguishing concentration for Class A with a safety feature of 1.35, the Minimum Design Concentration for Class C is 7%.
e) Electrically non-conductive fire-extinguishing media is of importance.
f) Pressure Adjustment: The design quantity of HFC-227ea agent shall be adjusted to compensate for ambient pressures that vary more than 3000 ft of elevation from standard sea level. The atmospheric correction factor is provided in Table 3-1.
g) The minimum and maximum ambient temperature in the volume being protected.
h) The minimum and maximum temperature at which the HFC-227ea cylinders shall be stored when systems are unbalanced and protection against different hazards are 60 oF and 80 oF respectively.
i) The exact internal dimensions of the hazard in terms of length, width, and height.
j) Will materials, stock, etc. that accrue on a daily basis affect the volume in any appreciable amounts?
k) If any air handling equipment(s) is assigned to the hazard, review the equipment’s capacity as to air changes per hour. The hold time of the agent after discharge must be taken into consideration.
l) When the calculation method is used for multiple hazards and the temperature of the cylinders varies ±10°F, there is a risk that the system will not supply the required quantity of fire-extinguishing agent.
When the system is discharged into the hazard enclosure, normal cracks and gaps under doorways shall not impact system performance. If there are openings in the hazard enclosure, they must be sealed. Doors and normal vents that are required in the enclosure must be closed prior to, or at the time of discharge. Doors or closures that normally swing to a closed position and are not held open, or will not be opened when the HFC-227ea is discharged, need no system generated mechanism to make them closed. Doors and closures including ventilation that is held open or operating must have devices installed to shut them off at the beginning or before system discharge. Doors should be closed and ventilation fans shut down prior to discharge.
3.3 Amount of Agent Required
The following is an example of a hazard with a three nozzles engineered system. The system is for the protection of equipment. Table 3-2 shows the amount in pounds per cubic foot of HFC-227ea required for a specific concentration at a specific temperature.
Table 3-2: Amount of HFC-227ea Clean Agent Required for a Specific Concentration at a Specific Time refer to page 67
The minimum amount of agent required is 197 lb. Therefore, one 250 lb cylinder filled to 197 lb of HFC-227ea shall be used.
In case of the design quantity of HFC-227ea agent shall be adjusted to compensate for ambient pressures that vary more than 3000 ft of elevation from standard sea level, the agent required is determined by the following formula: refer to page 69
3.4 Cylinder(s) Configurations
The following are configurations for cylinder use in the engineered design method:
a) Single hazard with one cylinder and its piping and nozzle system.
b) Single hazard with multiple cylinders, each with their own piping and nozzle system.
c) Single hazard with multiple cylinders discharging through a common piping and nozzle system.
d) Multiple hazards with one cylinder discharging through its piping and nozzle system.
e) Multiple hazards with multiple cylinders discharging through a common piping and nozzle system.
3.5 Manifold
When required by hazard size, multiple cylinders may be manifold together to feed the common piping network. Typical manifolds use threaded fittings (Figure 3-3), Victaulic fittings (Figure 3-4) and welded fittings. When installing Victaulic fittings manifold, only machined groove piping is to be used. Use one of these whenever manifold is required and follows the guidelines listed below and sample illustrations. refer to page 74
3.6 Flow Limitations
The HFC-227ea Flow Calculation Software UFI 4.00 will select the pipe sizes for each section in the piping network based on the HFC-227ea flow rate for each section. Otherwise, pipe sizes can be manually input into the program. When doing so, the selected pipe sizes must fall within a minimum and a maximum range of flow rates as shown in Table 3-4. refer to page 106
3.7 Tee Limitations
To obtain the most economical piping for a given hazard layout, tees are employed to branch the HFC-227ea flow to the various locations within the hazard or multiple hazards. The exit branches of the tees must be horizontal. The maximum and minimum percentage imbalances permitted are shown as follows. The system has been tested using Schedule 40 steel pipe and 300 lb. Class ASTM A-197 fittings. Details are provided in the HFC-227ea Flow Calculation Software Manual UFI 4.0.
• System maximum imbalance from a branch of a Bullhead Tee is 30 – 70 %.
• System minimum imbalance from a branch of a Bullhead Tee is 50 – 50 %.
• System minimum flow imbalance from the side outlet of a Thru Tee is 10 %.
• System maximum flow imbalance from the side outlet of a Thru Tee is 35%.
• Bullhead tees must have both outlets in the same horizontal plane.
• Side tee splits must have the inlet and both outlets in the same horizontal plane.
• Elbows before tee splits must be located at a minimum distance of 10 nominal pipe diameters upstream of the tee. The fittings are measured center to center.
• It is not allowed to increase pipe size/diameter in the downstream flow direction in a piping network.
• Tee splits must be spaced a minimum of 10 nominal pipe diameters apart, plus fittings, measured center to center. more info refer to page 109
3.8 Nozzles
3.8.1 Area Coverage
Nozzles shall be installed with the inlet of the nozzle perpendicular to the ceiling. When installing the 180o sidewall nozzle, the side holes of the pattern are to be parallel with the wall on which the nozzle is being installed. See Figures 3-37 and 3-38 for details.
All nozzles are rated for a maximum hazard height of 16 ft (Figure 3-39). If the hazard exceeds 16 ft in height, multiple tiers of nozzles must be used for each 16 ft increment of the height of enclosure.
The maximum area coverage per nozzle is 1600 ft2 (40 ft x 40 ft). The longest side length is 40 ft (maximum) (see Figure 3-37). This maximum length limitation applies for a range in hazard height from 1 ft (minimum) to 16 ft (maximum).
3.8.2 Application
The 180° sidewall nozzle shall be adjacent to a wall. The area coverage cannot be exceeded. Two 180˚ sidewall nozzles may be used at the center of the hazard. They may be applied back to back, providing area coverage of 3200 ft2 (40 ft x 80 ft). See Figure 3-37 for details.
The 180° sidewall nozzle may be installed from 2” to 12” down when referenced from the ceiling. When referencing the wall to the nozzle, the range of installation is from 0” to 12” off the wall. For the 180˚ sidewall nozzle reference, the centerline is between the top orifice and the bottom orifice. See Figure 3-38 for details.
The 360° central nozzle shall be installed at the center of the hazard. The area coverage cannot be exceeded. The nozzle may be installed from 2”to 12” down when referenced from the ceiling. See Figure 3-38 for details.
During nozzle installation, pipe supports shall be rated to support the dead weight of the piping and the thrust forces of the HFC-227ea discharge.
3.9 Unbalanced Systems
For unbalanced systems, one or more of the following conditions apply:
a) Unequal flow rates at one or more nozzles.
b) Unequal orifice areas in multiple nozzle systems.
c) Unequal pipe sizes and/or lengths of branch legs.
d) Odd number of nozzles.
e) Both Bull tees and Side/Thru tee applications are used. The tee exits must be in the horizontal plane.
CAUTION: Calculation is based on agent storage temperature of 70°F. Therefore, the operating/storage temperature of the container must be in the 60°F to 80°F range for a single unbalanced system protecting two or more separate hazards. If the container operating/storage temperature is outside this range, an insufficient quantity of agent may be discharged from one or more discharge nozzles.
3.10 Equivalent Length Data refer to page 115