WJH FAA Technical Center John W. Reinhardt Fire Safety Section, AAR-440 Atlantic City Int’l Airport, New Jersey 08405 609.485.5034

WJH FAA Technical CenterJohn W. Reinhardt Fire Safety Section, AAR-440 Atlantic City Int’l Airport, New Jersey 08405609.485.5034

• OBJECTIVE• TECHNICAL APPROACH• RESULTS

NFPA 750Water Collection Tests

• OBSERVATIONS

OBJECTIVES

To determine the critical parameters required to scale a water mist system combined with nitrogen, used as an aircraft cargo compartment fire suppression system that have met the MPS.

CONSIDERATION

The scaling consideration of the water mist/N2 fire extinguishing system is for cargo compartments of volume sizes of 719 ft3 (298 in x 125 in x 42 in) and 6252 ft3 (590 in x 164 in x 80 in).

SCALING APPROACH

• Characterize the WMS system that passed the MPS tests using the NFPA 750 standard.

• Characterize nitrogen system.

• Use defined system parameters and transpose them to different scale cargo compartment, paying close attention to the vertical plane (z-axis). Adjust system as needed in scaled compartment to provide same critical parameters values.

CHARACTERIZATION OF WATER MIST (CONT.)

• Water collection (mass flow) on a 18” by 18” pan located on the fire zone at 36” above the cargo compartment floor in order to determine the amount of water wetting the defined combustible surface.

ADOPT NFPA 750 – STANDARD ON WATER MIST

FIRE PROTECTION SYSTEMS

This NFPA document was prepared by the Technical Committee on Water Mist Fire Suppression Systems and acted on by the National Fire Protection Association, Inc. on November 1999. It was issued by the Standards Council on January 2000, with an effective date of February 11, 2000

In developing this standard, the committee addressed system components and hardware, system types, installation requirements, design objectives, hazard classifications, calculations, water supplies, atomizing media, plans, documentation, acceptance criteria, and maintenance considerations

NFPA 750 represents a significant advancement in water mist technology and the knowledge base associated with its application.

CHARACTERIZATION OF WATER MIST

NFPA 750 Section A-5-2 (Appendix A)

1. System Flow Rate

2. System Operating Pressure

3. General Water Requirements

4. Nozzle Characteristics

5. Nozzle Spray Characteristics

6. Nozzle Installation Parameters

7. Activation Device

8. General Design Parameters

NITROGEN MEASUREMENT

The measurement of the nitrogen volumetric concentration, in the scaled cargo compartment, will be achieved by determining the oxygen volumetric concentration in the hypoxic condition (using gas analyzers). The time to reach an inert condition with nitrogen will also be considered during the scaling of the system.

I. SYSTEM FIRE PERFORMANCE OBJECTIVE - Fire Suppression

II. WATER MIST SYSTEM (NFPA 750 – Standard on Water Mist Fire Protection Systems) – The Environmental Engineering Concepts water mist system was a balanced high-pressure, Class I system (i.e., at least 10% of the spray is less than 200 microns).

CHARACTERIZATION OF WATER MIST/N2 SYSTEM

II. WATER MIST SYSTEM (CONT.)

1. System Flow Rate (Minimum and Maximum)

a. Flow rate – from 0.54 gpm (1 zone activated) to 1.84 gpm (4 zones activated)

b. Flow rate per unit area – 0.343 lbs/min*ft2

2. System Operating Pressure (Minimum and Maximum)

a. Nozzle operating pressure range - from 550 psig (4 zones activated) to 1150 psig (1 zone activated).

b. Pump/cylinder operating pressure range – for pump model Giant P217A the inlet pressure is up to 90 psig and the discharge pressure is up to 2500 psig

c. Pump inlet and outlet pressure and flow rate requirements – the inlet pressure is from 20 (minimum) to 90 psig (maximum), the discharge pressure is up to 2500 psig (1250 psig used during the fire tests), the pump will produce a volume of up to 3.36 gpm.



3. General Water Requirements

a. Quantity/duration – 9 gallons (continuously discharging for 5 minutes)

b. Quality – Special consideration should be given to the quality of water that will flow through the water mist system. Water with total dissolved solids (DS) counts of greater than 500 parts per million (ppm) or water with high calcium carbonate levels or PH levels above 7.5 may not be satisfactory and could lead to excessive nozzle blockage and nozzle maintenance.

c. Temperature – Above freezing point, preferable at standard room temperature. The pump relies on the water running through it to keep it cool.

d. Pressure – Correct water pressure and supply rate is essential to the pumps operation. The water supply pressure must be maintained between a minimum of 20 psi and a maximum of 90 psi to operate the pump.



4. Nozzle Characteristics

a. Type(s)/model numbers – EEC/MicroCool nozzle, nozzle orifice is 0.0245" (0.63 mm) in diameter

b. Flow rate (minimum and maximum) – 0.0675 gpm to 0.23 gpm

c. Operating pressure (minimum and maximum) – 1025 psig to 1150 psig

5. Nozzle Spray Characteristics

a. Spray angle – 27º, nozzle pointing down vertically

b. Drop size distribution – Droplet sizes range from 70 to 100 microns (Class I), provided by manufacturer. No access to PDPA system

c. Momentum/velocity – 3.89 feet per second (obtained by using high speed film)



6. Nozzle Installation Parametersa. Distance above floor – 65" above floorb. Distance below ceiling - 1" below ceilingc. Distance above hazard – (i.) For bulk load test – 29" above hazard, (ii.)

For containerized test - 1" above hazard, (iii) For surface burn test - 11" above hazard(minimum and maximum), and (iv) for aerosol can explosion test - 41" above hazard.

d. Nozzle spacing - 16" between nozzles (8 nozzles per zone)e. Zone spacing - 30" between zonesf. Orientation – nozzles pointing down verticallyg. Minimum distance from walls and obstructions – Atomization nozzles

should never be pointed towards and allowed to spray on any close object or surface otherwise the fog will condense; a distance of 18" to 24" should be preserved. Use a nozzle plug to block off the fog if this cannot be avoided.



7. Activation Devicea. Type/model number – Manual activationb. Activation, temperature – 1 minute after ceiling temperature reached 200ºF

8. General Design Parameters

a. Pipe requirementi. Size – 3/8” diameter stainless steel tubing ii. Operating pressures – up to 2500 psig

b. Fittingsi. Type – compression fittings ii. Operating pressure – up to 2500 psig



8. General Design Parameters (Cont.)c. Pumps

i. Valves, fittings, and filters – drain valves, NPT type fittings (with swivel), twin filter components of 10 and 5-micron units ii. Power requirements – 120 Vac (Motor), 24 Vdc (Relays)iii. Operating pressure and flow rates – See Section 2.c System Operating Pressureiv. Water requirements – See Section 3. General Water Requirements


III. NITROGEN SYSTEM CRITICAL PARAMETERS

1. Cylinder valves and fittings – Two Matheson 3020 Series Regulators,

CGA 580, with a maximum inlet pressure of 3500 psig, and a flow rate of 89.3 CFM (at 500 psig) per regulator.

2. Cylinder capacity – 16 High Pressure Size T cylinders, 1.73 ft3 each

3. Cylinder operating pressures – 2500 psig

4. Volumetric Concentration – 90% N2 in air

5. Flow Rate – initial rate at 500 psig was 178.6 CFM (average = 154.7 CFM)

6. Time for Initial Protection – an average of 12.5 minutes

7. Fire/Explosion Protection Time – 180 minutes (infinite if OBIGSS system used)



TC-10 CARGO COMPARTMENT (2000 FT3)WMS/N2 INSTALLATION


Zone 1Zone 2Zone 3Zone 4Zone 5

Zone 6Zone 7Zone 8Zone 9Zone 10 Zone 11 Zone 12 Zone 13

T o p V ie w F r o n t V ie wF A A T C - 1 0 W a te r M is t / N 2 S e tu pJ . R e i n h a r d t8 A p r i l 2 0 0 3

16.0”30.0”

15.5”10.9”

164.0”66.0”

W a t e r M is t N o z z le

N i t r o g e nN o z z le( 4 )319.3” V o lu m e = 2 0 0 0 f t 3

80.0” (Typical) 8.0” A i r c r a f t C a r g oC o m p a r t m e n t

Zon

e 1

Zon

e 2

Zon

e 3

Zon

e 4

Zon

e 5

Zon

e 6

Zon

e 7

Zon

e 8

Zon

e 9

Zon

e 10

Zo

ne 1

1

Zon

e 12

Zon

e 1

3

Top View

Front View

FAA TC-10 Water M ist/N2 SetupJ. Reinhardt8 April 2003

16.0

”

30.0

”

15.5

”

10.9

”

164.0”

66.0”

Water M ist Nozzle

NitrogenNozzle

(4)

319.

3”

Volume = 2000 ft3

80.0

” (T

ypic

al)

8.0”

Aircraft CargoCom partm ent

27 degrees

TC-1013 Zones/95 Nozzles


B-737 CARGO COMPARTMENT (719 FT3)WMS/N2 INSTALLATION

CHARACTERIZATION OF WATER MIST/N2 SYSTEMTop View

Front V iew

298.0”

42.0”

B737 Water M ist/N2 SetupJ. Reinhardt

25 Septem ber 2003

Volum e = 719 ft 3

Zo

ne

1Z

one

2Z

one

3Z

one

4

Zo

ne

6Z

one

7Z

one

8Z

one

9

Zo

ne 1

0

3 9 .3 6 ” (1 meter)

18.34”

42.0”

S ide View

27 degrees

16.0”

125.0”

30.0”

N ozzle P lum e

125.0”

B-7379 Zones/72 Nozzles


B-777 CARGO COMPARTMENT (6252 FT3)WMS/N2 INSTALLATION


B-77725 Zones/180 Nozzles

Top View

Front V iew

B777-300 Water Mist/N2 SetupJ. Reinhardt

25 September 2003

164.0”

80.0”Volume = 6252 ft

3

Zon

e 1

Zon

e 2

Zon

e 3

Zon

e 4

Zon

e 5

Zon

e 6

Zon

e 7

Zon

e 8

Zon

e 9

Zo

ne 1

0

Zo

ne 1

1Z

one

12

Zon

e 13

Zo

ne 1

4Z

one

15

Zon

e 16

Zon

e 17

Zon

e 18

Zo

ne 1

9Z

one

20

Zo

ne 2

1Z

one

22

Zon

e 23

Zo

ne 2

4Z

one

25

590 .0”

27 degrees

N2 INERTING OF CARGO COMPARTMENTS

ITEM NO. DESCRIPTION CARGO VOLUME (FT3) INERT TIME (Min) REQUIRED NUMBER OF REGULATEDDISCHARGE RATE (CFM) DISCHARGE PORTS

1 TC-10 Lower Cargo Compartment 2000 12.5 160.0 22 B-737 Lower Cargo Compartment 719 12.5 57.5 13 B-777 Lower Cargo Compartment 6252 12.5 500.2 64 TC-10 Class E Cargo Compartment 8082.5 12.5 646.6 7

WATER COLLECTION TEST RESULTS

1. Placed 18”x18” pan on scale

2. Collected weight samples every 30 seconds

3. Collected samples for 5 minutes

4. Ran tests 10x per cargo size


Front V iew

Dc10 Water M ist/N2 SetupVolum e = 2000 ft

3

S ide View

Water Collection Pan

Cardboard Boxes

Water M istNozzle

Aircraft CargoCompartment 29.0”

WATER COLLECTION TEST TC-10

1 Zone/8 Nozzles On


WATER COLLECTION TEST

Front V iew

B737 Water M ist/N2 SetupVolume = 719 ft 3

S ide View

Water Collection PanCardboard BoxesWater M ist

Nozzle

Aircraft CargoCompartment

5.0”

B-7371 Zone/8 Nozzles On

Front V iew

B777 Water M ist/N2 SetupVolume = 6252 ft

3

S ide View

Water Collection PanCardboard Boxes

Water M istNozzle

Aircraft CargoCom partm ent

43.0”


WATER COLLECTION TEST B-777

1 Zone/8 Nozzles On


WATER COLLECTION TEST

Front V iew

Water Collection Pan

Cardboard Boxes

Water M istNozzle

Class E CargoCompartment

S ide View

90.5”

TC-10 Class E1 Zone/8 Nozzles On

WATER COLLECTION TESTS (Average)

0

0.5

1

1.5

2

2.5

3

3.5

4

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Time (Min)

We

igh

t (L

bs

) Test 100703T1

Test 100703T2

Test 100803T1

Test 100803T2

Test 101003T1

B737 - Pan 5 inches from Nozzle

DC10 - Pan 29 inches from Nozzle B777 - Pan 43 inches from Nozzle

DC10 Class E - Pan 90.5 inches from Nozzle


3.8 lbs

1.5 lbs

0.9 lb

1.4 lbs

1. The NFPA 750, Standard on Water Mist Fire Protection, provides an excellent guideline to characterize an aircraft cargo compartment water mist fire suppression system.

2. The water collection test provides a simple and inexpensive method to determine the amount of water available on the combustible surface. This water, accumulated on the surface, cools the burning surface and provides liquid for oxygen dilution during the fire suppression process. This test does not provide particle size distribution, flux density, nor spray momentum, but it offers a quick and an inexpensive way to compare the WMS/N2 system in various compartment sizes.

3. After performing the water collection test on the WMS/N2 system in the B-737 and B777, it was observed that the water accumulated in the pan was the same or was more than the water accumulated during the TC-10 test.

4. The above statement can not be made for the TC-10 Class E compartment. The amount of water accumulated on the combustible surface needs to be increased; this can be achieved by reconfiguring the installation or adding more zones.

Documents

WJH FAA Technical Center John W. Reinhardt Fire Safety Section, AAR-440 Atlantic City Int’l Airport, New Jersey 08405 609.485.5034