Which Foam to Choose for Hydrocarbon Tank Fires
AFFF Weakness - Fire Crew Safety
foam blanket stability, burnback rate, and wicking action modify the relative degree of efficiency of AFFF on open spill fires The AFFF blanket should not be relied on to be permanent and should be renewed from time to time as the rescue operation proceeds Source: NFPA 403 (1978)
The effect of heat on film formation
At high temperature film formation will not take place on most hydrocarbons
Spreading coefficient
Film
n octane
aviation gasoline
No film
Temperature 0C
Source: US Naval Weapons Research Department
Storage Tank Fire Fighting
No longer shallow spill fire Been burning for several hours before foam attack Fuel volatile and very hot (~400deg C) Needs a foam with Good bubble quality Resistance to flame attack Resistance to radiated heat Good edge sealing against tank shell Good cooling effect Good post fire security - no flashbacks! = Modern FP/AR foams
AFFF difficulties on tank fires
AFFFs shown to struggle on many tanks
no film formation fast drainage & poor heat resistance
Detergent base emulsifies with hydrocarbons
emulsifies with fuel when applied forcefully causes flashbacks and re-ignition risk
AR-AFFFs are also used on tanks but:
polymer needed for polar solvents only thicker concentrates can give proportioning difficulties expensive option (2-3x cost FP!)
FP is designed for tank fires
Most SERIOUS fires are large and deep seated (tank fires) Good quality FP foam benefits: slow draining foam cools hot fuel seals well against hot metal shell no emulsification with fuel proven performance on tank fires no thick polymers resists severe flame attack (strong protein bubbles) excellent post-fire security reliability, no flashbacks cost -effective Foam tests help assess suitable products UL 162 (ability & system integrity) Lastfire (representative)
Detergent-free Fuel repellant Protein skeletal structure - Resistance to heat - Edge sealing - Cooling effect Post-fire security Most COST-EFFECTIVE protection
Major users: Exxon -Mobil, BP, Shell, Caltex
Formerly marketed as FP70 Plus
Applications:
Hydrocarbons 100% MTBE Unleaded Gasolines (20% MTBE) Semi-asp & Asp. Monitors Top Pourers Rimseal Pourers Base Injection MEX Bund Pourers Foam sprinklers
Performance Characteristics
AFFF Typical Application Knockdown Burnback Resistance Fuel Tolerance
The more the better!
FP
FFFP
ARAFFF
ARFFFP
Aviation Oil Tanks
MultiAviation Multipurpose purpose
2 Foam tests help assess products for tank fires
Why is
important?
totally independent test house comprehensive UL 162 standard no profit motive charge manufacturers for testing every product tested by foam specialists follow up service monitors quality over time ensures consistent product supplied all listings shown at www.ul.com Poor products FAIL!
Key Global OPC approval!
LASTFIRE Tank Test
Good Test NEEDS: Large fire area (~ 5 m2) Long preburn ( ~ 3 mins) Deep fuel layer (> 6 cm) Large qty (~ 300 litres) Tall wall height (~ 50 cm) With metal obstructions Fixed specification volatile fuel Foam quality matches real equipment (semi-aspirated monitor, aspirated monitor and fixed pourer nozzles)
= Representative!
BP, Shell, Exxon-Mobil, MOL, Total-Fina-Elf, Chevron - Texaco, Repsol, Saudi Aramco etc.
LASTFIRE test
Extinction within 7 mins Excellent burnback resistance
FP
10 12
23 25 30 mins Rapid Knockdown but Poor Sealing Capability
Preburn Foam Application
Torch tests
Burnback
AFFF
LASTFIRE test results
15
Burnback Resistance
Fire Control
Maximum 300 points, 100 available for each 3 stages of LASTFIRE TEST
7.5
Vapour Suppression (torch test 2)
7.5
Vapour Suppression (torch test 1)
Extinguishment
65
Total: 100
End users relative importance of LASTFIRE Test fire performance criteria
(Developed from poll of end users)
Post-fire security crucial!
Aspirated applications = best results Foam needs to control/prevent edge flickers and resist re-ignition Post-fire security is very important
Foams that suddenly flashback can be dangerous to firefighters! More common with AFFFs/ AR-AFFFs More common during semi-aspirated applications AFFF
ANGUS FIRE FOAMS: LASTFIRE TESTED
Reduced fire performance Semi-Aspirated Nozzle FP70 32.5% Aspirated Nozzle FP 70 72% Angus Tankmaster 72% Tridol ATF3-6 77% Acceptable fire performance Good fire performance Tridol ATF3-3 95% Tridol ATF 1-3 90% Tankmaster 100% Tridol ATF3-3 100% Tridol ATF1-3 95% Tridol ATF 3-6 92.5% Tankmaster 100% FP 70 100% Tridol ATF 3-6 92.5% Tridol ATF 1-3 90%
Total Scores: ATF1-3 FP70 Plus ATF3-3 ATF3-6 FP70 275 272 265 264.5 202
System Nozzle Tridol ATF 3-3 70%
25%
50%
80%
100%
Environmental Issues
Comprehensive Data - mild effect only on fish & aquatic organisms Rainbow trout LC50 (48 hrs) for TANKMASTER >10,000ppm 10,000 ppm = 1% foam solution Protein base = Lowest Environmental Impact UK Environment Agency Advice - Avoid Detergents NB - the higher the ppm number the more you can use before bad effects!
Environment: Improved WWTP
AFFF fire fighting foam significantly disrupted a refinerys wastewater treatment plant (WWTP).
Source: Industrial Fire Safety, Nov/Dec 92
FP foams like less disruptive Also readily biodegradeable
are far
Natural protein base (FP) more easily digested by bacteria Can use more before any problem
AFFF Toxicity - Detergent
Detergent is the most acutely toxic of the main foam constituents
Source: UK Environment Agency
24 Hour LC50 < 20 mg l-1
Oil / Water Separators
Foams that contain detergent can mix with the fuel itself and carry it into the water environment, giving rise to much higher oxygen demands in the water
Source: UK Institution of Water & Environmental Management
The only solution for fire fighters is to avoid the use of foams that contain detergent.
Source: UK National Environmental Technology Centre
Proven Emergency Response
Repsol S. Spain - Aug. 03 Antonov - 100kL Trucks - non-stop 2 drivers ea. Wide range products incl. Alcoseal, Niagara & Tridol ATF Idemitsu, Japan- Sept. 03 Boeing 747 - 60kL Alcoseal & ATF3-6 Atas Refinery, Turkey- Mar 04 A 300 Airbus - 42kL FP70 100kL replenishment
Comprehensive Foam Service
24hr/365 days Emergency Service Bulk emergency stocks Technical support - Foam/Equipment Full range Portable & Fixed Eqpt. Full Foam Testing Service Your Partners in Protection!
ALL OPTIONS COVERED
T! OS IT M
YO EN WH
ED NE U
Atas Refinery Tank Fire, Turkey - July 2004
