West texas

WEST TEXAS EXPLOSION

DETONATION SIGNATURES

EQUIVALENT TNT ESTIMATION: 7 Tons

20 to 30 TONS OF FERTILIZER BLAST : 6 Tons SEISMIC : 7 Tons CRATER : 8 Tons FRAGMENTS : ? (no data) BLAST SPEED : ? (no accurate data)

UPDATED DRAFT, FEW OFFICIAL DATAS AVAILABLE

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WEST TEXAS EXPLOSIONABOUT THE WRITER

I AM A RETIRED SAFETY ENGINEER WHO WORKED FOR MATRA / AEROSPATIALE MISSILES, NOW MBDA.I SPENT SOME 3000HOURS WORKING ON THE AZF CASE IN FRANCE. THE CAUSE OF THE STORED « AN » DETONATION REMAINS A MYSTERY EVEN 11 YEARS LATER .SOME 100MILLION DOLLARS HAVE BEEN SPENT IN STUDIES ,TRIALS AND LAWYERS, TO NO AVAIL.MY TOOLS ARE BASED ON DDESB, ISSUED / RECOMENDED SOFTWARES , DOCUMENTS, METHODS.THE PURPOSE OF THIS STUDY IS NOT TO CRITISIZE THE HUGE WORK DONE , BUT TO LOOK FROM A DIFFERENT VIEWPOINT.THIS DOCUMENT IS AN OPPORTUNITY FOR YOU TO USE METRIC UNITS!

UPDATED DRAFT, FEW OFFICIAL DATAS AVAILABLE

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WEST TEXAS EXPLOSION 28 to 34 TONS OF FERTILIZER INVOLVED IN THE DETONATION => 10% UNCERTAINITY. EQUIVALENT TNT ESTIMATION: 15000Lbs (6750Kg) to 20000Lbs (9000Kg) => 15% UNCERTAINITY. CRATER DIMENSIONS 93ft (28m)DIAMETER AND 10ft (3m) DEEP. TOTAL STORED 150 Tons OF AN:• 50Tons « AN » STORED IN WOODDEN BINS• 100 tons OF « AN » INVOLVED IN FIRE, NOT IN EXPLOSION. 18 MINUTES OF FIRE, »AN » CONSUMED OF THE 50Tons? FIRE INITIATION UNKNOWN EITHER ELECTRICAL PROBLEM (120V AC GOLF CART BATTERIES) OR ARSON, FURTHEST FRAGMENT RECOVERED , 2.5miles (4Km) BRAKE PAD OF THE GOLF CART.

PRELIMINARY INVESTIGATION, OFFICIAL RELEASE May 16, 2013


1.COMMENTS ON THE OFFICIAL RELEASE:

BLAST SIGNATURES LEAD FIRST TO AN EQUIVALENT TNT STRENGTH.BASED ON AN APPROXIMATE EQUIVALENCY COEFFICIENT, THE AVERAGED TNT LEADS TO THE FERTILIZER QUANTITY INVOLVED.IN THE OFFICIAL STATEMENT THIS PROCESS IS REVERSED: ACCURATE QUANTITY OF FERTILIZER: 30Tons, 10% UNCERTAINITY, LESS ACCURATE EQUIVALENT TNT: 7.8Tons, 15% UNCERTAINITY.THE ONLY EXPLANATION IS THAT, INVESTIGATORS KNOW BETTER THE FERTILIZER QUANTITY INVOLVED IN THIS TRAGIC EVENT.IF THIS IS TRUE, BASED ON THE OFFICIAL MINIMUM 28Tons, THE EQUIVALENT TNT SHOULD BE > 9Tons, »AN » / TNT USUAL EQUIVALENCY FACTOR RANGES FROM 0.33 UP TO 0.45 (ANFO 0.85).THAT FINALLY MEANS THAT INVESTIGATORS, WITHOUT SAYING, ESTIMATE THAT PART OF THE 30Tons FERTILIZER ONLY DEFLAGRATED.



BASED ON INVESTIGATORS ESTIMATION , APPROXIMATELY 30 Tons OF « AN » DETONATED. SINCE THE DENSITY OF « AN » IS IN THE RANGE OF 900KG/m3 AND TAKING INTO ACCOUNT THE BINS AND VOIDS,ONE CAN ESTIMATE THE EQUIVALENT STORAGE VOLUME AT 36m3.A FURTHER ESTIMATION LEADS TO A STACK ≈ 6 x 3 x 2m HIGH.IF END INITIATED , THE MAXIMUM DISTANCE IS 6m.WITH A DETONATION SPEED FOR « AN » OF 3500m/s THE EXPLOSIVE EVENT TAKES ≈ 2ms TO COMPLETE.IF THE INITIAL STACK WAS 50Tons ,THE DIMENSIONS COULD HAVE BEEN 6 x 4 x 2.5m => INITIAL SURFACE EXPOSED TO FIRE ≈75m2.UNLIKE AZF, NO WHITE BLANKET THROWN OUT, THEREFORE ONE CAN ASSUME THAT THE 50Tons ,EITHER BURNT,DEFLAGRATED OR DETONATED.

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IF THERE HAS BEEN A DEFLAGRATION OF A SIGNIFICATIVE AMOUNT OF FERTILIZER , SUCH EVENT MUST BE SEEN ON AIR SLAPS DURATIONS,MEASURED ON SEISMIC RECORDERS (close to the epicenter).DEFLAGRATION IS LESS STRONG THAN DETONATION BUT LASTS LONGER.

NEVERTHELESS THE TNT AVERAGE ESTIMATION OF 7.8 Tons SEEMS IN ACCORDANCE WITH THE DETONATION SIGNATURES .I RAISE DOUBTS ABOUT THE FERTILIZER INVOLVED, THE AVERAGE OF 30Tons SEEMS A LITTLE HIGH BUT HAS NO IMPACT ON THE ONGOING INVESTIGATION.

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TO BE NOTED:• IN MANY MAJOR ACCIDENTS THERE IS A REPORT OF A PRELIMINARY SMALL FIRST EXPLOSION. IF THIS FIRST EXPLOSION IS ONLY ms APART ONE CANNOT DISSOCIATE THE TWO EVENTS.MOREOVER « AN » HAS A DETONATION SPEED OF ONLY 3500m/sA LARGE VOLUME OF « AN » TAKES SOME ms TO DETONATE.I AM NOT SURE THAT FOR SUCH EVENTS THERE REALLY WAS A FIRST DETONATION, I THINK WHAT IS HEARD IS A PRECURSOR OF THE ONLY ONE MAIN EVENT.

• AN URGENT MESSAGE MUST BE SENT TO FIRST RESPONDERS,• HAZARDOUS PLANTS MUST QUICKLY REVIEW THEIR WORST CASE AND RELATED SAFETY ZONES.

PRELIMINARY INVESTIGATION, OFFICIAL RELEASE may 16, 2013 V.2

WEST TEXAS EXPLOSION COMPARISON WITH SMALLER EVENT : ROMANIA

MIHAILESTI , TRUCK ACCIDENT, HAS A SLIGHTLY SMALLER CRATER VOLUME AND SEISMIC MAGNITUDE .HERE ALSO AN INITIAL FIRE WAS THE TRIGGER.ESTIMATED STRENGTH 5 Tons OF TNT, 10Tons OF FERTILIZER(HIGH NITROGEN CONTENT).

Air slapSeismic

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WEST TEXAS EXPLOSION COMPARISON WITH BIGGER EVENT : AZF

AZF IS A TEN TIMES STRONGER EVENT, MAGNITUDE 3.3 AND CRATER 8800m3. THE IMMEDIATE DETONATION HAS RELEASED A HUGE QUANTITY OF « AN » PRILLS IN THE SURROUNDINGS (WHITE BLANKET). STRENGTH ESTIMATED 80 Tons OF TNT (200Tons OF FERTILIZER. DETONATION INITIATION UNKNOWN.

OMP SEISMIC DATA

CRATER,BLDG OUTLINE

AMMONITRATE BLANKET

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WEST TEXAS EXPLOSION COMPARISON WITH MUCH BIGGER EVENT : OPPAU / RYONGCHON

OPPAU IN 1921 AND RYONGCHON IN 2004 INVOLVED AN EQUIVALENT TNT APPROX. 1KT AND 0.8KT RESPECTIVELY.CRATERS WERE 80000m3 AND 60000m3 , OPPAU WAS AT 0m GROUND LEVEL (BURIED BLDG) TO THE CONTRARY OF RYONCHON + 1.5m. MAGNITUDES ESTIMATED 3.7 AND 3.5

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WEST EQUIVALENT TNT ESTIMATION: BLAST => 5 TO 7 TONS

MOST ENERGY GOES INTO THE BLAST AND CRATER, WEAK BUILDING ,WEAKENED EVEN MORE BY THE FIRE, ONLY SECONDARY FRAGMENTS.

DENTED ULLAGE > 3bars

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BLAST SIGNATURES BUNCEFIELD EXEMPLE

UNRECOGNIZABLE > 8 barsDESTRUCTION > 2barsHEAVILY DAMAGED ≈ 0.5 barsCARRIAGE DENTED ≈ 0.15 bars

RAPID DECLINE OF BLAST PRESSURE BUNCEFIELD , VCE

EDGE OF GAS CLOUD

SIDE ON , 0.4bar 10ms

BUNCEFIELD VALIDATION TESTS WITH HIGH EXPLOSIVE (HE)

SIDE ON , 0.25bar 10ms

CAUTIONPRESSURE / IMPULSECURVES DIFFER BETWEEN VCE AND HE.

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BUNCEFIELD EXPLOSION

MECHANISM, HSE DOC.

FOR COMPARISON ONLY VCE IS NOT A POINT

DETONATION.

A VCE EPICENTER CAN REACH SEVERAL

100 METERS.

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WEST BLAST PRESSURE FOR 7 TONS OF TNT BECV4.3.

100mbar 250m

50 mbar 450m

10 mbar 1400m

2mbar = strong sonic bang

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WEST EQUIVALENT TNT ESTIMATION: SEISMIC ML 2.1=> 7 TONS

DIFFERENT STUDIES HAVE SHOWN THE RELATION BETWEEN MAGNITUDE AND DETONATION STRENGTH.THE MAXIMUM MAGNITUDE ACHIEVED FOR WELL GROUND COUPLED EXPLOSIVES IS M = 0.73*Log (WKg) + 0.26 (Khalturin).BASED ON THIS STUDY, CORROBORATED BY OTHERS WITH SOME MINOR VARIATIONS ONE CAN GIVE A MORE COMPLETE FORMULA INCORPORATIONG THE GROUND COUPLING COEFFICIENT.A SURFACE DETONATION HAS A GROUND COUPLING FACTOR OF 0.14 (CONWEP), FACTOR WHICH CAN REACH 0.2 FOR EXPLOSIVES LYING DIRECTLY ON THE GROUND OR ON A CONCRETE SLAB.

M = 0.73*Log(WKg) + Log (fcoupling) + 0.26 + Gsoil deficit

2.1 – Log(0.2) = 0.73*Log(WKg) = 2.8 => WKg = 6850KgNote: The « + 0.26 » in Khalturin formula is neglected, balanced by an estimated deficit G= - 0.26 for standard soils.

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EQUIVALENT TNT ESTIMATION: CRATER => 9 TONS

FOR SURFACE DETONATIONS A SIMPLE APPROXIMATION OF THEEQUIVALENT TNT IS W Kg = 10*Vm3 WITH V THE CRATER VOLUME. THIS SIMPLIFIED FORMULA IS VALID FOR ALLUVIUM BUT DOES NOT TAKE INTO ACCOUNT THE PRECISE SOIL TYPE.THE CRATER IS 28m WIDE AND 3m DEEP => VOLUME ≈ 900m3.A VOLUME CHECK CAN BE MADE WITH THE MAGNITUDE SINCEFOR SURFACE DETONATIONS, BOTH ARE CLOSELY RELATED BYM = 0.73*Log( Vm3) => M = 0.73*Log(900) = 2.1 OK=> WKg = 10*900 = 9Tons.

THE CALCULATION BASED ON CONWEP, SEE NEXT SLIDE,GIVES FOR SUCH CRATER 7000KG.

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EQUIVALENT TNT ESTIMATION: CRATER => 7 TONS

BASED ON AZF EXPERIENCE WE USE ASPHALT INSTEAD OF CONCRETE SINCE THE CONCRETE IN CONTACT WITH AMMONITRATES IS SERIOUSLY DAMAGED AND WEAKENED.THE RANGE FOR WINDOWS BREAKAGE CONSIDERS A RANGE WHEREALMOST ALL THE WINDOWS ARE BROKEN.BY EXPERIENCE THIS RANGE IS DOUBLED FOR 5% WINDOWS BROKEN,USUALLY DUE TO REFLECTED WAVE.

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EQUIVALENT TNT ESTIMATION: FRAGMENTS => ?

A REMARQUABLE FRAGMENT HAS BEEN FOUND 2.5miles FAR (4Km) !IT IS THE BREAK PAD OF THE GOLF CART.DUE TO THIS EXEPTIONAL PERFORMANCE ONE CAN ASSUME: AN OPTIMAL EJECTION ANGLE BETWEEN 20° AND 25°, A SMALL DRAG COEFFICIENT < 1.2 A STABLE TRAJECTORY, AN EJECTION SPEED >1000m/s, A HEAVY METALLIC FRAGMENT > 0.8Kg, A BLAST IMPULSE > 1bar*s A DISTANCE TO THE EXPLOSION EPICENTER < 3m.

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22°

1000m/s

EQUIVALENT TNT ESTIMATION: BLAST OVERSPEED => ?

BASED ON THE AIR SLAP ARRIVAL TIME AT A NEARBY SEISMOMETER ONE CAN ESTIMATE THE BLAST STRENGTH.MEASURE THE ARRIVAL TIME OF THIS AIR SLAP.EXTRACT THE OVERSPEED BY USING THE PRECISE, STANDARD SOUND WAVE SPEED AT EVENT TIME (TEMPERATURE, HYGROMETRY AND WIND CORRECTED).

THE SOUND OVERSPEED IS RELATED TO THE TNT EQUIVALENT BY OVERSPEED ΔV m/s = (1100 / Dr), SCALED RANGE Dr = Dm / WKg0.33 OR WKg = (ΔV *D/1100)3, FORMULA CORRECT FOR 50 < Dr < 400 (See Empirical Scaling Laws for Truck Bomb Explosion by K. Koper and Al).

FOR AZF THIS FORMULA GAVE ΔV m/s = 349.5 + 4.1Wind - 342.7 = 10.9m/s AT 4190m => WKg = (10.9*4190 /1100)3 = 72000Kg TNT.

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EQUIVALENT TNT ESTIMATION: BLAST OVERSPEED => ?

METEOROLOGICAL DATAS ARE ESTIMATED: T = 27°C , WIND 8m/s SE.BLAST SPEED TO WHTX = 356.5m/s – 7.9m/s = 348.6m/s WIND CORRECTED.SOUND SPEED ESTIMATED 348.0m/s => ARRIVAL TIME DIFFERENCE BLAST – SOUND = 39860(1/348 -1/348.6) = 0.2s.THIS TIME DIFFERENCE IS WHAT WAS EXPECTED FOR 7.5Tons OF TNT. PROBLEM IS, ALL DATAS ARE ESTIMATED AND WHTX IS TOO FAR TO PROVIDE ACCURATE RESULTS, FOR MORE THAN 98% OF THE DISTANCE BLAST AND SOUND TRAVEL AT THE SAME SPEED.

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39860m

WHTXN

60°WIND 7.9m/s

111.8s

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