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爆炸及相關名詞 PowerPoint PPT Presentation


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爆炸及相關名詞. Explosion: 因壓力驟增而導致容器或建築物斷裂,碎裂 Detonation 爆轟 : 燃燒區的擴散速度大於音速者 Deflagration 爆燃 : 燃燒區闊算速度小於音速者,由可燃液體,可燃氣體,或粉塵引起 Implosion: 因為真空,引起的往內爆炸的效果  氣體快速膨脹,產生震波 shock wave; 震波衝擊在物體上之壓力為過壓 overpressure. 侷限爆炸 confined explosion. 指發生在容器或建築物內部的爆炸

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爆炸及相關名詞

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  • Explosion:

  • Detonation:

  • Deflagration:

  • Implosion:

    shock wave; overpressure


Confined explosion

confined explosion

  • : (dP/dt)max V 1/3 = Kg for gases

  • (dP/dt)max V 1/3 = Kst for dusts

    (cubic law)1/3

  • Kg: bar.m/sec = 55 for ; 75 for

  • Kst = 27-98 for PVC; 58-130 for ; 108-174 for


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20


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  • (e.g. )

  • : () ; (at solid surface)

  • : turbulence ()


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CEP, 2008, March issue


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  • :

    *

    * ; 20-60 g/m3; 2 6 kg/m3

    *

    * ( esp. in a confined space)

  • Kst: St-0: Kst = 0; St-1: Kst = 1 200; St-2: Kst = 200-300; St-3: Kst = >300


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A few basic terminology


Some facts about dust explosion

Some facts about dust explosion

  • According to statistics from US: 1980 2005: total of 281 deadly dust explosions;(119 death & 718 injury)

  • Dust explosion often triggers other explosions

  • Engineering safeguards: rapid detection, suppression and mitigation systems

  • Some examples of engineering control: explosion relief venting;

  • dust collector most likely place of dust explosion cyclone, electrostatic precipitator, filter baghouse, etc); others: silo, mixer, hopper, grinder, etc.


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Source: CEP, 2008, March

Examples of engineering controls


Vapor cloud explosion

Vapor Cloud Explosion

  • VCE:

  • : (e.g. )

  • BLEVE: boiling liquid expanding vapor explosion

  • : (worst case: liquid flammable and toxic)


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BLEVE; : ; ; ;

No 8, 1993;


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  • : ()

  • : 18.5 Kpa 5%; 43.2 kPa 50% ; 114 kPa5%; 144 kPa50%

  • TNT: Ze = r/mTNT1/3 [Ze: scaling factor, ; r ; mTNT]


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14.4 (Clancey, 1972)

(psi)

0.03

0.04

(143 dB)

0.15

0.3

95%

0.5 ~ 1

0.7

1

1.3

2 ~ 3

RC

2.3

3

3 ~ 4

5

5 ~ 7

7

9

10

300


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  • :

  • We = [P1 V1/(-1)] [1 (P2/P1) (-1)/]

  • = Cp/Cv ; 1 and 2

  • :


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  • : (inerting); (ventilation);

  • : purging

  • : ; (explosion-proof)

  • suppression:

    venting

    containment


Inerting

Inerting

  • MOC

  • ()MOC:

    (a)

    (b)

    (c) purging

    (d)


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  • :


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  • :

    * zone 0

    * zone 1

    * zone 2

  • : ()()(MIE)

    : No.24, 1997.


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  • OSHA:

  • : (1) ; (2) (a) ; (b) ; (c) ;

  • : (1) 1 ft3/min; (2) (a); (b) 5 ft

  • * 37.8oC


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14.9

(1) (a)3000 ft2ft2 0.25 gpm

(b)3000 ft2ft2 0.35 gpm(c) 3000 ft23000ft2(2) (a)ft2 0.25 gpm (b)ft2 0.35 gpm (c)

(3)

(a)

(b) 8 ft

(c) 2 ft

(4)

(gpm) : 18 25 34 50 58

(psi) : 10 20 35 75 100

(5)

(6)

(7)() (a) 500 ~ 2000 gpm (b) 150 ft

(8) 150 ~ 250 ft 50 ft


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14.10 (Davenport, 1977)

(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)


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  • !! ()

  • (overpressure)blowdown

  • : (a) (b) (c) (d) [; ] (e) worst case scenario (f)


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  • :

  • : maximum allowable working pressure MAWP,

  • : 90% MAWP

  • : MAWP%MAWP

  • : % Ps

  • backpressure: Pb,

  • blow-down: %Ps

  • : 120% MAWP

  • :


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  • MAWP:

    * 120% -;

    * 116% -

    * 110% -

    * 105% -

    * 98% -

    * 92.5% - (100%blowdown)

    * 90% -


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  • : (a) ; (b) ; (c) ; (d) ; (e)


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*P1; R1; E1; D1

Crowl & Louvar


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  • ();

  • : (a) (); (b) (balanced bellows); (c) rupture disc; ()

  • : (a) relief valve; (b) safety valve ; (c) safety relief valve


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Crowl & Louvar


Sizing

Sizing

  • () ( gas, liquid or gas/liquid mixture)

  • : (a) ; (b) (: )

  • 25-30%


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:

  • A = [in2 psi 1/2/30.8 gpm] Qv/(Co Kv Kp Kb) {(/ref /(1.25Ps Pb)}

  • Qv: (gpm); Co discharge coefficient; Ps, Pb = ; Kv = ; Kp = (); Kb =

  • Re


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:

  • Qm = A Co {2 gc Pg}

  • Pg = ; Co discharge coefficient;

  • 50 dia. ()


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  • :

    *

    *

    *

    *

    *


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  • knockout drums: (or blowdown drum)

  • :

  • scrubber:

  • flare:

  • total containment system: (must be expensive)


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Crowl & Louvar


Suppression systems

Suppression Systems

  • CEP, 92(3), 22-31, 1996

  • : suppressor (),

  • : CFCsodium bicarbonate; magnesium phosphate

  • :


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(difficult!)


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