Charge weight

Once the equivalent charge weight of TNT is estimated, the blast peak overpressures in the field can be found by applying this charge weight to the scaled distance in the blast chart (Figure 4.18). 

The equivalent charge weight of TNT is calculated on the basis of the entire cloud content. FMRC recommends that a material-dependent yield factor be applied. Three types of material are distinguished Class I (relatively nonreactive materials such as propane, butane, and ordinary flammable liquids) Class II (moderately reactive materials such as ethylene, diethyl ether, and acrolein) and Class III (highly reactive materials such as acetylene). These classes were developed based on the work of Lewis (1980). Energy-based TNT equivalencies assigned to these classes are as follows ... 

The blast originating from a hemispherical fuel-air charge is more like a gas explosion blast in wave amplitude, shape, and duration. Unlike TNT blast, blast effects from gas explosions are not determined by a charge weight or size only. In addition, an initial blast strength of the blast must be specified. The initial strength of a gas-explosion blast is variable and depends on intensity of the combustion process in the gas explosion in question. 

In the HSE method, the equivalent-charge weight of TNT is related to the total quantity of fuel in the cloud it can be determined according to the following stepwise procedure ... 

The equivalent charge weight of TNT can now be calculated using Eq. (7.2) as follows ... 

Blast effects. Once the equivalent charge weight of TNT in kilograms has been determined, the side-on peak overpressure of the blast wave at some distance R from the charge can be found with Eq. (7.3) ... 

WTien accounting for effective charge weight at ground reflection the conversion is [49] ... 

W,. = effective charge weight in pounds of TNT for estimating surface burst effects with free air. 

Compare two different explosive charge weights of the same material. For an observed overpressure of 40 psi from a specific charge using the scaling equation above, the scaled distance is Z = 5 ft/lb /. WTiat is the distance for an overpressure of 40 psi with a charge of 500 lb ... 

W = required vapor capacity in pounds per hour, or any flow rate in pounds per hour, vapor relief rate to flare stack, Ibs/hr W(. = charge weight of explosive, lb Wj. = effective charge weight, pounds of TNT for estimating surface burst effects in free air W, = required steam capacity flow or rate in pounds per hour, or other flow rate, Ib/hr Whe = hydrocarbon to be flared, Ibs/hr Wtnt equivalent charge weight of TNT, lb Wl = liquid flow rate, gal per min (gpm)... 

Required to Maintain Constant Velocity for Constant Charge Weight for Constant Charge Weight... 

Test Weight of Charge, Weight of Charge, Detonator 90/10 MF/K chlorate PETN/LA... 

Start up/load charge weighted mean iron mg/kg Fe 0.1 max. 

In the initial stage the amount of fines consumed per unit charge weight depends only on the total number of drum revolutions, independent of the rotational speed (12, M6). The disappearance rate per unit charge weight and per drum revolution of the fines varies directly with seed density, the... 

Five shots are fired of the maximum permitted charge weight of explosive into methane/air mixture in Break test I. No ignitions may occur. 

When detonating cord is not required directly to initiate high explosives, but solely to transmit detonation from one place to another, it is sometimes an advantage to use a cord with a very low charge weight. Two types of such cord are at present available in certain countries. 

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