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- Is BlastWrap® a chemical or a physical barrier?
- Does BlastWrap® have to be in contact with the fireball to work?
- Will it still mitigate a blast wave if it's not in contact with a fireball?
- What if we use this as window shutters would it work then?
- How would you stop a mortar using BlastWrap®?
- Would BlastWrap® stop a bullet?
- Does BlastWrap® suppress blast energy?
- How heavy is BlastWrap®?
- Are there any toxicity issues?
- How is BlastWrap® fixed in place?
- How much BlastWrap® do I need?
- Will BlastWrap® work against all types of explosive events?
- How do you select the right quantities of the right BlastWrap® components?
- How are blast loads transmitted by BlastWrap®?
- How many steps does the transmitted load estimation process involve?
- Evaluating blast hazard mitigation:
- How does BlastWrap® work?
Is BlastWrap® a chemical or a physical barrier?
BlastWrap® is a physical barrier that is very lightweight and frangible that has been designed to drastically reduce blast pressure and impulse by irreversible processes (it is basically an energy sink). It has a non-toxic fire and flash suppressant element to deal with the fireball. In short, BlastWrap® is a very low-density blast effect mitigation material which can prevent sympathetic detonation, substantially reduce impulse, peak pressure, reflected pressure, quasi-static pressure in partially or fully confined environments and kill after burn and post-blast fires.
Does BlastWrap® have to be in contact with the fireball to work?
No. BlastWrap® works primarily on the shock wave that drives the blast. It will work equally well with blast from non-fireball sources (pressurized container bursts and shock tubes) as it will with high explosives. BlastWrap® will dramatically reduce pressures and impulse from a detonation hundreds of meters away.
Will it still mitigate a blast wave if it's not in contact with a fireball?
Absolutely, yes. BlastWrap® will also reduce or totally eliminate the fireball.
What if we use this as window shutters would it work then?
Yes. BlastWrap® will dramatically reduce the blast pressure on the window pane.
How would you stop a mortar using BlastWrap®?
Ideally BlastWrap® would be placed around the mortar at the point of detonation in which case it could be reasonably expected to contain all of the hazardous blast and fireball effects. The difficulty lies in getting the BlastWrap® to the point where the mortar falls. Our proposal is to place BlastWrap® around areas that we would wish to protect and this approach is valid for many explosive incidents. An important aspect of reducing explosive damage is preventing an in contact detonation with the structure that is being protected. To this end, trip screens that are intended to cause the mortar to detonate before it strikes the structure should be used where possible.
Would BlastWrap® stop a bullet?
No. BlastWrap® is not armor but it is often paired it up with a anti-ballistic material like Kevlar or nano fiber. It works to make Kevlar much more effective by reducing the peak local pressures and by keeping the hot detonation products out of the weave.
Does BlastWrap® suppress blast energy?
Yes, BlastWrap® does a terrific job in suppressing blast energy. BlastWrap® is NOT armor, but when used with armor, it significantly reduces blast pressures and impulse, kills post-blast fires and even reduces the kinetic energy in the frags of a mine. That means that for a given charge size the damage is reduced, or the amount of armor needed to handle a given size is reduced.
How heavy is BlastWrap®?
BlastWrap® is a lightweight blast mitigation solution and has a density of 4.95lb per cubic foot (0.09g./cc).
Are there any toxicity issues?
BlastWrap® is environmentally friendly and there are no know health issues associated with any of the materials that are used in the product.
How is BlastWrap® fixed in place?
Blastwrap® can be attached in a myriad of different ways. It's low density allows many simple fixing strategies to be employed such as double sided tape.
How much BlastWrap® do I need?
This will depend on the threat scenario, but generally most application will not require more than three inch thickness and it is important to remember that in many scenarios 100% surface coverage is not essential to ensure adequate protection.
Will BlastWrap® work against all types of explosive events?
Absolutely yes! BlastWrap® has been tested in all types of explosive events, such as:
- Military high explosive such as C4
- Commercial explosive such as dynamite
- Improvised explosive such as ammonium nitrate based mixes
- Low explosive such as black powder
- Fuel air explosions like methane, propane,
- Enhanced blast explosives
Excellent blast mitigation characteristics have been found in all of the above tests.
How do you select the right quantities of the right BlastWrap® components?
The process is simple. You first classify the nature or condition of the blast environment needing mitigation. You then determine the severity of anticipated blast environment. Using guidelines provided under the appropriate blast condition category, you can determine the appropriate filler and BlastWrap® thickness. The guidelines estimate mitigated blast effects when using BlastWrap® alone. If transmitted loads are unacceptably high, then proceed to select optional layers that will bring residual blast effect to allowable levels.
The conditions which are significant to BlastWrap® fall into one of the following three categories:
- Unconfined (outdoors or un-congested, well-ventilated spaces).
- Confined and partially-confined spaces with solid explosive blast
- Confined and partially-confined spaces with flammable fluid and dust explosions or fireball hazards.
Then you estimate the size of the structure or container, which needs protection, as well as the total vent area and the total enclosed space surface area, for confined blasts. You must also determine if a need exists to protect against multiple or repeated-blast exposures (see Step 3 below). The total BlastWrap® area requirement is then determined using the guidelines which are provided under the 1-2-3 blast environment subheadings listed above.
Requirements for ballistic armor, jets fire impingement protection, Impact Limiter layers, and other environment protective components are determined from service information (e. g. not by blast variables). Deciding upon the need for Impulse Absorber layers is based upon determining the allowable pressure-time loading that can be imposed on a structure, and comparing with impulse through BlastWrap® using appropriate guidelines.
How are blast loads transmitted by BlastWrap®?
To estimate the loads transmitted to a structure or system being protected by BlastWrap®, use guidelines for predicting transmitted and reflected values provided in the appropriate subsection for blast environment. If no overpressure can be transmitted to a structure, then a gas barrier layer is required that will withstand residual blast overpressure on the blast-exposed side. This gas-impervious layer must stand off from the weak structure being protected. PLEASE NOTE: TRANSMITTED BLAST OVERPRESSURE CAN BE REDUCED TO ZERO WITH A GAS-TIGHT BACK ("LEE SIDE") LAYER, BUT IMPULSE CANNOT BE REDUCED TO ZERO UNLESS THE STRUCTURE TO BE PROTECTED IS ISOLATED FROM THE LOADED MEMBER.
For confined and poorly vented compartments, leakage pressure, gas pressure and gas impulse may be estimated by assuming the net equivalent charge is reduced by 50% if the room or container interior surfaces are lined by more than 70% by BlastWrap®. Similarly, effective charge weight can be assumed to be reduced by 50% when calculating external overpressure and impulse if charges are placed in containers expected to be vent or shatter due to internal blast.
How many steps does the transmitted load estimation process involve?
There are 3 steps:
Step 1: From the scaled distance tables or formulae from which these are derived, determine pressure and impulse impinging on BlastWrap® components, and calculate peak reflected pressures and impulses using applicable references, such as TM5-1300/NAVFAC P-397/AF88-22 "Structures to Protect Against the Effects of Accidental Explosions."
Step 2: From Step 1, determine if you need Impulse Mitigator layers, and/or multiple BlastWrap®/Impulse Mitigator layers.
Step 3: To determine BlastWrap® requirements for repeated or multiple-blast environments, first estimate severity of "typical" explosion exposure. The number of layers should equal the number of moderate or stronger blasts, which must be mitigated. Weak blast environments cause little damage to BlastWrap®; thus, BlastWrap® can provide mitigation of successive explosions.
Flammable fluid and dust explosions and fireballs remove the filler-confining skin, which may spill substantial amounts of mitigating material. The same applies to severe blast exposure from detonating solid explosives. Thus if multiple exposure to fireball, flammable fluid and dust, or severe solid explosive blast is anticipated, multiple BlastWrap® layers of minimum thickness should be chosen.
Evaluating blast hazard mitigation
- Do all internal surfaces of a room or container need BlastWrap® coverage?
You should cover the maximum surface area possible without interfering with the use of the confined space. You do not need 100% coverage, however: gaps for vents, utilities, wiring, or complex geometries will have little adverse impact on BlastWrap® mitigation. Required coverage is more (at least 80%) for smaller containers than it is for large rooms or compartments. If explosives (including flammable dusts and mists) are likely to be dispersed through most of the space, then BlastWrap® coverage should exceed 90%. If the location of explosions can be predicted within a large space, BlastWrap® linings should cover at least 90% of the surface area (including roofs) within 2 meters (6 feet) of the potential explosion site (or vessel confining flammable fluids).
- Do external barriers and walls need 100% BlastWrap® coverage?
No. Covering the center portion of a barrier or wall is most important, but gaps or holes in BlastWrap® are acceptable without degrading BlastWrap® mitigation capabilities. We recommend coverage of at least 70% of the exposed surface area with BlastWrap®.
- Will fragments or other damages reduce BlastWrap® blast effect mitigation?
No. Gaps, holes, tears, and projectile penetrations involve only a small fraction of the mitigating fillers, so negligible impairment of pressure and impulse mitigation occurs in the wake of projectile damage.
How does BlastWrap® work?
It works by:
- Dissipating substantial blast energy through IRREVERSIBLE processes - drag, turbulence, friction, viscosity, etc. Very rapidly cooling blast gases.
- Slowing blast energy loading of containment to allow more venting of trapped gas - done correctly, the confining structure survives.
- For slower burning materials, (propellants, aluminized explosives and those that do not have enough oxidants) BlastWrap® interferes with secondary combustion and thus reduces heat release and gas pressurization.
The challenge is to define the blast energy released and estimate the BlastWrap® energy dissipation required. Explosive energy release definition is problematic (heat of explosion = enthalpy of combustion = heat of detonation...depending upon the author). However, BlastWrap® starts this extremely complicated process using the TM5-1300 values for "Heats of Combustion" and "Heats of Detonation." Each case is a custom-designed application, dependant upon the nature of the blast environment, blast medium and blast containment, if any.
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