Means and methods for localizing the damaging effects of an explosion.

Means and methods for localizing the damaging effect of an explosion.

Petrenko Evgeny Sergeevich

MEANS AND METHODS FOR LOCALIZING THE DAMAGING EFFECT OF AN EXPLOSION  

At present, domestic and foreign industry produces means of localizing the damaging effects of an explosion, which include anti-fragmentation blankets and mats and containers for temporary storage, carrying and transportation of explosive objects (EOD).

The domestic industry produces light and heavy anti-fragmentation blankets based on ballistic-resistant SVM fabric (a domestic analogue of Kevlar), which can be effectively used to localize the effects of an explosion of both fragmentation and high-explosive ammunition of various types.

The disadvantage of such blankets, which limits their use, is the inconvenience of laying them on the VOP, located near vertical walls, under benches, in the corners of the room, etc.

In addition, a significant drawback is the possibility of triggering fuses with an anti-removal element or a magnetic target sensor when laying a blanket on a high explosive ordnance or removing it with all the ensuing consequences for personnel, as well as the exclusion of the possibility of rendering the high explosive harmless using short-range destroyers or firearms.

It should be borne in mind that when fragmentation ammunition explodes under a blanket, for example, hand grenades of the RGO and F-1 type, there is a significant probability of some of the fragments (up to 20%) being blown out and scattered in the ground layer of air.

These same shortcomings are also fully characteristic of rubber water-filled mats, which are widespread abroad, primarily in Great Britain, and have various designations and names (photo 1).

Photo 1. Anti-bomb protective structure.

Of the containers produced by industry and certified by the State Standard, the “Pluton-1” (photo 2) and ETC-2 (photo 3) containers currently have fairly high performance characteristics.

They prevent damage to surrounding people and equipment during an explosion in their working chamber of a high explosive device with a charge weight of up to 400 g in TNT equivalent.

The design of the Pluton-1 container provides the ability to safely capture and extract fragments of explosive ordnance during its explosion in the working chamber for subsequent examination for forensic purposes.

The containers provide shielding for the receiving and executing devices of radio detonators when they are placed in the working chamber.

The weight of the Pluton-1 container is 45 kg, the outer diameter is 254 mm, the length is 480 mm, which allows it to be transported by any type of transport, including cars.

The weight of the ETC-2 container is 76 kg with slightly larger outer dimensions.

Photo 2. Container «Pluton-1» for carrying, transporting and temporary storage of explosive ordnance

Photo 3. Container ETC-2 for carrying, transporting and temporarily storing explosives

For temporary storage of items and baggage containing or capable of containing explosives, the relevant services can independently manufacture chambers of the simplest design (Fig. 1).

As the main component of the chamber design, given the absence of strict restrictions on weight and external dimensions, it is advisable to use dry fine-grained (river) sifted sand that does not contain foreign inclusions (stones).

For placing the chamber, it is advisable to use detached structures with closed rooms without windows (basement type) or structures with an easily destructible roof (wall), near which there are no electrical cables, water lines or other communications.

It is advisable to make the door to this room lattice (from rod metal or reinforcement).

The doorway of the room or easily destructible wall should be oriented in the direction of a solid wall, earth embankment, etc., where the appearance of personnel or civilians is excluded.

The working volume of the chamber should be determined by the maximum dimensions of baggage permissible for transportation by transport, as well as the possibility of simultaneous placement of several pieces of baggage.

Due to the complexity of promptly determining the location of the explosive hazard in the volume of baggage, it is advisable to ensure an equal degree of protection of the chamber in all directions.

Fig. 1. Design options for chambers for temporary storage of explosive objects

a) backfill wall;
b) chamber option with single-layer walls and a lid lined with sand-filled bags, with baggage loading from above or from the side surface;
c) a variant of a chamber with filled walls and a lid with luggage loading from the side surface;
d) a variant of a chamber with filled walls with luggage loading from above.

1 – wall made of low-density material
2 – filler (sand)
3 – bag with sand
4 – lid made of low-density material
5 – luggage with FOP
6 – sand cushion
7 – filled lid
8 – filled wall

For reliable capture of fragments of ammunition with a fragmentation shell such as hand grenades RGO, RGN, F-1, a layer of sand of at least 10 cm thick is sufficient.

Creating a chamber design that ensures the capture of damaging elements of cumulative (hand grenades of the RKG-3E type and grenades of hand-held anti-tank grenade launchers of the PG-7L, PG-9 type) and projectile-forming charges (engineering ammunition) with armor penetration from 100 to 700 mm or more, will require a layer of sand up to 1.5 m thick.

Considering the low probability of spontaneous activation of such ammunition, as well as the axial direction of their action, it is advisable to place such ammunition in the chamber so that the projectile of the striking element in the event of a possible explosion of the ammunition occurs in the direction of the wall behind which there are no vital nodes and communications.

If the room does not provide this condition, then it is advisable to make one of the walls of the chamber from a layer of sand up to 1.5 m thick.

To effectively dampen the action of the shock wave and detonation products of explosive charges weighing up to 5 kg in TNT equivalent, a sand layer of at least 25-30 cm thick can be used.

The shock wave energy is almost completely spent on adiabatic compression of air inclusions and throwing fine sand, and the detonation products are intensively cooled.

During the detonation of 1 kg of TNT explosives, up to 1000 liters of gases (at normal pressure) and up to 1100 kcal of thermal energy are released.

With an average sand density of 1.6 g/cm3, the specific gravity of 1 m2 of the protective structure will be 400-480 kg.

The following variants of the chamber design may be proposed: a backfill variant and a variant with single-layer walls lined with polyethylene or paper bags (sacks) filled with sand.

The chamber walls must be made of non-metallic materials such as textolite, multilayer plywood, chipboard, etc.

It is possible to implement two variants of baggage loading in the chamber design: with loading through the top (removable lid) and with loading from the side wall (movable wall).

In all cases, a sand cushion of at least 25-30 cm thick must be placed under the working volume of the chamber. The thickness of the sand layer on the chamber cover must be at least 15-20 cm.

In all cases, it is necessary to ensure sufficient rigidity of the structure, eliminating the possibility of spontaneous destruction of the chamber under conditions of static loads from the filler.

To prevent the formation of high-energy secondary fragments during an explosion of baggage in the working volume of the chamber, the connection of the structural elements must be carried out using low-density materials: plastic, wood, aluminum-based alloys, nylon, etc.

When assembling the chamber, mutual overlap of the joined faces must be ensured.

To prevent the possibility of remote triggering of radio fuses, the chamber walls from the inside or outside over the entire working volume must be lined with metal (metallized) foil or metal mesh with a cell size of no more than 1 cm. The foil or mesh must be grounded by connecting to the building grounding circuit.

To localize the damaging effect of a VOP explosion during its self-destruction, polyethylene or paper bags with sand or other loose filler (soft soil, fine slag) can be used (photo 4).

The thickness of the filler layer in the direction of the protected sectors of space must be at least 15 cm for charges weighing up to 200 g in TNT equivalent.

This design allows for the rapid erection of a protective wall and at the same time does not interfere with subsequent actions to neutralize the explosive hazard.

Photo 4. Paper sandbags as a circular means of localizing the effects of an explosion.

Portable hollow plastic barriers, which have recently appeared among city road services, can be used as an effective means of shielding the sectors of fragmentation and shock wave propagation. They are installed temporarily on roads during repair work or to separate oncoming traffic flows in narrow sections and are filled with water after installation (photo 5).

Photo 5. Plastic waterproof barriers

Such barriers, having a length and height of about 1 m, and a thickness of about 25-30 cm, provide braking of fragments of most ammunition and significantly weaken the shock wave due to the processes of reflection of the shock wave from a denser medium, which is water in relation to air, and the energy costs of throwing water.

Flexible hoses like fire hoses (Fig. 2) or fragments of polyethylene hoses 1.0…1.5 m wide, used by gardeners to set up greenhouses, can be used as a makeshift means for creating a circular or sectorial protective screen based on sand or water.

For ease of bending the hose when laying it near a fire hazard, the internal volume of the hose is not completely filled with sand or water, but with air pockets.

For the same purpose, it is advisable to use primarily previously used fire hoses, including those written off due to the impossibility of using them for their intended purpose.

The latter, in addition, should be divided into sections from one to several meters long.

Fig. 2. Option for laying a water-filled fire hose around a VOP.

The hose is laid around the VOP without contact with it (the distance from the hose to the nearest VOP surface can be from a few centimeters to 1-1.5 m). In some cases, for example, when the VOP is located near a vertical wall, the hose can be laid as a vertical screen to protect a certain sector of space.

For the convenience of creating a volumetric screen based on a fire hose, a framed collapsible structure made of rods, mainly made of light non-magnetic aluminum-based alloys, can be used, similar to those used in the widely used quickly erected collapsible trade tents and garden greenhouses (Fig. 3).

In addition, when using such a design, it becomes possible to place a certain number of turns of the hose above the explosive device, thereby ensuring the possibility of complete shielding of the upper half-space.

In the event of an explosion of the explosive device, light rods with a low transverse load value (the ratio of the mass of the resulting fragments to the area of ​​their cross-section) are thrown by the explosion over an insignificant distance.

It is advisable to fill the hose with sand in advance.

Filling the hose with water is carried out, depending on the specific situation, either before it is installed near the VOP, or after installation.

To eliminate the danger of throwing massive connecting couplings of the fire hose in the event of a possible explosion, these couplings must be removed from the VOP by at least 1-1.5 m or cut off (in this case, the ends of the hose in a water-filled state are tied together).

Fig. 3. Option for laying a water-filled fire hose around a fire extinguishing facility using quickly erected, collapsible trade tents and garden greenhouses

With a hose diameter of 0.1 m (fire hose) and its laying in two turns (in the horizontal plane) or more, effective circular or sectoral protection of the surrounding space from the damaging factors of an explosion (shock wave and fragments) of various explosive charges and ammunition is ensured.

In addition, laying the hose in two turns or more, when adjacent turns are not rigidly connected to each other, eliminates the possibility of their simultaneous “jumping” during an explosion of an explosive charge and blowing out some of the flying fragments, which is typical for structures such as anti-fragmentation blankets and mats.

Effective protection against the high explosive action of shell-less high explosives with a charge weight of 0.75-1.0 kg, which is especially important in urban conditions with significant glass areas and a high probability of people being injured by glass fragments, can be ensured by using liquid or condensed porous materials with a density of 0.01-1 g/cm3.

For these purposes the following may be recommended: foam barriers created by foam fire extinguishers; polyurethane foam; packaging foam plastics and fast-hardening polyurethane foam compositions such as “Macroflex”, “Penoflex”, used in construction for heat and sound insulation of premises (the volume of foam created using one canister is 30-50 l).

The use of porous materials together with structures made of materials with a density of 2.1 — 7.8 g/cm3 (fiberglass, sheet steel) allows for protection against fragmentation ammunition. With a total thickness of the protective barrier equivalent to 6 mm of sheet steel, the localization of the scattering of damaging elements of hand fragmentation grenades and artillery ammunition with a caliber of up to 120 mm is ensured.

The domestic industry has developed protective structures in the form of an urn, intended for placement in government and state institutions, railway stations, airports, places of mass gatherings of people, etc. (photo 7).

This design ensures the localization of the damaging effect of fragmentation and shell-less explosive devices with a charge weight of 0.075 — 1.0 kg in TNT equivalent, which seems relevant in the context of the possible use of garbage bins to place explosive devices for terrorist purposes.

Existing bin designs are usually made of metal, which leads to an increase in the damaging effect of the explosion of shell-less explosive devices due to the fragmentation of the bin body.

The developed urn does not form fragments when a shell-less explosive detonates in it and reduces the high-explosive effect to a safe level, and when fragmentation ammunition explodes, it ensures reliable capture of the resulting fragments along with a reduction in the high-explosive effect.

In addition, such an urn can be used to neutralize detected and identified explosive detonators: this object can be covered with an urn; the urn can be used to shield the most critical sectors of the action of damaging factors of the explosion, and can also be used together with a halyard to unseat suspicious objects.

Photo 7. Explosion-proof urn

Effective all-round protection against damaging factors of explosion of shell-less explosive devices with a charge weight of up to 400 g in TNT equivalent and fragmentation ammunition such as hand grenades can be provided by using car tires installed on top of each other in a column (photo 8).

To limit the impact of a more powerful explosive charge, a column of tires should be reinforced all around or in the most critical sectors with sand-filled polyethylene or paper bags.

Photo 8. Explosion-proof structure made of car tires

In winter conditions, effective protection against the high-explosive effect of an explosion of explosive charges weighing 0.2-0.4 kg can be provided by using snow screens 0.5-1 m thick.

It should be noted that the most universal and generally accessible method of protection against the damaging effects of explosions of both uncased explosive charges and fragmentation ammunition is protection by distance (Table 1).

Table 1. Possible range of fragments during an explosion of ammunition

At the same time, fragmentation ammunition is characterized by both a decrease in the speed of individual fragments due to braking by the air environment, and a decrease in the density of diverging fragmentation flows.

In general, the localization of the damaging effect of the explosion of explosive remnants of various types is a very urgent task, for the solution of which both industrially produced means and improvised means and materials can be used with varying degrees of efficiency.

Naturally, all actions to use the means and methods discussed in this article must be carried out by authorized officials who have undergone special training, in strict accordance with job descriptions.