AU661558B2 - Explosives segregation method - Google Patents

Description

P/00/011 Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "EXPLOSIVES SEGREGATION METHOD" The following statement is a full description of this invention, including the best method of performing it knlown to me:- AUS 1505 2 EXPLOSIVES SEGREGATION METHOD The present invention relates to a method for the segregation of detonators from high explosives, enabling safe storage and transportation of such goods. The present invention further provides a blast barrier suitable for the segregation of detonators from high explosive in accordance with Clause 7.3.3 of the Australian Explosives Code.

S• 10 The transport of explosives on public roads is regulated in each state of Australia by the responsible State Authority. Whilst in general small quantities of explosives and detonators may be carried in locked carrying boxes and transported in separate parts of the same vehicle, large quantities of high explosives and detonators may only be transported to a blast site in separate vehicles.

The main purpose of segregated transportation is to keep the two.types of explosives sufficiently separated to prevent communication of an explosion from the detonator to the other explosives in the event of accident.

-3- It is clearly apparent that the cost and inconvenience of tranporting detonators and explosives separately could be greatly reduced if a safe method of transporting both goods together could be implemented. While it is currently not lawful to carry detonators on any vehicle containing 1000kg or more of explosive of another hazard division or compatibility group, such transportaion is acceptable where a separation or protective mechanism has been demonstrated to effectively prevent the communication of fire or explosion from detonators to the other explosives. (Agenda Item 7(1) Commonwealth Inspectors of Explosives conference, 11th to 14th October 1988).

It is difficult to develop a suitable method for transport of detonators and high explosives together on the same vehicle due to the large number of variables involved. It requires a consideration of how to minimise factors which may propagate an explosion from detonators to other explosives such as blast impact force, flying detonators and shrapnel.

Propagation of an explosion from exploding detonators to other explosives during transport can be influenced by many and diverse factors including distance between detonators and other explosives, geometry and materials of construction of the containers and other elements, the presence of any barriers between the loads, the packing density of the detonators, the mass of each explosive load and the time delay spread of the detonators.

Practical field testing is somewhat hampered by the difficulty of '"scale-up". A barrier which is S. successful with small quantities of detonators and high explosives will obviously not necessarily be successful at preventing propagation of detonation between much larger quantities hence there is always -4a requirement of full scale testing. This may be both expensive and hazardous.

It has now been found that the problem of safely transporting on storing detonators and explosives together can be overcome by utilising a new method of transportation and storage a comprising a blast barrier. There is therefore provided, according to the present invention, a method of segregating detonators and high explosives of another hazard division or compatibility group on the same vehicle or during storage comprising locating a blast barrier between the detonators and high explosives, enclosing the high explosive load in a container which can withstand the impulse loading from the barrier without rupture and providing an air gap between the detonator load and the blast barrier.

In a further embodiment the invention provides a blast barrier comprising a plate covered with blast absorbing material said blast barrier being located between a detonator load and a high explosive load but not in physical contact with said detonator load.

The current invention was developed by iomputer 25 modelling combined with selective full-scale field testing of certain models to confirm the accuracy and efficacy of the computer modelling. The modelling of various explosives segregation methods was carried out using DYNA3D, a program developed at Lawrence Livermore National Laboratories, USA by John Halpquist. This program is well known in the art as S. a code commonly used for motor vehicle crash worthiness testing.

These techniques have developed a method of segregation having three critical components, specifically, 5 the placement of a blast barrier between the detonator and high explosive loads to protect the high explosive from a mass detonation of detonators, enclosure of the high explosive load in a container which can withstand the impulse loading from the barrier without rupture and the provision of a gap between the detonator load and the blast barrier, Avoiding direct physical contact between the barrier and the detonator load protects the barrier from direct detonation effects.

The method of segregation has several components which are subject to existing regulation but are non-critical to the performance of the segregation method and these include; the design of an explosive compartment which is capable of withstanding the impulse loading from the barrier without rupture, the design of the detonator carry box such that it protects the barrier from the direct detonation effects and is of such dimensions that it can be contained within the detonator compartment,

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the use of materials of construction for the explosives compartment, the detonator compartment and the explosives carry box which do not detract S. from the strength of these elements, the method of fixing the compartments to the transport vehicle, and the method of weather proofing the blast barrier.

6- Where used herein the term "detonator load" means detonators or pentaerythritol tetranitrate (PETN) based primer compositions such as "ANZOMEX", (Registered Trade Mark of ICI Australia Operations Proprietary Limited).

Where used herein the term "high explosive" means any explosives other than detonators, that is, explosives of another hazard division or compatability group. This would include explosives such as nitro-glycerine based explosives, sensitized emulsion explosives, detonating cord, PETN based primer compositions and cast pentolite primers.

Where used herein the term "explosives compartment" means a container in which one or more high explosive is located for transportation. In a preferred embodiment the explosive compartment is a shipping container, lined with wooden panelling or other suitable material.

Where used herein the term "impulse loading" means the force exerted due to the detonation of a detonator load.

Where used herein the term "blast barrier" means a fixture placed between the detonator load and the high explosive load. It is preferable that the blast barrier should be a permanent fixture to the high explosive container, located at or near one end of the explosive compartment and the explosive compartment is constructed or reinforced so as to be capable of withstanding the impulse loading from the blast barrier without rupture.

In a particularly preferred embodiment the blast barrier comprises a plate made of a convenient material such as metal, attached to the outside end wall of the explosive compartment and covered with blast absorbing material such as wood. Materials such as vermiculite and polyurethane foam have also 7 been found useful but wood is the preferred material. Other suitable materials will be evident to those skilled in the art.

The plate of the blast barrier may comprise a single piece of metal or other suitable material or it may be constructed of smaller relatively flat pieces of metal joined together. In a preferred embodiment, small relatively flat pieces of metal are welded together using a continuous weld and may contain cut-out sections for access to the lifting points on the container. The plate may also contain cut-outs to access the container anchor points.

Where used herein the term "detonator compartment" means the container in which detonators are transported. The detonator compartment may have provision for a removable "detonator carry box" for housing the detonators. Optionally the detonator carry box may be locked into position within the detonator compartment such that it will not move during transport, particularly if the vehicle and detonator compartment should move violently in the event of the vehicle being involved in an accident.

The dimensions and materials of construction of the detonator compartment and detonator carry box are 25 non-critical but preferably at least meet the requirements of section 6.2 of the Autralian Explosives Code. A critical feature of design of the detonator compartment is a gap between the detonator carry box and the front of the blast barrier. Preferably the gap is an air-gap at least 500 mm wide. In a preferred embodiment a gap is provided between the detonator carry box and all walls of the detonator compartment. It is preferred that constructions lying within the gap, that is, between the detonator carry box and the walls of the detonator compartment are constructed of lighter 8 weight materials than the compartment walls. In a preferred embodiment such constructions are made of wood or 2 mm steel forms or sections.

In a particularly preferred embodiment, two gaps are provided, one between the detonator carry box and the front of the blast barrier and the other between the end wall of the explosive compartment and the wooden lining of said compartment. The latter can conveniently be provided by the use of pieces of channel iron to reinforce the end wall of the explosive compartment, one side of the channel iron being attached to the end wall and the other side being attached to the compartment lining.

Preferred embodiments of the present invention will now be described by way of the following examples and with reference to the accompanying drawings in which; Figure I is a plan view of an explosives S* compartment; Figure 2 is a view of the rear wall of 20 the explosive compartment; Figure 3 is a rcross-sectional view along A-A' of Figure 2 and 'shows an expanded view of the inside back wall of the explosive compartment; Figure 4 is a view of the S9. detonator carry box; and Figure 5 shows a preferred arrangement of the e:plosives compartment and detonator carry box.

#The preferred embodiments of the present invention are further described and demonstrated by the following'examples and accompanying drawings in which; a.* Figures 6(c) and 6(d) are a series of computer simulated cut-away drawings of the explosive compartment and blast barrier of Example 1 subjected to detonators exploding; and Figure 7 shows an unreinforced explosive compartment.

The invention depicted in Figure 1 includes a rear wall of an explosive compartment which is reinforced by pieces of channel iron attached to thG inner side of the wall and vertical corner supports. Further reinforcing is provided by a steel plate which is continuously welded with plug welds to floor beams of the explosive compartment.

15 The channel iron is bolted on its other side to the explosive compartment lining consisting of wooden battens to which a plywood wall is nailed. In a preferred embodiment the blast barrier is located on the outside rear wall of the explosive compartment and comprises a steel plate continuously welded to the edge of the explosives compartment to which is attached a layer of vertical planks of wood and a layer of horizontal planks nailed together at each crossing. Figure 2 shows the arrangement of the steel channels and wooden battens Figure 4 is a view of the preferred embodiment of the compartment in which the detonators are stored and the air-gap (9) between the detonator compartment and the front of the blast barrier 10 The following example describes a barrier and high explosives compartment design which has been demonstrated to meet the critical requirements. The person skilled in the art will be able to see many further embodiments of the invention which are within its scope. The attributes and preferred embodiment of the invention is further revealed by the following non-limiting example.

A standard ISO 6.1m shipping container was modified in accordance with section 6.3(n) of the Australian Explosives Code for the transport of explosives to function as an explosives compartment.

In addition a blast barrier was fixed to the outside rear wall and the container was reinforced.

The blast barrier consisted of: a 3 mm 250 grade steel plate continuously welded to S. the strength members at the four edges of the end of the container.

o* two criss-crossed layers of dressed Australian hardwood of grade F8 or better with each layer having a final dressed thickness of at least 68 mm; the layers of wood being held together by one nail at each crossing, and said barrier was permanently affixed to the container using at least six M12 bolts or stronger.

The strengthening of the container to support the barrier consisted of: 11 a 6mm 250 grade steel plate to the bottom of the container from the middle of the bottom strength member back at least 900mm and continuously welded at the edges and with plug welds to the floor support beams and five 75 x 40 mm 250 grade steel channels stitch wel2ed horizontally across the inside of the end wall, to the strength members on either side of the wall and at several points to the corrugated end wall.

The steel channels were bolted to the wooden battens of the container lining.

The current invention is further demonstrated by Figures 6(c) and This is a 15 series of computer simulated cut-away drawings of an ;explosive compa'rtment and blast barrier as described in Example 1 as it is subjected to the force of 000 standard detonators exploding in a 'detonator compartment. The explosive compartment, 20 blast barrier and detonator compartment were arranged as shown in Figure S• Figure 6 clearly shows the explosives compartment (container) wall reinforcing members and wooden battens and plyboard lining the explosives compartment.

Figure 6(a) shows the explosives compartment at t=0 seconds from detonation, Figure 6(b) is at ms from detonation, Figure 6(c) is a t-10 ms from detonation and Figure 6(d) is at t=15 ms from 12 detonation. Figures 6(c) and 6(d) are nearly identical, indicating that most of the deformation of the explosives compartment had occurred by about Figure 7 shows a computer simulation of an explosives compartment at t=3 ms after it has been subjected to the force of 10 000 standard primer detonators exploding in a detonator compartment in the same circumstances as Example 2.

The difference however in this simulation is that no reinforcement has been used to strengthen the shipping container.

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Claims (9)

1. A method for segregating civilian detonators and high explosives of a different hazard division or compatibility group on the same vehicle or during storage comprising locating a blast barrier between the detonators and said explosives, enclosing the detonators and explosives of a different hazard division or compatibility group in an explosives compartment which can withstand an impulse loading from the blast barrier without rupture and providing an air-gap between the detonators and the blast barrier.

2. A method for segregating civilian detonators and high explosives of a different hazard division or compatibility group according to claim 1 wherein said detonators are housed in a detonator carry box which is removably located within said explosives compartment.

3. A blast barrier for segregating civilian detonators and high explosives of another hazard division or compatibility group comprising a plate covered with blast absorbing material, said blast barrier being located between a detonator load and explosives of a different hazard division or compatibility group but not in physical contact with said detonator load, the detonators, explosives and blast barrier being enclosed within an explosives compartment which can withstand an impulse loading from the blast barrier without rupture.

4. A blast barrier for segregating civilian detonators and high explosives of another hazard division or compatibility group according to claim 4 wherein said barrier is separated from the detonator by a gap.

5. A blast barrier according to Claim 3 wherein said plate is attached to the outside end wall of an explosive compartment and said explosive compartment is constructed or reinforced so as to be capable of withstanding the impulse loading from the blast barrier without rupture. -14-

6. A blast barrier according to claim 3 or 5 wherein said plate comprises one or more relatively flat pieces of metal.

7. wide. A blast barrier according to claim 3 wherein said gap is at least 500mm

8. A method of segregating detonators and explosives of a different division or compatibility group substantially as hereinbefore described with reference to the embodiments as shown in the accompanying drawings 1 to

9. A blast barrier substantially as hereinbefore described with reference to the example. A blast barrier substantially as hereinbefore described with reference to the embodiments shown in the accompanying drawings 1 to Dated 9 March 1995 ABSTRACT The current invention relates to a method for segregating detonators and explosives of a different hazard division or compatibility group on the same vehicle or during storage comprising locating a blast barrier between the detonators and said explosives, enclosing the explosive load in a container which can withstand the impulse loading 'from the barrier without rupture and providing an air-gap between the detonators and the blast barrier. C e e **eee