GB1605450A - Protective systems - Google Patents

Description

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PATENT SPECIFICATION

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(21) Application No. 16828/77 (23) Complete Specification filed 06/01/1978 (44) Complete Specification published: 25 April 2007

(51) International Classification7 F42B 39/20

(52) Index at acceptance A5A, A28: F3A, AB3

(22) Filed 31/01/77

(72) Inventor(s)

BERNARD MICHAEL MURPHY, JOHN HENRY SINDLL,

PETER BRIAN STOKES

(54) PROTECTIVE SYSTEMS

(71) We IMI KYNOCH LIMITED, formerly known as Imperial Metal Industries (Kynoch) Limited, a British Company, of Kynoch Works, Witton, Birmingham B6 7BA and Bernard Michael Murphy of "Three Gables", Irton, Holmrook, Cumbria, formerly of 18 Berkeley Court, Oatlands Drive, Weybridge, Surrey, a british subject do hereby declare the invention, for which we pray that a patent may be granted to us, and 5 the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to storage apparatus for storing combustible materials particularly but not exclusively gun propellants.

10 Gun propellants are combustible materials, the burning rate of which increases with increasing pressure. Storage of propellant on fighting vehicles, for example tanks and ships, is a long standing problem. The storage apparatus is clearly liable to "attack" whether directly by an aimed projectile or incidentally due to a splinter or fragment from a near-by explosion. If stored propellant is ignited, the effect of a propellant explosion may be far worse than the effects of the initial attack.

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Increased armouring of propellant stores is only a partial answer. Firstly, it carries a weight penalty, so that the manoeuvrability of a fighting vehicle may be reduced. Secondly, no armour can be made fool proof, and all metal armour tends to heat fragments which do penetrate it - thereby increasing the risk of ignition of combustible material stored within it.

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There have been at least two prior attempts to deal with this problem as disclosed in UK Patent Specifications 1 121 521 and 1 213 138. These prior attempts are intended to prevent ignition of the propellant even if a fragment succeeds in penetrating the surrounding protection. The present invention is based upon an entirely different approach, which accepts the possibility that the stored material will be ignited during an attack. 25 It is to be noted, however, that both the invention and the prior art are designed only to deal with localised attacks on a storage apparatus with a projectile or fragment substantially smaller than the apparatus. The invention is not designed to deal with catastrophic situations.

According to the present invention there is provided a storage apparatus for storing combustible material, 30 the apparatus comprising a plurality of mutually isolated, closed compartments for containing said material, each compartment having a removable closure to enable access to be had to the interior of each compartment and additionally having compartment venting means for venting combustion gases, produced in the event of combustion of said material in one or more compartments, from said one or more compartments to a zone remote from each closure, the venting means being arranged to vent the combustion gases when the pressure 35 thereof in a compartment exceeds a predetermined minimum value. The venting means may be adapted to prevent the pressure around any compartment contents reaching a level which will support explosive combustion.

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The compartments may comprise a plurality of containers mounted, in predetermined spaced relationship, in a housing.

The zone to which combustion gases are vented should be a pressure and/or temperature sink. Preferably 5 the gases are vented to atmosphere, but they may be vented to a suitable reservoir if operating conditions permit this.

Some or all of the compartments may be individually vented, for example by means of respective openings through a housing wall. Alternatively there may be a common vent for some or all of the compartments. 10 Where a space is provided between compartments, this space may be separately vented.

The housing may comprise a tough, rigid wall which is preferably designed to resist penetration. It may be made of a composite material or a single material. Materials which can be used for the housing include metals, very hard materials such as ceramic, and plastics materials including fibre reinforced plastics materials. A 15 non-metallic material is preferred to avoid heating of any fragment which penetrates the housing wall. This wall may or may not be self-sealing dependent upon the required conditions of use.

Each compartment is preferably such as to protect the contents of an individual compartment from the combustion products of material in another compartment. Further, each compartment preferably has at least a 20 degree of self-sealing on penetration by a localized attack. Further, each compartment is preferably such that it retains its integrity under internal pressure even after penetration by a localized attack. Each compartment preferably comprises a rigid, tough surrounding wall to reduce the chances of penetration thereof, although the wall of each compartment may be not as tough as the wall of a surrounding housing.

25 The venting means for each said compartment preferably comprises blow out means which will open up a flow passage for gases from the compartment in response to a substantially predetermined internal pressure. The blow out means is however preferably resistant to external pressure and impact. The blow out means may comprise a closure which is preferentially breakable or separable from the compartment. The access closure for said container, or any other form of compartment, preferably comprises a closure which is resistant 30 to substantially higher internal pressures than the venting system.

A layer of elastomeric material in the compartment wall can provide both a degree of self-sealing and thermal insulation. Toughness can be provided by glass fibre reinforced plastics. The reinforcing fibres may be filament wound into the compartment wall. Suitable elastomers are those used in combustion inhibitors and 35 insulating linings in rocket motors for example chloro-sulphonated polyethylene and ethylene-propylene terpolymers.

Each compartment may be arranged to receive a predetermined quantity of solid combustible material. The quantity in any one compartment may be designed for use as a unit. In the drawings each compartment is 40 designed to contain a body of gun propellant suitable for normal operation of a given gun, but a compartment can be designed to receive several such bodies or only part of such a body. The compartments may be designed to receive quantities of the same size or of the same type of combustible material.

By way of example embodiments of the invention will be described with reference to the accompanying 45 diagrammatic drawings wherein

Figure 1 is a sectioned perspective view of a first embodiment Figure 2 is a section elevation of a second embodiment,

Figure 3 is a section through a part of a vented container,

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Figure 4 is a diagram for use in explanation of Figure 3.

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Each of the embodiments is designed to store gun propellant on a fighting vehicle such as a tank or a ship. In the first embodiment, the storage apparatus as a whole is designed to be located within a "sensitive" compartment of the vehicle. This will usually be a crew compartment, but it might also be a compartment designed to contain sensitive equipment without necessarily containing personnel in normal use. As illustrated in Figure 1, this embodiment is designed for use where there is no direct access from the compartment to the atmosphere, which is to serve as a temperature and pressure sink for combustion products of propellant stored in the apparatus.

The illustrated apparatus comprises a housing having a laminated wall 20 which includes one or more layers of a tough, non-metallic material such as glass fibre reinforced plastics. The wall structure also comprises one or more layers of an elastomeric material of the type used in combustion inhibition of rocket motors. The elastomeric material is preferably based on chloro-sulphonated polyethylene, with or without suitable additions such as fillers to provide the desired properties for the present application. Although only two layers are indicated on the diagrammatic drawing, it will be understood that a wall comprising more than two layers may be built up as thought fit depending upon the circumstances.

At one end, the tubular wall 20 had an end plate 22 secured thereto and at the other end a plate 24. Each plate has a projecting flange 26, 28 respectively into which the tubular wall 20 is fitted and to which it is adhesively secured.

Plate 22 has an opening 30 for a purpose to be described in greater detail below. Plate 24 has four openings, one of which is indicated at 32 in Figure 1, the others being equi-angularly spaced about the longitudinal axis of the wall 20. Each opening 32 receives in use a container 34, two of which are seen in Figure 1. Each container wall is a laminated structure comprising at least one inner layer 35 of an elastomeric material and at least one outer layer 36 of wound glass fibre filaments. The elastomeric material is again based on an elastomer of the type used in combustion inhibition of rocket motors, for example chloro-sulphonated polyethylene. At its lower end each wall 35, 36 is adhesively secured in a metal rim structure 40, and at its upper end the wall is secured in a metal rim structure 42. Secured to the rim structure 40 by means of a plurality of bolts 39 is a disc 38 which normally closes the lower end of the container. The rim structure 42 comprises an inwardly projecting flange 44, which abuts the upper end of the laminated wall 35, 36, an upstanding tubular wall 45 which is internally screwthreaded, and a radially outwardly extending flange 50 having a plurality of angularly spaced bolt openings 51 therein. In use, the container 34 can be closed by a disc-like closure element 46 having external screwthreads designed to co-operate with the threads on the tubular portion 45, and having a suitable grip 48 to enable the closure to be easily connected to and removed from its container.

In use of the illustrated apparatus, it is located within, say, a crew compartment of a fighting vehicle, for example within a tank or within an enclosure around a ship gun. The opening 30 in the plate 22 is connected to a duct (not shown) which leads to a suitable location on the exterior of the vehicle. Individual charges of gun propellant are located in individual containers 34, which in turn are mounted in the end plate 24 by means of bolts 52 extending into aligned screwthreaded openings in the end plate 24. Each charge of propellant is designed to rest upon flange 44, and has a gripping means which is presented at the entrance to the container when the closure disc 46 has been removed therefrom. The screwthreads on the wall 45 are of the multi-start type, so that the closure disc 46 can be secured to and released from its wall 45 by a quarter turn. Thus, propellant in each container 34 is ready accessible to the gun crew.

In action, the wall 20 and wall 35, 36, may be penetrated by a "fragment", for example a slug produced by impact of a hollow charge projectile with metallic armour defining the compartment. The hot fragment will probably ignite the propellant in a container 34 which is penetrates. The elastomeric material in the wall 35,36 and in the wall 20 tends to seal the entrance holes behind the fragment, so that when the propellant is ignited pressure begins to build up within the container 34. The glassfibre filaments in the layer 36 withstand this pressure, which is therefore imposed upon the disc 38 and its securing bolts 39. These are designed to rapture at a predetermined pressure within the container 34 to release that pressure and the combustion

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gases towards the opening 30, through which they can be ducted to the exterior of the vehicle as described above. The arrangement for securing the closure disc in place in its rim structure 42 is relatively strong, so that the disc 38 will blow out leaving the closure disc 46 securely in place to protect the interior of the crew compartment. Further, the self-sealing characteristics of the wall 20 will prevent penetration of the combustion gases to the interior of the crew compartment. O-ring seals 53 are provided in the rim structures 42 to contact the plate 24 and prevent leakage of gases from the storage apparatus.

A filament wound structure of glass fibre filaments or rovings will retain its integrity even if penetrated locally. It is assisted in this by the internal layer 35 of elastomeric material which acts as a thermal insulator to protect the glass fibre layer 36 from the full thermal effects of the ignited propellant within it. Thus, the container 34 with the ignited propellant directs the combustion gases towards the end plate 22 and the vent opening 30 therein. Preferably, the innermost layer of the wall 20 is also of elastomeric material to protect glass fibre layers in that wall from the thermal effects of combustion ases remaining in the storage apparatus. The elastomeric material in containers 34 containing non-ignited propellant will protect the contents of those containers from the combustion gases of the ignited propellant, thus preventing "cook-off' of the contents of non-penetrated containers.

It is not essential to vent combustion gases of several containers via a common opening 30 and a single duct as described above. Clearly there could be a plurality of ducts associated with respective containers, so that each container is vented separately. It would still be preferable to provide a further vent for the space within the storage apparatus between the containers 34. This will be the preferred arrangement where the compartment in which the storage apparatus is located has direct access to an external wall. The end plate 22 of the apparatus can then be incorporated in the external wall, and the containers can be individually vented via respective openings in the end plate 22, the plate 22 comprising an additional opening for combustion gases within the apparatus itself. Clearly, however, if the individual containers can be made fully self sealing, the additional vent for the storage apparatus may be unnecessary, and self-sealing properties for the wall 20 would then also be unnecessary. If the individual discs 38 are to be accessible to the exterior of the vehicle, then preferably each is individually armoured to make it substantially more resistant to external pressure and impact than it is resistant to internal pressure and impact. The illustrated arrangement permits this, because each disc 38 is retained against movement towards the interior of its container by full face engagement with the rim structure 40, whereas it is held against movement away from the interior of its container only by the bolts 39.

Figure 2 illustrates a modified embodiment which is designed as an external appendage to a fighting vehicle such as a ship or a tank. If this embodiment were used in a ship, it could be mounted upon deck space adjacent a gun. If it were used on a tank, it could be arranged to be connected to a suitable portion of the tank so as to project from the body thereof. The Figure 2 embodiment comprises an armoured housing made up of a tubular shell 60 with a pair of armoured bulk heads 62,64 respectively. The armour of the housing could be of a conventional type comprising a suitable steel or other metal alloy. It could also be a composite armour of one of the many now well known types. Provided the access bulk head 62 is in a protected position, for example incorporated in the wall structure of a tank or gun compartment, the housing of the Figure 2 embodiment may not be self-sealing.

Each bulk head 62, 64 has an array of openings 66, 68, the arrays being aligned with each other so that a plurality of containers 70 can be suspended between the bulk heads 62 and 64. Suitable means (not shown in Figure 2) can be incorporated in each container and/or in the bulk heads 62,64 to prevent axial movement of the container 70 relative to their respective openings 66, 68.

Each container 70 may be similar to the container 34 in comprising a tough outer layer and a liner of material resistant to combustion gases of propellant. At the end mounted in the bulk head 64, each container is closed by a blow out disc 72, and at the end mounted in the bulk head 62 the container is closed by a quick-release closure disc 74. Suitable sealing means (not shown) is incorporated in each container to seal with the bulk head 62 within and/or around the opening 66 to prevent combustion gases within the housing leaking through

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the joint between the container 70 and the bulk head 62. The bulk head 64 has a plurality of additional openings 76 for venting combustion gases in the housing in a known and controllable manner.

If it is not desired to present the ends of the container 70 to the exterior of the vehicle as illustrated in full 5 lines in Figure 2, the shell 60 may be extended as shown in dotted lines 78. In this case suitable vent means must be incorporated in the extension 78. For example, the extension could include armoured louvers which will open in response to internal pressure but which will tend to close under external pressure and/or impact. Alternatively, the extension 78 could include an open-work structure such as a frame-work filled in with a mesh-work through which combustion gases can escape. In the event that the extension 78 provides 10 sufficient armour protection, it may not be necessary to armour the bulk head 64, which could then be formed as a simple support member of framework for the containers 70.

The housing may have means (now shown) for enabling it to be attached as a unit, with a filled load of containers 70 and propellant charges, to a fighting vehicle. This will enable very rapid loading and unloading 15 of propellant charges to a fighting vehicle at a base depot in use.

Figure 3 illustrates in section the ends only of a container suitable for use as the container 70 or in substitution for the container 34. The container of Figure 3 comprises an outer cylindrical layer 80 of resin impregnated, wound, glass fibre filaments. Within this is a layer 82 of chloro-sulphonated polyethylene (for example that 20 sold under the trade mark "Hypalon"). Within the layer 82 is a thin layer 84 of resin impregnated wound glass fibre filaments. The dimensions of the various layers may depend upon the required circumstances of use, but it has been found suitable to use a layer of elastomeric material having about 1/4 to 1/6 the wall thickness of the layer 80.

25 At one end the wall structure is adhesively secured to a metal rim 86 which includes an outwardly projecting flange 88 having screwthreaded openings 90 to receive bolts for securing the rim to a support structure such as the bulk head 62 or the end plate 24. Preferably the surface 91 of the flange 86 engages the bulk head or end plate in use, so that the latter provides a support to bear axial forces on the rim structure caused by internally screwthreaded tubular projection 92 to receive a closure disc 94 similar to the disc 46 described above. Disc 30 94 may be of a suitable metal with a layer of insulation 93 located inside the container when the closure is in place. An O-ring seal 95 is located in a suitable channel in the projection 92 so as to engage with the disc 94. A stiffening sleeve 96 may be provided on the interior of the wall of the container within the rim 86 to reduce the risk of leakage of external gas into the container due to breaking of the bond with rim.

35 At its other end, the wall structure has an internal rebate to provide a shoulder 97 which receives a correspondingly formed blow out disc 98. Disc 98 and the wall structure are normally secured against relative axial movement by a plurality, say four, of shear pins 100 extending through aligned holes in the wall and the discs. The pins 100 are designed to fracture at a predetermined pressure within the container to permit blow out of the disc 98 and release of combustion gases within the container. Connected to the 40 disc 98 by a compression spring 102 is a disc 104 of insulating material which engages one end of a unitary propellant charge inserted into the container in use, thereby providing a resilient support for the propellant charge within the container. The disc 104 is slightly spaced from the internal surface of the container to permit combustion products in the upper part of the container to reach and act on the closure disc 98. An O-ring seal 99 is however provided between the disc and the internal surface of the container so that the latter 45 is normally substantially airtight. Thus, the charge can be so designed in relation to its container that the air within the container will provide cushioning of movement of the charge into the container, avoiding undue impact forces upon the disc 98 in use. The substantially airtight construction also protects the charge from environmental effects, for example dust and humidity, during storage. The surface of the disc 98 within the container may be insulated, but this will not be essential if the end of the charge is separated from the closure 50 disc, for example by a compression spring as shown in the drawing. The disc 98 may itself be armoured, or it may be of a light construction to which an armour shield can be secured in use if required. Since the disc 98 is located within the lower end of the container, there is no need for an internal support sleeve similar to the sleeve 96 at the upper end.

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Figure 4 is a diagram illustrating a burning time (BT) to pressure (P) relationship for a propellant of the type which might be stored in an apparatus in accordance with the invention. It will be seen that the pressure at first rises relatively slowly with time, but reaches a stage at which burning becomes exponential and potentially explosive with a relatively rapid increase of burning rate with increase of pressure. The venting system of 5 the storage apparatus must be designed to release pressure around the combustible contents before it can reach this second, explosive stage of combustion, for example by causing the pressure to follow the dotted line path shown in Figure 4. It will usually be desirable, therefore, for the closure disc such as disc 38 or 98 to release pressure in the interior of the container at the lower possible value which allows adequately for normal handling of the container and charge prior to ignition of the container contents.

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It will be appreciated that Figure 4 is provided by way of example only. Different combustible materials may have substantially different burning rate characteristics. Further, the point on the characteristic at which the container must be vented and the subsequent behaviour of the burning rate characteristic may be dependent upon the physical construction of the storage apparatus. A stronger apparatus, with better thermal insulation 15 for the individual containers, can accept venting at a higher pressure, for a given burning rate characteristic, than a lighter apparatus with poorer thermal insulation. Further, the speed of reaction of the venting system will also be relevant. If the combustion gases can be vented quickly, then the venting pressure may be at a higher location on the curve than if a substantial time is required to vent combustion gases with a consequent increased risk of pressure building up to the explosive condition.

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The invention is not limited to details of the illustrated embodiments. For example, in the embodiment illustrated in Figure 1, there may be a non-return valve in the opening 30, or in the duct connected with it in use. It may be preferable to provide a domed end plate 22 in place of the flat end plate, the concave surface of the dome facing inwardly of the storage apparatus. This will provide a stronger end wall for the apparatus, 25 and will also assist in directing combustion products towards the opening 30 which may be provided at the apex of the dome. As described in Figure 3, it may be preferred to locate the rim structures 42 of the containers shown in Figure 1 against an internal surface on the end plate 24 instead of on the axially outer surface as shown.

30 In any embodiment, any one or more of the containers may be designed to receive a plurality of separate bodies of propellant, with suitable separator barriers between them if required. If these bodies are spaced axially of the container, suitable means, for example a compression spring, may be provided to urge the charges towards the access means as individual charges are removed from the container. It is preferred that the exterior of each tubular wall in the storage apparatus is at least rounded, and preferably circular. This 35 will assist in deflection of any fragments striking the wall, reducing the chances of penetration. It will also assist the wall to contain internal pressure. The description has referred to the use of glass fibre filaments. Alternative fibres, preferably of similar tensile strength and tensile modulus ma be used in place of glass fibre, for example polyamide fibres sold under the trade mark KEVLAR. In place of continuous filaments, other windable elements such as strands, rovings, threads and yarns may be used. If required, indicator 40 means may be provided at or about the access portion of the storage apparatus to indicate that contents of an individual container have been ignited.

The present invention can be used in storage of any material the burning rate of which can be controlled by the venting system built into the apparatus. This will cover bagged propellants and propellant in combustible 45 cases. Propellant charges located in rigid cases can also be stored in the apparatus provided the case itself does not prevent the apparatus controlling the propellant burning rate.

What we claim is:

50 1 A storage apparatus for storing combustible material, the apparatus comprising a plurality of mutually isolated, closed compartments for containing said material, each compartment having a removable closure to enable access to be had to the interior of each compartment and additionally having compartment venting

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compartments, from said one or more compartments to a zone remote from each closure, the venting means being arranged to vent the combustion gases when the pressure thereof in a compartment exceeds a predetermined minimum value.

5 2 Apparatus as claimed in Claim 1 wherein the compartments are constituted by a plurality of containers mounted, in predetermined spaced relationship, in a housing.

3 Apparatus is claimed in Claim 2 wherein each compartment venting means is arranged to vent said gases into the housing and the housing itself is provided with housing venting means for venting said gases

10 from the housing to a zone remote from each said closure.

4 Apparatus as claimed in any one of Claims 1 to 3 wherein each compartment venting means comprises blow out means which will open up a venting passage for combustion gases within the container in the event that said gases exceed said minimum pressure.

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5 Apparatus for storing combustible material, the apparatus comprising a housing having side walls and two opposed end walls, a plurality of mutually isolated, closed, elongate containers mounted in the housing, an end of each container being sealingly secured in one and the same end wall of the housing, each said end having a removable closure to enable access to be had to the interior of each container from outside the

20 housing, and the other end portion of each container having venting means for venting combustion gases, produced in the event of combustion of said material in one or more containers, from said one or more containers each container venting means being adapted to vent the combustion gases when the pressure thereof in a container exceeds a predetermined minimum value.

25 6 Apparatus as claimed in Claim 5 wherein each container venting means is arranged to vent combustion gases into the housing and the housing itself is provided with housing venting means for venting combustion gases therefrom to a zone remote from said one end wall of the housing.

7 Apparatus as claimed in Claim 6 wherein the housing venting means comprises one or more apertures 30 in the other end wall thereof.

8 Apparatus as claimed in any one of Claims 2,3 and 4 when appendant to Claim 2 and 5 to 7 wherein each of said containers is tubular.

35 9 Apparatus as claimed in any one of Claims 1 to 8 the wall(s) of each compartment or container comprise(s) at least one layer of elastomeric material to provide at least a degree of self sealing and thermal insulation.

10 Storage apparatus substantially as hereinbefore described with reference to, and as illustrated in, Figure 40 1, Figure 2 or Figure 3 of the accompanying drawings.

BAE SYSTEMS PLC, Group IP Department, Lancaster House, PO Box 87, Farnborough Aerospace Centre, Farnborough, Hampshire, GUI4 6YU

DIVISION A5

1605450 Apparatus for Storing Combustible Materials IMI KYNOCH LIMITED [31 January 1977], 16828/77 Heading A5A [Also in division F3-4]

Combustible material, eg gun propellants, is stored in an apparatus comprising a plurality of mutually isolated closed compartments 34, each compartment having a removable closure 48 to provide access and a venting means,eg., disc 38, to vent combustion gases produced by any combustion of the contents of the compartment to a zone-remote from the closure when the pressure in the compartment exceeds a certain valve. The plurality of compartments is preferable mounted in a housing, eg 20, in a predetermined arrangement and the housing is provided with venting means, eg 30, to vent the housing to a zone-remote from the closures of the compartments. As shown in the drawing, the compartments 34 are mounted having one end in the same wall of the housing 20 each one end having a removable closure, the other respective ends having the venting means. The walls of the compartments 34 and the housing 20 may be self sealing and constructed of a composite laminate of elastomer and glass fibre reinforced plastics material.

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DIVISION F3

1605450 Apparatus for Storing Combustible Materials IMI KYNOCH LIMITED [31 January 1977], 16828/77 Heading F3A [Also in division A5-6]

Combustible material, eg gun propellants, is stored in an apparatus comprising a plurality of mutually isolated closed compartments 34, each compartment having a removable closure 48 to provide access and a venting means,eg., disc 3 8, to vent combustion gases produced by any combustion of the contents of the compartment to a zone-remote from the closure when the pressure in the compartment exceeds a certain valve. The plurality of compartments is preferable mounted in a housing, eg 20, in a predetermined arrangement and the housing is provided with venting means, eg 30, to vent the housing to a zone-remote from the closures of the compartments. As shown in the drawing, the compartments 34 are mounted having one end in the same wall of the housing 20 each one end having a removable closure, the other respective ends having the venting means. The walls of the compartments 34 and the housing 20 may be self sealing and constructed of a composite laminate of elastomer and glass fibre reinforced plastics material.