GB2024796A - A melting vessel for explosives - Google Patents

Abstract

A melting vessel for explosives is provided with an internal agitator and has inside walls formed as an array of hollow ribs for receiving the flow of a heat transfer medium. In a preferred embodiment, the vessel has outer and inner jackets, and the inner jacket wall is folded in wave like manner to form hollow ribs which constitute separate channels for the heat transfer medium.

Description

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GB 2 024 796 A

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SPECIFICATION

A melting vessel for explosives

5 The invention relates to a melting vessel for explosives, comprising an agitato in the interior of said vessel and having cavities formed in the side wall and, if desired, in the bottom for the passage of a heating medium by means of which the explosive 10 melt in the interior is adapted to be tempered indirectly.

Such a melting vessel serves for preparing molten explosives at casting temperature. The explosive is processed out of the melting vessel, e.g. by casting 15 into projectile bodies. The melting vessel is fed with at least partly molten explosive which has previously been fused in another upstream apparatus. If desired, solid explosives are added in the melting vessel. These solid explosives may be available, for 20 instance, in the form of granules, flakes or pieces and are converted into the molten state in the melting vessel. By lowering the temperature, the resulting explosive melt is brought down to casting temperature which has a very close tolerance for the sol-25 idification temperature of the melt. In this context, as little as 1 to 2 degrees Celsius are critical. The heat required for melting the added solid explosive is supplied at least in part by way of the heating medium, which moreover, serves for general tempe-30 ring of the melting vessel.

It is a requirement of the respective safety regulations that apparatus for melting and tempering explosives should not have any separate heating elements in the interior. Therefore, the tempering is 35 effected indirectly by means of the cavities formed in the side wall and, if desired, also in the bottom. Moreover, the safety regulations restrict the maximum difference between the temperature of the heating medium and the fuson temperature of the 40 explosive to a relatively low value of a few degrees Celsius only. In combination with the usually smooth interior of the side walls of known melting vessels this provides only a small melting capacity. Furthermore, quick adjustment of the explosive melt to 45 the casting temperature by means of the heating medium is impossible.

It is, therefore, the object of the invention to develop a melting vessel of the kind mentioned above which is such that a high efficiency in consid-50 eration of the safety requirements and a quick adjustment of the explosive melt to casting temperature are rendered possible.

This object is met, in accordance with the invention, in that the side wall comprises a plurality of 55 hollow ribs which face into the interior and through which the heating medium flows.

In the melting vessel according to the invention the ribs provide a distinct enlargement of the area through which the explosive may enter into a heat-60 exchange relationship with the heating medium.

This makes it possible to supply to the melt or to dissipate therefrom relatively large quantities of heat in a short time, even at small temperature differences between the heating medium and the explo-65 sive melt. Consequently, the melting efficiency is high and the explosive melt is adjusted quickly to the temperature which is predetermined by the heating medium. The ribs have another advantageous effect in that they act like "wave breakers" with respect to the explosive melt which is stirred by the agitator. In this way they guarantee a particularly intimate and especially quick thorough mixing of the melt throughout. As the heat conductively of explosives is poor, this contributes to the quick heat transfer between the explosives melt and the heating medium. It further warrants an even temperature distribution throughout the explosive melt without the formation of any temperature gradients worth mentioning, in particular also close to the side wall. The latter circumstance permits an active quick cooling of the explosive melt down to casting temperature by means of the heating medium which in this case acts as a cooling medium relative to the melt. It does not involve any risk of an incrustation by solidified explosive on the side wall of the melting vessel. The period of time until casting temperature is reached is shortened drastically as compared with the natural cooling practised so far which took for example about two hours, whereas now it lasts only 10 to 15 minutes. Finally, in combination with suitable temperature control of the heating medium, it is even possible with the novel melting vessel to keep a pure explosive melt which begins to become crystallised at casting temperature for several hours without any thermally caused change taking place in the melt. Thus, the further processing of the melt may last for a longer period of time without causing any problems.

Conveniently, the ribs each define a separate channel forthe heating medium because this.pro-videsfor even better uniformity of the heat transfer between the heating medium and the explosive melt.

In a preferred embodiment of the novel melting vessel, the side wall is made of a smooth outer jacket and of an inner jacket which is folded into the form of ribs. It is best for the inner jacket to be folded in the form of waves and to have the outer wave crests closely abuting against the outer jacket. This particular design greatly facilitates the manufacture of the novel melting vessel. Besides, a particularly large inner surface is obtained as compared with the outer surface of the side wall and this, of course, is favourable forthe speed of the heat transfer.

Atriangular cross-section has proved to be favourable especially with a view to the function as "wave breakers". Apart from this, of course, other cross-sectional shapes may be chosen, e.g. a semi-circular cross section.

It is also conceivable that the ribs in the interior of the melting vessel might extend in different directions. Preferably, their direction is so selected that the ribs will extend parallel to the main direction of flow of the explosive melt at the side wall produced by the agitator. This is the most effective in preventing that the agitator should simply rotate the entire melt without, at the same time, giving it a thorough internal mixing. Furthermore, in this event, the explosive melt is guided along the ribs at the greatest possible speed and in a homogeneous flow in the

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region of the ribs. This again has a favourable effect on the speed of the heat transfer.

In the case of the preferred embodiment of the novel melting vessel, these latter aspects are 5 allowed for in that the agitator is provided with propeller blades on a vertical shaft and that the ribs extend in a vertical direction.

The melting vessel according to the invention is destined in particular for treating trinitrotoluene 10 (TNT) or mixtures of TNT and trimethylene-triammine, TNT and nitrate of ammonium or TNT/trimethylene - triammine/aluminim.

The invention is now described further, by way of example, with reference to the accompanying draw-15 ings, in which:

Fig 1 is a diagram matic elevation of a plant for melting explosives, comprising a melting vessel according to the invention;

Fig. 2 is a vertical sectional view of the melting 20 vessel according to fig. 1 upon removal of the lid;

Fig. 3 is a section along the line 3-3 in fig. 2;

Fig. 4 is a block diagram of a heating and cooling system forthe heating medium associated with the melting vessel.

25 As may be taken from fig. 1, a plant for melting TNT comprises an apparatus 1 for quick fusing of the TNT which is supplied in a solid condition and a heated collecting vessel 2 forthe molten TNT.

Molten TNT at a temperature within a permitted 30 range above the melting point is fed from the collecting vessel to a heated weighing device 3 which is connected to the collecting vessel 2 by way of a heated discharge stud 4. From the weighing device 3 a certain quantity of molten TNT is passed through a 35 heated stud pipe 5 into a melting vessel 6. A plurality of similar melting vessels may be connected to the weighing device 3.

The melting vessel 6 is filled with the fluid TNT melt up to 20 to 40% only based on its maximum 40 volume. The remainder of the TNT is then added in a solid condition, e.g. in the form of granules. This proportion is converted into the fused condition in the melting vessel 6. An agitator8 is disposed in the interior 7 of the melting vessel. The agitator is driven 45 by a motor 10 mounted at the lid 9 and constantly agitates the TNT melt.

The circular melting vessel 6 is heated indirectly at its side wall 11 and at the bottom 12 by means of a heating medium, such as water. The heat of fusion 50 forthe added solid TNT is taken not only from the heating medium but also from that proportion of TNT which was heated to above melting temperature and the temperature of which will thus be reduced. Any remaining difference in temperature 55 relative to the casting temperature is removed by using the heating medium for cooling. In this case, the heating medium acts as a cooling medium with respect to the TNT melt. The TNT melt which has thus reached the casting temperature and is main-60 tained at temperature is fed through a heated discharge pipe stud 13 for example to explosive bodies to be filled with TNT.

Details of the melting vessel 6 which is made of stainless steel may be taken from figs 2 and 3. The 65 side wall 11 consists of a smooth circular cylindrical outer jacket 14 and an inner jacket 15 which is continuously folded in the circumferential direction in the form of a triangular wave. The outer wave crests 16 or apices thus formed abut closely against the 70 outer jacket 14. Thus, a plurality of similar hollow ribs 17 are formed which each have a triangular cross-section and extend in the axial or vertical direction, are oriented towards the interior7 of the melting vessel 6 and each define a separate vertical 75 channel 18 for the; heating medium. An annular outer channel 19 is disposed along the peripheral edge of the bottom 12 which is slightly inclined downwardly toward the center. The annular channel communicated with each channel 18 through bores 20 in the 80 bottom 12. The annular outer channel 19 is further connected through a number of radial channels 21 to an annular inner channel 22 which surrounds a central connecting with a supply pipe 24 for the heating medium. An annular channel 25 corresponding to 85 the annular outer, channel 19 is disposed at the top of the melting vessel. It likewise communicates with the channels 18 by way of bores and furthermore with a discharge pipe 26 forthe heating medium. The heating medium is fed through the supply pipe 90 24, the annular inner channel 22, and the radial channels 21 to the annular inner channel 19 at the bottom and then rises through the channels 18 in the interior of the ribs 17 so as to be collected again in the upper annular outer channel 15 and leaves the 95 latterthrough the discharge pipe 26.

A lid 9 is fastened on a support 27 by means of three quick-acting closures 28. The agitator 8 has a vertical shaft 29 which extends parallel to the ribs 17 and on which three double-armed great propeller 100 blades 30 are fixed which reach almost up to the side wall 11. In this way, the TNT melt is agitated so that it is pressed down in the central area close to the axis of the vessel flows radially outwardly at the bottom and rises again at the side wall parallel to and bet-105 ween the ribs 17.

A heating and cooling system forthe heating medium, as shown in fig. 4, is coordinated with the melting vessel 6. It consists of a primary circuit 31 under coarse control with respect to the temperature 110 of the heating medium, and of a secondary circuit 32 under fine control. In the primary circuit, the heating medium which is circulated by a pump 33 is heated in a heat exchange 34 to which a vapour D is supplied. The coarse temperature control is effected by f 15 a control device 35 which is responsive to the temperature of the heating medium downstream of the pump 33 and acts on an adjustable element 36 at the vapour inlet of the heat exchanger.

The secondary circuit 32 extends from the primary 120 circuit 31 through a feed valve 37, a circulating pump 38, then through the melting vessel 6 in the above-described manner and back to the primary circuit 31. A branch leads from the return flow downstream of the melting vessel to the feed valve 37. A heat 125 exchanger 39 supplied with cooling air L from a blower 40 is connected in this branch. A pneumatic proportinal/integral control means 41 processes measuring signals supplied by a heating medium temperature sensor 42 in the forward flow and a hea-130 ting medium temperature sensor 43 in the return

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flow. In accordance with these measuring signals and a predetermined temperature of the TNT melt, the control means 41 influences the feed value 37 so that a certain temperature of the heating medium in

5 the channels of the melting vessel and thus the desired temperature of the TNT melt will result from the mixing ratio adjusted between the heated medium of the primary circuit 31 and the cooler heating medium from the heat exchanger 39.

10 Another secondary circuit 44 including a feed valve 45, a circulation pump 46, a control means 47, and a temperature sensor 48 branches off from the primary circuit 31. This secondary circuit serves to heat the outlet pipe stud 13.

Claims (8)

15 CLAIMS

1. A melting vessel for explosives, comprising an agitator in the interior of said vessel and having cavities formed in the side wall and, if desired, in the bottom forthe passage of a heating medium by

20 means of which the explosive melt in the interior is adapted to be tempered indirectly, the inside wall of the vessel comprising an array of hollow ribs which face into the interior and through which a heat transfer medium flows.

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2. A melting vessel as claimed in claim 1,

wherein the ribs each define a separate channel for the heat transfer medium.

3. A melting vessel as claimed in claim 1 or 2, wherein the side wall consists of a smooth outer

30 jacket and an inner jacket foled to form the ribs.

4. A melting vessel as claimed in claim 3,

wherein the inner jacket is foled in wave shape and the outer crests of the waves closely abut against the outer jacket.

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5. A melting vessel as claimed in one of claims 1 to 4, wherein the ribs each have a triangular cross section.

6. A melting vessel as claimed in any one of claims 1 to 5 wherein the ribs extend parallel to the

40 main direction of flow ofthe explosive meltatthe side wall generated by the agitator.

7. A melting vessel as claimed in claim 6,

wherein the agitator comprises propeller blades mounted on a vertical shaft, and in that the ribs

45 extend in vertical direction.

8. A melting vessel for explosive substantially herein described with reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1979.

Published at the Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.