WO2001022430A1

WO2001022430A1 - A protective casing

Info

Publication number: WO2001022430A1
Application number: PCT/GB2000/003485
Authority: WO
Inventors: John Willetts; Howard Grant Whittaker; Graham Nicholson; Arthur Robin Mableson
Original assignee: British Nuclear Fuels Plc
Priority date: 1999-09-18
Filing date: 2000-09-11
Publication date: 2001-03-29
Also published as: EP1212757A1; AU7028200A; GB9922019D0; JP2003510581A; KR20020035141A; CN1375106A; BR0014095A; CA2384346A1

Abstract

A casing for the protection of an article contained within the casing is described, the protective casing comprising: at least two casing members which are assemblable to constitute a casing having an internal volume to receive the article, each of said at least two casing members comprising; an outer skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; an inner skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; a filling of a low density core material in a space between the outer and inner skin members; sealing means disposed in the joint face between said at least two casing members; and fastener means to hold said at least two members together the casing further comprising at least one metal insert on the inner skin.

Description

A PROTECTIVE CASING

The present invention relates to a removable protective casing for the protection of heavy and possibly hazardous articles during storage and/or transit. The protective casing is suitable for the protection of heavy containers of hazardous substances and particularly, though not exclusively, for the protection of cylinders of uranium hexafluoride in transit .

Gaseous uranium hexafluoride is the primary material from which nuclear fuels are made and is transported around the world in pressurised cylinders which are currently protected by a so-called "overpack" . The present protective overpack comprises stainless steel inner and outer skins having a filling of a phenolic resin or polyurethane foam in the intervening space between the skins . Due to the hazardous nature of the material being transported, the overpacks have to withstand rigorous tests set by regulatory bodies to ensure integrity if they are dropped from a height during handling for example and have also to provide a heat barrier and watertight protection for the contained cylinder. A 30" diameter cylinder full of uranium hexafluoride and having the overpack described above may weigh up to 4000kg. The overpack and cylinder must survive being dropped from 9m without damage to the cylinder. However, in some recent tests, deformation of the cylinder skirt and consequent damage to the cylinder valve through which the uranium hexafluoride is filled and removed has occurred. This has necessitated a complex, costly and difficult to fit valve protection member being added to the existing overpacks . The problems are exacerbated by corrosion of the overpack metal skins which allows the interior foam to become saturated with water making the overpacks even heavier and the absorbed water further increasing the corrosion rate in addition to that caused by the phenolic resin itself as the packs have to stay outside under virtually all climatic conditions. To further strengthen the present overpack, more metal components have been added which degrades the fire resistance due to increased thermal conductivity.

It is an object of the present invention to provide a protective casing which is lighter in weight, more durable and more easily repaired than the presently known overpack. It is a further object to provide a protective casing where no additional components to protect the valve of a contained cylinder are required.

It is a yet further object to provide a protective casing having improved resistance to corrosion and weathering. It is a still further object to provide a protective casing having improved fire resistance.

According to one aspect of the present invention there is provided a casing for the protection of an article contained within the casing, the protective casing comprising: at least two casing members which are assemblable to constitute a casing having an internal volume to receive the article, each of said at least two casing members comprising; an outer skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; an inner skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; a filling of a low density core material in a space between the outer and inner skin members ; sealing means disposed in the joint face between said at least two casing members; and fastener means to hold said at least two casing members together, the casing further comprising at least one metal insert on the inner skin.

The insert may be in the form of a metal ring bonded to the surface of the inner skin. The insert is for the purpose of supporting and distributing the forces resulting when the container and article are dropped from a height. Where the article is a uranium hexafluoride container generally in the form of a right cylinder, the localised stresses imposed by an end of the cylinder on impact may be sufficient to damage the inner skin of the casing if the supporting insert member is absent.

Preferably the insert is of a corrosion resistant metal such as stainless steel for example.

Preferably there are inserts at each end of the casing.

The insert may be substantially flat in cross section or may be any other suitable shape such as will deform to absorb forces consequent upon impact and spread such forces over the fibre reinforced plastics material. The plan view shape of the insert may correspond to the internal shape of the casing and/or to the shape of the relevant part of the article contained.

The insert may cover nearly all of the relevant face area of the inner skin.

The insert may be contained within the skin structure, ie within the plurality of layers of reinforcing fibres.

According to a second aspect of the present invention there is provided a casing for the protection of an article contained within the casing, the protective casing comprising: at least two casing members which are assemblable to constitute a casing having an internal volume to receive the article, each of said at least two casing members comprising; an outer skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; an inner skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; a filling of a low density core material in a space between the outer and inner skin members ; sealing means disposed in the joint face between said at least two casing members; and fastener means to hold said at least two members together wherein said fastener means comprises a pair of axially aligned sleeve members held in flange portions of said at least two casing members, said pair of sleeve members each having a locking pin member extending thereinto to connect said at least two casing members together. The flange portions are associated with the split-line region between casing members.

Preferably there are a plurality of fastener means along each axially directed edge of the casing.

The sleeve members may have a cross sectional shape of ^v top-hat' form with a flange at one end, the flange portion serving to spread the clamping forces and also provide a means of fixing the sleeve member to the casing member .

One of the sleeve members may have a substantially plain bore whereas the other co-operating sleeve member of the pair may be threaded to receive a threaded locking pin member.

The locking pin member may have a hinged integral handle member. Alternatively, the locking pin member may have suitable drive means such as a hexagonal head or an Allen key head for example to allow tightening by a separate tool .

The axial length of the sleeve members may be used to determine the maximum degree of closure of the casing members or desired degree of compression of sealing members .

The fastener means may also be provided with a compressible resilient member to allow an integral tightening handle member always to be positioned in a suitable desired position.

The fastener means according to the present invention may be mechanically fixed to the casing member to allow for repair or replacement of damaged fasteners.

The filling of low density core material is to provide an increase in the section modulus and to provide a crush zone in the event of impact.

Preferably, there are two casing members of generally semi -cylindrical form and the assembled casing may be of generally cylindrical form.

The casing members may not necessarily be of identical shape or construction.

Preferably, the outer casing skin comprises a plurality of layers of non-woven glass cloth and optionally aramid fibre layers having a matrix of a urethane acrylate, vinyl ester resin and/or polyester resin for example.

Preferably, the inner casing skin comprises a plurality of layers of non-woven glass cloth layers having a matrix of a polyester resin for example or the resin used in the outer casing skin.

However, other resin matrices such as epoxy or phenolic may be used in some applications. The non-woven cloths may be 0°/90° or 45°/45° or may be a mixture of both for example.

Woven cloths, continuous filament or chopped-strand mat may also be used in some applications.

The different fibre layers may be arranged alternately or in groups of two for example.

The inner and outer skins may each have an overall thickness in the range from about 2mm to about 25mm.

The outer skin may also incorporate external ribbing to increase strength and stiffness of the casing members. The recesses in the external ribbing may also provide convenient protection for fasteners used to lock the casing members together.

The protective casing of the present invention may also be provided with features which ensure that the contained article, eg a uranium hexafluoride cylinder can only be fitted within the casing in one position. Such features may comprise dowels or spigots which ensure that the casing members may only be fitted together in a unique manner and also internal features of the inner skin which will allow location of the article in a single orientation.

The low density core material between the inner and outer skins may be a PVC or polyurethane foam material or timber-based such as cork or balsa wood for example. In the case of foam, the core may have fillers such as glass spheres for example to reduce the density of the foam.

A foam core in the region of the joint faces between the casing members may be a high density syntactic foam for example to increase the strength in this region. Alternatively, another material such as wood may be used in this region if necessary.

The foam may itself be reinforced with various fillers such as clay, glass or ceramics for example. Glass fillers may also incorporate neutron or radiation shielding materials.

The foam may be introduced in the form of a liquid and foamed in-situ or may be in sheet form, curved by the application of heat and bonded to the facing surfaces of the inner and outer skins by an adhesive. Alternatively, the foam core may be cut from block material .

The thickness of the foam core may lie in the range from about 10mm to about 200mm.

The inner surface of the outer skin may have reinforcements bonded or otherwise incorporated to allow for the attachment of components by bolting, for example, to the outside of the casing. Such reinforcements may comprise materials such as wood or metals such as steel for example. Such components may include cradle members to allow for the convenient stacking and handling of the casing and contained cylinders during transportation and storage .

Corners of the protective casing may also further include reinforcing members such as additional layers of fibres and resin and/or embedded metal members. However, in order to maximise the fire resistance of the casing according to the present invention, the inclusion of metal members is desirably reduced to a minimum.

The faces of the casing members which constitute the joints therebetween may be provided with seal members to prevent ingress of water or other undesirable fluids.

The joint faces may also be provided with intumescent seals which expand when subjected to heat to further protect the enclosed article.

The outside of the casing in the joint region for example may be provided with an additional protective layer comprising, for example, a coating of a rubber to further improve abrasion and impact resistance.

A part of or the entire outer surface of the casing may be coated with a resilient coating such as polyurethane for example to further improve resistance to impact damage and absorb and distribute forces .

It has been found that the strength of the protective casing according to the present invention is sufficient to meet all the test procedures for cylinders of uranium hexafluoride for example at a significantly lighter overall weight than the presently used overpacks.

The method of manufacture may be by resin transfer moulding or resin infusion. Resin infusion and resin transfer (RTM) are processes where resin is injected into a fibre filled cavity between two mould surfaces.

Alternatively, the method of manufacture of protective casings according to the present invention may be by conventional laying up of layers of reinforcing fibres sequentially in a mould and impregnating with the appropriate resin followed by curing for example.

Casings of the present invention may be easily repaired unlike known overpacks for example. Furthermore, items subject to wear such as seals, fasteners, support inserts and the like may be easily replaced due to being adhesively or mechanically fixed to the casing members.

In order that the present invention may be more fully understood, examples of protective casings for the protection of uranium hexafluoride cylinders will be described by way of illustration only with reference to the accompanying drawings, of which:

Figure 1 shows a view in elevation of a uranium hexafluoride cylinder to be protected by the casing of the present invention; Figure 2 shows a side view in elevation of a protective casing according to the present invention;

Figure 3 shows an axial cross section on the line 3-3 of Figure 4 ;

Figure 4 shows a simplified end view of the casing of Figure 2 in the direction of the arrow "A" ;

Figure 5 shows a cross section of part of the joint face region between two casing members on the line 5-5 of Figure 2 ;

Figure 6 shows a plan view of a support insert as shown in Figure 3 ;

Figure 7 shows a view of a fastener arrangement according to the present invention where two casing members are to be secured together in the direction of the arrow ""B" of Figure 4;

Figure 8 shows the same view as in Figure 7 but with the casing members secured together;

Figure 9 shows a cross section through the fastener and part of the casing members of Figures 7 and 8 on the line 9-9 of Figure 2;

Figure 10 shows a plan view of the fastener of Figures 7, 8 and 9 in the direction of the arrow "C" of Figure 8; and Figure 11 which shows a schematic representation of a casing according to the present invention having features which permit a UF₆ cylinder to be contained in a single orientation.

Referring now to the drawings and where the same features are denoted by common reference numerals.

Figure 1 shows an elevation of a uranium hexafluoride cylinder 10. The cylinder comprises a welded metal shell 12; closures 14, 16 at each end and two metal skirts 18, 20, the skirt 18 enabling the cylinder to be stood up on end and also protecting a plug 22. The skirt 20 is primarily to protect a valve 24 through which the cylinder 10 is both filled with uranium hexafluoride and through which the same is extracted. If the valve 24 is damaged or knocked off, the cylinder contents may escape. With existing protective casings, recent occurrences have shown the skirt 20 to be deformed after dropping of the cylinder in the casing such that the skirt 20 has impinged on the valve 24 causing deformation thereof and a potentially dangerous situation. This has necessitated a complex, expensive and difficult to fit valve protection member (not shown) to be fitted to these cylinders when used with existing prior art overpacks to obviate damage to the valve.

A protective casing according to the present invention is shown generally at 40. The casing is generally cylindrical in shape and comprises two generally semi- cylindrical casing members 42, 44. The lower casing member 42 has two cradle members 46, 48 which support the casing 40 and contents 10 on the ground or on a transporter vehicle (not shown) . Each casing member has a flange portion 50, 52 running along the axial length on each side, the flange portions 50, 52 having therein a plurality of fasteners 60 to secure the casing members 42, 44 together and which will be described in greater detail below. The cradle members 46, 48 are provided with hard point plates 64, 66 on each side to which lifting means such as rings 68, 70 may be fitted for handling of the casing and contents. The casing and contents may alternatively be lifted and manoeuvred by the insertion of lifting forks of a truck (not shown) in the apertures 72, 74 formed between the cradle members and casing member 42. Figure 3 shows a cross section of the casing 40 on the line 3-3 of Figure 4. A contained uranium hexafluoride cylinder is indicated by the dashed line 10. Each casing member 42, 44 comprises an outer skin 80 and an inner skin 82 which are bonded together in the joint face region 84 by layers of fibre cloth impregnated with resin. The skins 80, 82 each comprise a plurality of layers of fibre cloth overlaid one upon the other and impregnated with a plastics resin material. In the embodiment shown, the outer skin 80 comprises:

a gelcoat and 450 csm;

8 layers of 0°/90° non-woven glass reinforcement, each layer alternating with;

8 layers of ±45° non-woven aramid reinforcement; with a polyester resin matrix. The inner skin 82 comprises:

5 layers of 0°/90° non-woven glass reinforcement, each layer alternating with; 5 layers of ±45° non-woven glass reinforcement; and a polyester resin matrix; and 450 csm and gelcoat.

The casing skins 80, 82 are produced by a resin transfer moulding system. The end portions 90, 92 of the outer skin and end portions 94, 96 of the inner skin are thicker in section than the central portions 98, 100 due to additional layers of glass reinforcement. Between the inner and outer skins is a core 86 of CNC cut, high density polyurethane foam material. Elastomeric rings 102 are provided around the inner periphery of the inner skin for seating the contained cylinder 10. A support insert 110 of stainless steel is both bonded to the inner skin at the axial transverse ends 112, 114 of each casing member and also fastened by mechanical means, in this case, fixing screws (not shown) . As may be seen from Figure 6, the support insert 110 comprises two members 130, 132 which are of different shapes, being non- symmetrical to each other. Each member 130, 132 has fixing plate extensions 136, 138 having holes 140, 142 for receiving fixing screws to hold the members 130, 132 to the inner skin. The support insert 110 is substantially flat so as to enable it to deform and absorb the impact forces generated by dropping of the casing and container, for example, and also to spread the forces more evenly to the material of the inner skin. The joint face region 84 is provided with sealing members 120, 122, either or both of which may be intumescent seals and which may be seen most clearly in Figure 5. The outer surface of the outer skin 80 is further provided with a polyurethane coating 126 on the ends of the casing members, however, the coating may be applied over the entire outer surface if desired.

Figures 7 to 10 show a fastener arrangement according to the present invention. As may be clearly seen from Figure 9, the fastener 60 is located in the flange portions 50, 52 of the casing members. There are a plurality of fasteners 60 distributed along the flange portion on each side of the casing members. Each fastener comprises a first sleeve portion 152 secured to one flange portion; a second sleeve portion 154 secured to another flange portion and in axial alignment with the first sleeve portion; and, a locking pin member 156 having a hinged handle 158. Each of the first and second sleeve portions have a flange member 160, 162 having threaded holes 166, 168 to receive fixing screws 170, 172 which pass through reinforcing plates 176, 178 let into a recess in the opposing face of the relevant casing flange portion. The first sleeve portion has a mainly clearance bore 180 to enable a threaded end 182 of the locking pin member 156 to pass therethrough. However, the end 184 of the first sleeve member has a few threads to enable the locking pin to be retained in the first member when the fastener 60 is undone. The length of the threaded portion 182 of the locking pin is less than the remaining unthreaded length of the first sleeve member. The second sleeve member 154 is provided with an initial unthreaded lead-in portion 188 and a threaded portion 190 to engage with the threaded portion 182 of the locking pin 156 to enable the casing members 42, 44 to be drawn together and secured as shown in Figure 8 by means of turning the hinged handle 158. A resilient Belville (trade name) washer 194 is provided to allow some latitude in the degree of rotation of the handle position to enable it to lie substantially parallel to the casing axis 200 when fully secured and in clips 196 provided for the purpose (see Figure 2) .

The fastener 60 need not be secured by means of threads on the locking pin and sleeve members but may have other known features such as bayonet connectors, for example, to effect locking together.

Figure 11 shows a schematic cross section of a protective casing 300 containing a UF₆ cylinder 10 (shown in part only) . The lower casing half 302 has a spigot 304 which mates with a hole (not shown) in the upper casing half 306 so as to ensure that the upper and lower casing members can only be assembled in a single relative orientation about the split line 308. The upper casing member 306 is also provided with protrusions 310 which will only allow the cylinder 10 to be inserted with the valve 24 at the protrusion end. The protrusions 310 may be moulded into the inner skin or be affixed thereto, for example. The spigot 304 and receiving hole may be located on the flange portions 50, 52 described with respect to Figures 2 to 10. The protective casings according to the present invention meet all Regulatory Body tests and do not require the valve protection member of prior art protective casings to be used thus, saving costs and resources.

Claims

1. A casing for the protection of an article contained within the casing, the protective casing comprising: at least two casing members which are assemblable to constitute a casing having an internal volume to receive the article, each of said at least two casing members comprising; an outer skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; an inner skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; a filling of a low density core material in a space between the outer and inner skin members; sealing means disposed in a joint face region between said at least two casing members; and fastener means to hold said at least two casing members together, the casing further comprising at least one metal insert on the inner skin.

2. A protective casing according to claim 1 wherein the at least one metal insert is to distribute forces generated in an impact to said casing.

3. A protective casing according to either claim 1 or claim 2 wherein the insert is in the form of a metal ring bonded to the surface of the inner skin.

4. A protective casing according to any one preceding claim wherein the insert is made of a corrosion resistant metal .

5. A protective casing according to any one preceding claim wherein there are inserts at each end of the casing.

6. A protective casing according to any one preceding claim wherein the insert is substantially flat in cross section.

7. A protective casing according to any one preceding claim wherein the plan view shape of the insert corresponds to the internal shape of the casing and/or to the shape of the relevant part of the article contained.

8. A protective casing according to any one preceding claim wherein the insert covers nearly all of the relevant face area of the inner skin.

9. A protective casing according to any one preceding claim wherein the insert is contained within the plurality of layers of reinforcing fibres.

10. A protective casing according to any one preceding claim wherein the insert is mechanically fixed to the inner skin.

11. A casing for the protection of an article contained within the casing, the protective casing comprising: at least two casing members which are assemblable to constitute a casing having an internal volume to receive the article, each of said at least two casing members comprising; an outer skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; an inner skin of fibre reinforced plastics material having a plurality of layers of reinforcing fibres in a plastics material matrix; a filling of a low density core material in a space between the outer and inner skin members; sealing means disposed in the joint face between said at least two casing members; and fastener means to hold said at least two members together wherein each fastener means comprises a pair of axially aligned sleeve members held in flange portions of said at least two casing members, said pairs of sleeve members each having a locking pin member extending thereinto to connect said at least two sleeve members, and hence said casing members, together.

12. A casing according to claim 11 wherein the sleeve members have a cross sectional shape of ^Λ top-hat' form with a flange at one end.

13. A casing according to either claim 11 or claim 12 wherein the sleeve flange portion serves to spread clamping forces and also provides a means of fixing the sleeve member to the casing member.

14. A casing according to any one of preceding claims 11 to 13 wherein one of the sleeve members has a substantially plain bore whereas the other co-operating sleeve member of the pair is threaded to receive a threaded locking pin member.

15. A casing member according to any one of preceding claims 11 to 14 wherein the locking pin member has a hinged integral handle member.

16. A casing member according to any one of preceding claims 11 to 14 wherein the locking pin member has suitable drive means such as a hexagonal head, or an Allen key head, or a splined form to allow tightening by a separate tool .

17. A casing member according to any one of preceding claims 11 to 16 wherein the axial length of the sleeve members is used to determine the maximum degree of closure of the casing members or desired degree of compression of sealing members.

18. A casing member according to any one preceding claim from 11 to 17 wherein the fastener means is provided with a compressible resilient member to allow an integral tightening handle member always to be positioned in a suitable desired position.

19. A casing according to any one preceding claim from 11 to 18 wherein the fastener means are mechanically fastened to the casing members to allow for repair or replacement of damaged fasteners.

20. A protective casing according to any one of preceding claims 1 to 9 wherein the insert is in at least two pieces .

21. A casing according to claim 20 wherein the pieces are of different shapes.

22. A protective casing according to any one preceding claim wherein the casing members have means to ensure that they can only be joined together in one relative orientation.

23. A protective casing according to claim 22 wherein said means comprises spigots and spigot receiving holes.

24. A protective casing according to any one preceding claim further including means to ensure that said article can only be contained in a predetermined orientation within said protective casing.

25. A protective casing according to claim 24 wherein said means comprises features on said inner skin which co-operate with features on said article.