WELD SHROUD

Abstract: A method and apparatus for welding workpieces in a hazardous environment comprises surrounding the vicinity of the weld region with a buffer zone. A fluid which is inert relative to the environment is provided in the buffer zone to shield the weld region. The fluid may be liquid or gas. The shroud may be used with any type of welding.

Description: WELD SHROUD This application relates to welding, in particular to welds made in a hazardous environment such as in working chemical plant or oil rigs. Traditionally the danger of explosion during welding in chemical plant or zoned areas of oil rigs means that whenever it is necessary to carry out welding in those areas the plant or the zoned area has to be shut down. This is expensive in terms of lost production time and in some cases start up and shut down can be more prone to danger than keeping the systems running. In accordance with one aspect of the present " invention, a method of welding workpieces in a hazardous environment comprises surrounding the vicinity of the weld region with a buffer zone containing a fluid which is inert relative to the environment so as to shield the weld region- from the environment. Typically water or an inert gas is caused to flow through the buffer zone although a static arrangement is also possible in some circumstances. The buffer zone may be separated from the,,weld area by the addition of an inner casing around the weld region inside the shroud. In accordance with a second aspect of the present invention a weld shield assembly comprises, a shroud .for surrounding the vicinity of a weld region of workpieces to be welded, the shroud having an opening to permit a weld tool to be connected to one of the workpieces, and being shaped so as to retain a fluid which is inert relative to the surrounding environment, whereby the fluid shields the weld region in use from the environment. Typically the fluid is an inert gas or water. Preferably the apparatus includes a seal for sealing the shroud to the weld tool to retain fluid in the shroud. Preferably, the assembly includes an inner casing which surrounds the weld region and which may be SUBSTITUTE SHEET independent from the shroud but preferably is an integral part of the shroud. Typically, the inner casing includes a layer of foam or other material which enhances the quality of the weld and separates the weld region from the fluid. Where there are dangerous gases, liquids or powders present the cavity formed between the shroud and the casing isolates the weld area, this isolation being improved by a flow of water or inert gas between fluid input and output apertures provided through the shroud. The weld shield assembly can be made of rigid metal or plastics materials or more flexible plastics materials chosen for the ability to withstand the temperatures they will be subjected to (typically up to 1100°C) . A combination of materials for the separate areas would be possible or else a rigid outer structure can be sealed to the weld surface by flexible joints, this would be more likely where the inner casing is an integral part of the shield assembly. The method and apparatus described above are suitable for any type of welding including arc welding, friction welding and flame welding. Some examples of shield assemblies and methods according to the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a cross-section through one example of a shield assembly in which the inner casing is an integral part of the shroud; Figure 2 illustrates a modification of the Figure 1 example; and. Figure 3 is a cross-section through another example of a shield assembly in which the inner casing is independent from the shroud. The shield assembly 9 shown in Figure l has a circular upper part 1 and depending cylindrical skirt 15 defining a shroud and made of aluminium, steel, stainless steel or the like provided with an input aperture 2 and output aperture 3 for an inert fluid. An inner casing 5 is integrally formed as an integral part of the shroud and makes contact with the weld surface 10 of a workpiece via flexible seal 11 similar to that by which the depending skirt 15 contacts the weld surface 10. A cavity 4 is formed between the inner casing 5 and outer portions 1, 15 of the shroud defining a buffer zone. The inner casing 5 keeps the weld region 8 separate from the area of danger and helps to prevent the escape from the weld area 8 into the area of danger of heat, sparks or ultraviolet radiation while the fluid flow through the cavity removes heat. A cylindrical neck 12 on the upper part 1 provides an opening for a weld tool 6 through which it can bring a workpiece 7 into contact with the weld region 8. There is a seal 13 provided between the neck 12 and the weld tool 6 to prevent flow of fluids between their surfaces or the egress of heat or sparks to the area containing dangerous materials. A block of closed-cell EVA type foam 14 is provided in the inner casing 5 to prevent the fluid reaching the weld region 8 while inlet and outlet apertures 16A, 16B are provided in the wall of the casing 5 to enable fluid to be present on top of the foam. In use, the shield assembly 9 is positioned over the region to be welded 8 without the weld tool 6, the weld tool 6 only being inserted through the neck 12 when the shield assembly 9 " is fixed in position. Alternatively the shield assembly 9 can be fixed onto the weld tool 6 and then the complete assembly positioned as required for a weld. An inert fluid such as water, nitrogen, argon or carbon dioxide is then caused to flow through the shroud and inner casing 5 (by means not shown) while welding takes place. Figure 2 shows a shield assembly similar to Figure 1 but with the inner casing 5 separate from the shroud. In this case the casing 5 is sealed to the shroud by a seal 17 and is mounted directly to the weld tool 6. Figure 3 shows a further example of a shield assembly 9. In this case the inner casing is omitted and the cavity 4 defined by the shroud and the foam 14.

Claims: CLAIMS 1. A method of welding workpieces in a hazardou environment comprising surrounding the vicinity of the wel region with a buffer zone containing a fluid which is iner relative to the environment so as to shield the weld regio from the environment. 2. A method of welding workpieces according to claim comprising surrounding the weld region with an inert gas. 3. A method of welding workpieces according to claim 1 o claim 2, further comprising causing fluid to flow past th weld area continuously. 4. A method of welding work-pieces according to any o claims 1 to 3, wherein the buffer zone is separated fro the weld region. 5. A weld shield assembly comprising a shroud fo surrounding the vicinity of a weld region of workpieces t be welded, the shroud having an opening to permit a wel tool to be connected to one of the workpieces, and bein shaped so as to retain a fluid which is inert relative t the surrounding environment, whereby the fluid shields th weld region in use from the environment. 6. Apparatus according to claim 5, in which the fluid i an inert gas. 7. Apparatus according to claim 5 or claim 6, in whic there are fluid input and output means and means to provid a constant flow of fluid past the weld area. 8. A weld shield assembly according to any of claims 5 t 7, in which the shroud is spaced from the weld area by a inner casing around the weld area outside which fluid i held in a cavity formed between the inner casing and th shroud. 9. Apparatus according to claim 8, in which the inne casing is formed by a layer of foam. 10. Apparatus according to claim 8, in which the inne casing is an integral part of the shroud.

Inventors: BLAKEMORE GORDON ROBERT, BLAKEMORE, GORDON, ROBERT
Applicants: RAMFORCE SERVICES LIMITED
Application year: 1991
Main classification: B23K9
IPC codes: B23K9