A fire protected steel structure, removable panels for fire protection of steel structures and a method of manufacturing fire protection panels

[0001] The present invention relates to a fire protected steel structure and removable claddings for fire protection of steel structures. The panes are intended to cover steel structures such as pipe elements, girders, tanks, flanges, valves, columns, claddings, walls and so on, especially for offshore installations, processing plants, vessels, or anywhere where metal structures remain in an environment where fire protection is a theme.

[0002] When there are fires in or near steel structures, it is very important that the structures are adequately fire protected so that functionality and ability to carry a load can be maintained. The steel structures may be of any shape, for example cylindrical, square, or they may be shaped as girders, columns or walls.

[0003] Fires that occur, for example, in hydrocarbon-producing or processing installations could threaten the structural integrity of the installation's load-bearing steel structures (girders / columns). Failure of a load-bearing steel structure on an installation could lead to significant damage to both personnel and equipment, and could lead to significant pollution.

[0004] Accordingly, it has been proposed to provide such installations with a form of passive thermal insulation which seeks to reduce the thermal loads on the structure in the event of a fire. When such fire insulation is tested, it should also be possible to document resistance to jet and hydrocarbon fires, fire and explosion loads.

[0005] Throughout the world, there are a number of requirements and standards for passive protection of steel structures in the event of fire and explosion. In most cases, a load-bearing steel structure should be able to withstand jet and hydrocarbon fires for 60 to 120 minutes without increasing the radiation temperature to 400 ° C. The steel structures should in most cases also be able to withstand an explosion pressure of up to 0.3 bar. A flame temperature in jet and hydrocarbon fires could well exceed 1300 ° C.

[0006] Examples of such standards include Norsok Standard S-001 N and R004, UL Standard Fire resistance Rating ANSI UL 263 and ANSI / UL 1709. The solution of the present invention meets these standards.

[0007] Current passive fire protection for load-bearing steel structures usually includes expandable fire-insulating epoxy materials or cement-based lightweight concrete. These substances are sprayed directly on the structure to be protected.

[0008] This solution has some obvious disadvantages. In order to be able to remove the fire-retardant substance from the structure, a chisel and chisel hammer must usually be used. Any tool (such as an angle grinder) that heats the fire-insulating fabric should not be used, as toxic hydrocyanic gases may be developed. Inspection of welding zones, corrosion damage, anti-corrosion coatings or any repair work or modifications becomes difficult when the protected structure is coated directly on the surface.

[0009] In places with high humidity, it is very difficult to use fire-insulating epoxy substances. Under these conditions, cement-based lightweight concrete is primarily used. However, aerated concrete that is sprayed is not impermeable, and absorbs moisture which in turn contributes to corrosion. Furthermore, concrete tends to deteriorate over time, reducing fire protection properties.

[0010] A problem when using epoxy-based substances is that high temperatures are required during application, and that the equipment used is not suitable for use in oil and gas installations due to the risk of fire and explosion. Essentially all passive fire protection on oil and gas installations is applied manually. There are also significant problems with fire-insulating epoxy substances expressed by HSE. Hazardous gases are released during application and during the time the epoxy hardens. This typically leads to epoxy allergy for staff, which thus prevents further work with epoxy.

[0011] It is an object of the present invention to provide a solution which meets the necessary standards, which does not promote corrosion, which does not absorb moisture, which has a reasonable weight, which allows inspection of the structure to be protected, i.e. light to manufacture, and which can be adapted for use on many structures and which can be used under all relevant climatic conditions. Furthermore, it is a goal to provide a solution with a service life of 25 years without having significant maintenance. It is also an object of the present invention to provide a system which can be installed without having to shut off the structure to be protected (for example an offshore platform) for use. Furthermore, it is an object to provide a system that can be installed despite an environment with an explosion hazard. The solution should also be able to satisfy all relevant HSE requirements within the relevant sectors, such as in the oil and gas industry.

[0012] An important feature of the invention is that, instead of applying the passive fire protection directly to the structure to be protected, prefabricated fire protection coverings are installed on the structure to be protected while maintaining suitable conditions regarding ventilation, temperature and humidity. The solution of the present invention includes claddings that are easy to remove, to facilitate inspection of, for example, welding zones, to control corrosion, cracks, deformations and corrosion protective coatings. The removable covers can also be adapted for a number of applications, and as they are easy to remove, it will be possible to attach various equipment, repair measures and modifications. The cladding can be installed in environments that are exposed to fire and explosion hazards without the need for explosion-proof equipment.

[0013] The epoxy layer used in the coatings of the invention will typically begin to expand when exposed to temperatures above 200 ° C. The layer typically expands by five times the original thickness when exposed to jet and hydrocarbon fires. It is this expanded epoxy layer that provides the thermal insulation in a fire. In order to allow this expansion, there should always be a distance between the protective coverings and the structure to be protected. The required distance will clearly depend on the thickness of the expanding layer. Fire protection requirements, the thickness of the protected material and the length of time requirements to maintain the integrity of the protected material are crucial in order to determine the thickness of the epoxy layer.

[0014] The claddings have very low heat-insulating properties before they are exposed to heat. This is beneficial since, ideally, the claddings have the same temperature on the inside and outside to prevent condensation on the structure so that corrosion is prevented.

[0015] The cladding joints should generally be open, but will be sealed again when the cladding begins to expand at higher temperatures.

[0016] The windows could, for example, be designed to withstand jet fires (gas fires) with a heat flux of 350 kW / m², which indicates temperatures well above 1300 ° C. The claddings have been tested for hydrocarbon fires with a radiant heat of 1100 ° C.

[0017] Accordingly, the present invention relates to a fire-protected steel structure comprising at least one fire-protective cladding covering the steel structure. For example, in the case of submerged beams and girders, only one coating may be sufficient. However, the protection includes several claddings for covering a structure, as will be shown in the drawings. All claddings include a perforated metal plate and an internally expanding fire protection layer having a thickness on one outside of the perforated metal plate. The fire protection layer extends through the perforated metal plate. Soluble mechanical fasteners are provided for removable attachment of the at least one fire protection cladding to the steel structure. The releasable attachment may be in direct attachment to the structure, or may be provided by claddings enclosing the structure. Preferably, the claddings are attached directly to the structure with screws, bolts and so on, and cladding joints are clamped together with suitable joining elements, such as clamps. [0018] The releasable mechanical fasteners may include a fastening nut and a threaded fastening rod secured to the steel structure.

[0019] The releasable mechanical fasteners can be covered with a heat-insulating fastener cover on an outside of the cladding, opposite to the steel structure. The fastener cover may be of a hat-shaped channel which can be screwed or pop-nailed to the cladding to be attached to the underlying structure.

[0020] The releasable mechanical fasteners may include clamping elements that are in an over-a-center position, or a combination of fastening nuts and threaded fastening rods.

[0021] A gap with a gap clearance may be provided between the steel structure and the fire protection covers, and the gap may be more than five times as large as the thickness of the internally expanding fire protection layer. However, the ideal gap clearance will depend on the rate of expansion of the expanding layer, and the gap clearance should be able to allow full expansion of the inner layer. However, it is difficult to provide full clearance everywhere due to blanks that apply to the attachment, but the claddings will still provide effective protection even if the claddings are in some places close to the underlying structure. The heat will also spread to colder areas, which thus reduces the heat load.

[0022] The fire-protected steel structure may further comprise a fastening element with tightening units to provide a holding force between the fastening element and the steel unit. The releasable mechanical fasteners will then be able to be fastened to the fastening element.

[0023] The at least one fire protection cladding may further include drainage holes to prevent accumulation of liquid inside the at least one fire protection cladding, where the drainage holes are sealed as the expanding fire protection layer expands in case of fire.

[0024] The drainage holes may be formed in an open mounting sleeve extending through the cladding. The bushing may include an inner layer of expanding fire protection material, which seals said open mounting bushing should a fire occur.

[0025] Ventilation ducts that prevent moisture accumulation can be made between the steel structure and the at least one cladding.

[0026] The invention further relates to a cladding for fire protection of a steel structure, which comprises a perforated metal plate and an inner protective layer having a thickness on one inside of the perforated metal plate and an externally expanding fire protective layer having a thickness on an outside of the perforated metal plate . The fire protection layers extend through the perforated metal plate and form a connection between the inner and outer layers.

[0027] A reinforcing element will be able to provide a support between the cladding and the steel structure in the event of an explosion.

[0028] Brief description of the accompanying drawings:

[0029] Fig. 1 is a perspective view of a fire-protected steel structure with some fire-protective claddings according to the invention;

[0030] Fig. 2 is a perspective view of a girder with fire protection coverings according to the invention;

[0031] Fig. 3 is a cross-sectional view of a detail of Fig. 2, showing a bushing;

[0032] Fig. 4 is a perspective view of a corrugated cladding with fire protection claddings according to the invention;

[0033] Fig. 5 is a perspective view of a detail of Fig. 4, showing a joint and a releasable fastener;

[0034] Fig. 6 is a cross-section of a flat portion, which is covered with fire-protective coverings;

[0035] Fig. 7 is a perspective view of a detail of Fig. 8, showing a joint;

[0036] Fig. 8 is a perspective view of a flat portion, which is covered with fire-protective coverings according to the invention;

[0037] Fig. 9 is a perspective view of a joint between different fire protection claddings;

[0038] Fig. 10 is a perspective view of a cylindrical or tubular portion and suitable fire protection claddings;

[0039] Fig. 11 is a perspective view of an H-shaped column covered with two U-shaped fire protection covers;

[0040] Fig. 12 is a perspective view of a detail of a typical over-a-center lock used in connection with the invention;

[0041] Fig. 13 is a perspective view of a rectangular duct section covered with two L-shaped fire protection claddings;

[0042] Fig. 14 is a cross-sectional view of a corner of Fig. 13;

[0043] Fig. 15 is a cross-section of an H-shaped girder with suitable L-shaped claddings according to the invention;

[0044] Fig. 16 is a side view of the height of the girder and cladding shown in Fig. 15;

[0045] Fig. 17 is a cross-sectional view of a detail of Fig. 15, showing fasteners and fastening covers;

[0046] Fig. 18 is a cross-sectional view of an alternative fire protection cladding for a partially submerged H-shaped girder;

Fig. 19

[0048] Fig. 20 is a perspective view of an L-shaped fire protection cladding, also showing support and reinforcement elements;

[0049] Fig. 21 is a cross-section of another fire-protective cladding, which is attached to an H-shaped girder with a fastening element;

[0050] Fig. 22 is a perspective view of the solution shown in Fig. 21; and

[0051] Fig. 23 is a perspective view of the fastening element.

[0052] Figure 1 shows a typical load-bearing structure, such as an offshore structure 2 which is composed of a combination of beams, girders and tubular support elements which in some places are protected with protective claddings according to the invention. The offshore structure is made of steel, and the fire protection claddings are designed to address issues related to fire protection, corrosion and inspection. Curved fire protection claddings 3 are shown fastened around two of the tubular supports, and channel-shaped fire protection claddings 1 are shown fastened to some of the columns. The fire protection claddings 1, 3 are fastened to each other in fire protection cladding joints 4. Each cladding should typically not exceed a weight of 25 kg. The fire protection claddings can also be specially designed for different purposes, and special constructions can be seen on the top and the lower end of the columns.

[0053] Figure 2 shows a detail in a perspective view of L-shaped, expanding, fire-protective claddings 1 which are joined in a fire-protective cladding joint 4 with locks 8. The locks 8 are typical clamping elements of type over-center position locks, which can typically be suitcase locks or similar. Figure 2 further shows a steel girder 7 which is protected with channel-shaped fire protection claddings 1 which are fastened to each other with locks 8 in the fire-protective cladding joint 4. The channel-shaped fire protection claddings 1 include explosion reinforcements 6 which support a flat cladding portion 5 against the center section of the girder 7. Proper ventilation is important to prevent condensation or any other build-up of moisture between the fire protection claddings and the structure. Drainage holes are also included, and in the embodiments shown, a drainage passage is shown in a mounting sleeve 16 which is attached to the cladding with a sleeve nut 17.

[0054] The bushing nut and the fastening nut 16 are shown in detail in Fig. 3. The fastening bushing 16 includes a fastening or drainage opening 15. The fastening bushing 16 can be covered on the inside with a fire-protective expanding layer which will seal the opening in the event of fire. The detail in Fig. 3 further shows an internally expanding epoxy layer 12, an externally expanding epoxy layer 13, and a perforated metal plate 14 within the epoxy layers. In FIG. 3 t1 represents a thickness of an inner expanding epoxy layer and t2 the thickness of the outer expanding epoxy layer.

[0055] Fig. 4 shows flat fire protection claddings 19 which are attached to corrugated claddings 18 with releasable mechanical fasteners 22. Nine claddings are shown, but it is clear that any number can be used to provide the necessary protection. The claddings are shown as rectangular elements, but the shape can be adapted to the underlying structure. However, it should be possible for a person to handle each garment so that it is easy to assemble and remove, so that the weight is usually limited to 25 kg.

[0056] Fig. 5 shows a detail in Fig. 4, showing both a cladding joint and how channels are formed between the fire protection cladding and the corrugated cladding 18. As explained earlier, it is important to maintain a distance between the fire protection claddings and the underlying structure. Figure 5 also shows an overlapping side joint 20 and a releasable mechanical fastener 22. The overlapping side joint 20 allows the mechanical fastener 22 to fasten two adjacent claddings. As will be seen from Fig. 5, it is difficult to maintain an equal distance between the cladding and the underlying structure. However, spacers can be used, and if a fire should occur, the heat in the structure will seek to spread to colder areas, thus cooling the areas closer to the cladding. Under such conditions, the outer expanding layer may be thicker than the inner expanding layer, so that a sufficiently thick, expanded layer is maintained.

[0057] The overlapping portions may be formed with grooves and recesses to facilitate assembly and to improve stability between adjacent claddings.

[0058] Fig. 6 shows how claddings, such as flat fire protection claddings 19, can be attached to a structure on top of hat-shaped spacer channels 33 with releasable mechanical fasteners 22. The detail in Fig. 6 shows how the claddings can be adapted to different shapes for different solutions without compromising fire protection properties. This is further shown in Figs. 8, which shows how flat fire protection claddings can be attached to the top of a spacer grid 32 made of cap-shaped channels to ensure proper spacing between the structure to be protected and the fire protection claddings, both to allow proper ventilation between the structure and claddings, and for to allow expansion of the epoxy layers against the structure in the event of a fire. The details in Figures 7 and 9 show typical cladding joints with releasable mechanical fasteners 22. Soluble mechanical fasteners in this context may be bolt and nut solutions, screws, pop nails, expanding plugs and so on.

[0059] Figure 10 shows how two curved protective coverings 3 can be assembled around a tubular object and be fastened to each other with locks 8. An edge portion 34 for distance distribution ensures a suitable distance between the curved fire protection cover 3 and the tubular object to be protected. [0060] Figure 11 shows two channel-shaped fire-protective coverings enclosing a girder 7, which are fastened to each other over a center position lock shown in detail in Figure 12.

[0061] Figure 12 also shows how the claddings overlap. The lock is typically attached to the claddings with pop nails.

[0062] Figure 13 shows another fastening method, in which two L-shaped fire-protective coverings are fastened to each other with fastening straps 35 around a channel section. A distance between the duct section and the L-shaped fire protection coverings is shown in detail in figure 14.

[0063] Figure 14 therefore shows an outer expanding layer 13, a perforated metal plate 14 and an inner expanding epoxy layer 12. A stepped edge is made along each of the L-shaped claddings to form a suitable joint. Figure 14 further shows that the perforated metal plate is bent with a Z-bend 27 along the edges to form the stepped edge 28.

[0064] Figure 15 shows a detail in cross section of a girder 7 which is covered with two L-shaped fire protection claddings having explosion reinforcements 6. The fire protection claddings are attached to the girder with fastening rods 25. An inner portion of the claddings is supported against a lower flange of the support, and the support includes a galvanic corrosion insulating material 24 between the support and the support to prevent galvanic corrosion. At the lower part of the protective coverings, the protective coverings are joined to locks 8. Heat-insulating fastener covers 23 protect the mechanical fasteners attached to the fastening rod 25, and also prevent the fastening rod from conducting heat towards the girder 7.

[0065] Figure 16 corresponds to a view which is right-angled on the cross-section of Figure 15, showing the girder 7, the claddings and the insulating fastener cover 23. In Figure 16 the insulating fastener cover 23 is shown as a hat-shaped channel. Each cover includes an internally projecting portion, to which the galvanically corrosion insulating material 24 is attached to prevent the covers from moving in a downward direction.

[0066] Figure 17 shows a detail of Figure 15, focusing on how the fastening rod 25 secures each cladding to the girder 7 with fastening nuts 26. Furthermore, Figure 17 shows how the insulating fastener cover 23 insulates the fastening nut 26 and the fastening rod 25 in the event of a fire. The insulating adhesive cover has a hat shape and includes inner and outer epoxy layers and a perforated metal plate similar to the other protective liners. The covers 23 ensure that the fastening rod and the fastening nuts maintain their integrity in the event of a fire, and also reduce the heat transfer through the fastening rod 25 to the girder 7. A distance g1 is shown between the cladding and the girder.

[0067] Figure 18 shows a specially made protective covering 36 which is specially adapted for a girder 7 which is partially immersed in a structure. Figure 18 also shows how fastening nuts 26 are protected with insulating fastener covers 23, and how a gap is maintained between the specially made protective cladding 36 and the girder 7. The insulating adhesive covers 23 can be attached to the specially made protective cover 36 with pop nails, or by any other means that allows the insulating adhesive covers to be removed in order to access attachment nuts 26, so as to facilitate removal of the protective cover which covers individual things that are attached.

[0068] Figure 20 shows a substantially L-shaped protective cladding, which is typically also shown in Figures 15 and 16, where the explosion reinforcement 6 also includes openings 29 to reduce the weight and to ensure proper ventilation and drainage. As previously mentioned, it is very important that no moisture builds up between the fire protection claddings and the underlying structure that the claddings are intended to protect.

[0069] Support elements 30 support the cladding, and are intended to bear against the lower flange of a girder. This is shown in Figure 15, which also shows a galvanic corrosion insulating material 24 which is between the girder and the supports 30.

Figures 21 and 22 show an alternative fastening element in cross-section and perspective view, respectively. A dedicated fastener 37 is particularly useful in an environment where explosion is a theme. The fastening element 37 can be attached to the girder 7 without any significant risk of sparks being created, which may typically be present during drilling and welding.

[0071] Figures 21 and 22 show L-shaped protective coverings which are fastened with fastening bolts to the fastening element 37.

[0072] Figure 23 is a detailed perspective view of the fastening element 37. The fastening element 37 may be clamped between the flanges of a girder with tension bolts 38 which allow the fastening element 37 to be clamped between the flanges. Cladding fastening bolts 39 are secured to the fastening element 37 for fastening fire-protective claddings.