GB1571394A

GB1571394A - Heat shields

Info

Publication number: GB1571394A
Application number: GB2881376A
Authority: GB
Original assignee: LOCKER WIRE PRODUCTS Ltd
Current assignee: LOCKER WIRE PRODUCTS Ltd
Priority date: 1977-07-05
Filing date: 1977-07-05
Publication date: 1980-07-16

Description

(54) HEAT SHIELDS (71) We, LOCKER WIRE PRODUCTS LIMITED, formerly known as LOCKER WIRE WEAVERS LIMITED, a British Company, of P.O. Box 161, Church Street, Warrington WA1 2SU, Cheshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to heat shields, particularly for use in shielding offshore oil rigs and allied installations from intensive heat and flames produced for example by the burning of waste hydrocarbons.

According to the present invention there is provided a heat shield suitable for use in shielding oil rigs and allied installations from burning waste hydrocarbons, the sheild having at least one sheet of fireresistant material which is of wire mesh construction and is mounted on a frame whose members include a plurality of skeletal side members.

In one embodiment, one or more of the frame members comprises four such elongate and substantially parallel support members arranged in spaced apart pairs.

Conveniently the support members of one or each pair are spaced apart along at least a portion of their length to enable one or more sheets of fire-resistant material to be easily secured to the frame, for example by bolts which pass through the gap or gaps between the spaced apart portions.

The support members may be interconnected by tie bars conveniently of circular cross-section and where a side member includes two pairs of support members the tie bars are preferably secured between the support members of each pair.

Advantageously each support member is a rod of substantially circular cross-section.

Where necessary, one or more additional bracing struts preferably similar in construction to the side members are included in the frame. The bracing members interconnect side members to provide additional strengthening.

The present invention is further described hereinafter, by way of example, with reference to the drawings accompanying the Provisional Specification in which: Fig. 1 is a perspective view, partially broken away, of a preferred embodiment of a heat shield according to the present invention; Fig. 2 is a section through one side member of the heat shield of Fig. 1 along the line II-II; Fig. 3 is a detail of one corner of the heat shield frame; Fig. 4 is a section through a bracing member of the heat shield of Fig. 1 along the line III-III; and Fig. 5 is an exploded perspective of one form of mounting for a sheet of fire-resistant material.

Fig. 1 illustrates one form of heat shield 10 which is suitable for use on off-shore oil rigs to shield the rigs from the intense heat and flames produced by the burning of waste hydrocarbons.

The heat shield 10 basically comprises three primary sheets 11 and three secondary sheets 12 of fire-resistant wire mesh material mounted respectively on each side of a substantially rectangular frame 14. Only five sheets are shown, however, with two primary sheets 11 partially broken away to clearly show the mode of construction of the frame 14.

The frame 14 includes four side members 16 each in the form of a ladder-like element.

As best seen in Fig. 2 each side member 16 consists of four elongate support members in the form of rods 18 arranged in upper and lower pairs in a substantially parallel and spaced-apart relationship, each rod pair comprising an inner and outer rod. Both pairs of rods 18 are rigidly joined together by tie bars 20 whose respective ends 22 are secured between the rods 18 of each pair.

Fig. 3 clearly illustrates the method of jointing two adjacent side members 16 of the rectangular frame 14. The inner rods of one of the adjacent side members 16 are cut away sufficiently to allow the rods 18 of the second side member 16 to butt against the outer rods 18 of the one side member 16.

Two tie rods 20 interconnect the upper pairs of side members 16 with the lower pairs to strengthen the corner joint and additional rigidity is provided by two corner tie rods 24 which interconnect respectively the upper and lower inner rods 18 diagonally across the corner.

The illustrated frame 14 also includes two bracing struts 26 which interconnect the opposing longer side members 16 of the rectangular frame 14. Such bracing struts are generally required only where the frame area is greater than 24 sq. ft., for example, in a 6' x 4' frame. The principle of construction of each bracing strut 26 is identical to that of the side members 16 and, as is best seen from Fig. 4, where two adjacent sheets 12 butt along the bracing strut 26 the latter basically consists of two side members rigidly secured side by side for reasons explained below. Where this is not the case the bracing member may be formed by a single side member 16. The bracing struts 26 are secured to the opposing side members 16 at locations of high strength, in this example adjacent tie rods 20 of the side members 16.

Corner ties 24 are conveniently provided at the junction of the bracing struts 26 and the side members 16 for greater rigidity.

The frame 14 is generally made of stainless steel or mild steel rods; in the latter case the frame is galvanised or painted with heat resistant paint. The rods are conveniently it" diameter circular cross-section but may alternatively be of any suitable crosssectional shape, for example square, oval or tubular section. All joints in the framework are preferably welded joints.

The fire-resistant sheets 11 and 12 are generally stainless steel or galvanised radiant wire mesh and are bolted to the frame 14 in the manner illustrated in Fig. 5.

Each bolt 28 is of slightly smaller diameter than the spacing between adjacent rods 18 (the diameter of the tie rods 20 may be chosen to suit a particular sized bolt) thus facilitating the bolting of the wire mesh sheets to the frame 14 by obviating the need to drill bolt holes in the frame. Additional securing washes 30 and 32 and a spring washer 34 are also provided. This method of securing wire metal sheets to the frame 14 is to be preferred since it enables easy replacement of damaged wire mesh sheets.

In use, the primary wire mesh sheets 11 will face the heat source and are chosen dependent upon the temperatures which they have to resist, for example, for temperatures of 600"C. to 700"C., 8 mesh 16 gauge standard is adequate. The secondary wire mesh sheets are basically provided to prevent accidental contact with the primary mesh sheets and may be of a low grade mesh e.g. 3 mesh 14 gauge standard. The primary and secondary wire mesh sheets are radiant mesh.

The air gap between the primary and secondary wire mesh sheets to a large extent determines the temperature drop across the heat shield. In the described embodiment the air gap is approximately 6 inches resulting in a temperature drop of from approximately 600"C. to 70do. across the shield.

As an alternative to radiant mesh the primary, and if required the secondary wire mesh sheets may be of flame arresting mesh.

However, this is a much lighter mesh than radiant mesh and is disadvantageous in that it neither reflects nor absorbs as much heat as radiant mesh. Preferably, the primary sheets consist of respective layers of flame arresting and radiating wire mesh sheets to combine the advantages of both forms of mesh.

A number of the illustrated heat shields are conveniently bolted to the drilling rig with bolts passing between inner and outer rods 18 of the side members 16, to shield large areas of the rig. Alternatively, the shields may be slotted into channels formed by paralled I- or U-section steel beams secured to the rig. This method of mounting facilitates the removal of defective shields for repair but requires the addition of bearing plates to abutting ends of the shields. A bearing plate is shown dotted in Fig. 2 and prevents an outer rod 18 of an abutting shield settling into the space between the outer rods of Fig. 2 since this can result in a considerable loss of length where a large number of shields are aligned in one I-section channel.

Heat shields according to the present invention exhibit a considerable advantage over equivalent previously known heat shields which are generally made of heavy U-section steel channel. The open construction of the frame of a heat shield of the present invention results in a much lighter shield and improved efficiency; the frame itself blocks off a much smaller surface area of the primary wire mesh sheets allowing greater dissipation of heat by the mesh and reducing heat conduction through the frame from the primary to the secondary mesh sheets. For example, an average sized 12' x 6' shield of the present invention would weigh approximately 150 kilos, whereas an equivalent prior art shield would weigh approximately 310 kilos, the mesh sheets weighing the same, 54 kilos, in both cases.

In addition, the frame of the former heat shield would have an open area facing the primary wire mesh sheets of approximately 72 sq. ft. whereas the frame of the latter shield would have an open area of approximately 60 sq. ft., the greater area of contact of the frame with the primary mesh sheets reducing the efficiency of the latter and increasing heat conduction through the frame.

Furthermore, the open construction of the frame of a heat shield according to the present invention obviates the need for additional lifting plates to be secured to the frame since the tie rods of the frame can serve this purpose; lifting plates provide a securement for the lifting tackle of a crane or other lifting gear.

WHAT WE CLAIM IS: 1. A heat shield suitable for use in shielding oil-rigs and allied installations from burning waste hydrocarbons, the shield having at least one sheet of fireresistant material which is of wire mesh construction and is mounted on a frame whose members include a plurality of skeletal side members.

2. A heat shield as claimed in claim 1, wherein said members include at least one bracing strut interconnecting two or more of said side members for strengthening the frame.

3. A heat shield as claimed in claim 1 or 2, wherein at least one of the frame members comprises a plurality of elongate, substantially parallel spaced apart support members.

4. A heat shield as claimed in claim 1, 2 or 3, wherein at least one of the frame members comprises four elongate and substantially parallel support members arranged in spaced apart pairs.

5. A heat shield as claimed in claim 4 wherein the support member of one or each pair are spaced apart along at least a portion of their length whereby to receive means for securing said at least one sheet thereto.

6. A heat shield as claimed in claim 5 wherein the or each sheet is secured to the frame by bolts passing between said spaced apart support members.

7. A heat shield as claimed in any of claims 3 to 6, wherein the spaced apart support members are interconnected by tie bars.

8. A heat shield as claimed in claim 7 when appendant to claim 4 or 5 wherein the tie bars are secured between the support members of each pair thereof.

9. A heat shield as claimed in claim 7 or 8, wherein the tie bars are rods of substantially circular cross-section.

10. A heat shield as claimed in any of claims 3 to 9, wherein the support members are rods of substantially circular crosssection.

11. A heat shield as claimed in claim 9 or 10, wherein the rod cross-section is substantially -21-inch in diameter.

12. A heat shield as claimed in any of claims 1 to 11, further comprising at least one secondary sheet of fire-resistant wire mesh material mounted on the frame opposing said at least one sheet.

13. A heat shield as claimed in any of claims 1 to 12, wherein one or more sheets of fire-resistant material comprises radiant wire mesh.

14. A heat shield as claimed in any of claims 1 to 12, wherein one or more sheets of fire-resistant material comprises flame arresting wire mesh.

15. A heat shield as claimed in any of claims 1 to 12, wherein one or more sheets of fire-resistant material comprises layers of flame-arresting and radiant wire mesh.

16. A heat shield suitable for use in shielding oil rigs and allied installations from burning hydrocarbons, constructed substantially as hereinbefore described with reference to the drawings accompanying the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. equivalent prior art shield would weigh approximately 310 kilos, the mesh sheets weighing the same, 54 kilos, in both cases. In addition, the frame of the former heat shield would have an open area facing the primary wire mesh sheets of approximately 72 sq. ft. whereas the frame of the latter shield would have an open area of approximately 60 sq. ft., the greater area of contact of the frame with the primary mesh sheets reducing the efficiency of the latter and increasing heat conduction through the frame. Furthermore, the open construction of the frame of a heat shield according to the present invention obviates the need for additional lifting plates to be secured to the frame since the tie rods of the frame can serve this purpose; lifting plates provide a securement for the lifting tackle of a crane or other lifting gear. WHAT WE CLAIM IS:

1. A heat shield suitable for use in shielding oil-rigs and allied installations from burning waste hydrocarbons, the shield having at least one sheet of fireresistant material which is of wire mesh construction and is mounted on a frame whose members include a plurality of skeletal side members.