This invention relates to passive fire protection covers or enclosures particularly but not exclusively for use in the oil and gas industry. In the event of fire it is important to be able to shut off the flow of oil or gas for example from a well and the object of the passive protection is to minimise heat rise in a control valve and its actuator to enable this to be done. Erosive flames resulting for example from ruptured pipe work in which oil or gas is flowing at pressure, are particularly difficult to protect against with conventional materials.

However as will be appreciated the invention may find uses in other applications and other industries.

According to the invention, a passive fire protection sheet material comprises at least one layer of insulant and at least one layer which includes a cross- linked rubber compound containing a frit based composition.

The rubber material preferably has fire resistant properties. Suitable frit is disclosed for example in U.K. Patents numbered 2188643, 2220208, 2221318, 2232986 and 2234754. Under fire conditions the rubber burns to produce a char which contains the frit, and the frit fuses to form a protective layer. The rubber may be on the outside of an enclosure, and if so provides erosion protection to the insulant located inside it, enabling the latter to contribute to the fire protection without being physically destroyed. However the rubber may be on the inside and/or there may be alternate layers of both.

The insulant may be ceramic fibres which by their nature are heat resistant and trap air. But other materials are possible for example clay particles or beads trapped in a blanket, quilt or duvet, or calcium silicate as another example.

One presently preferred embodiment of the invention is now more particularly described with reference to the

accompanying drawings in which :-

Figure 1 is a diagrammatic sectional perspective view of a passive fire protection in place;

Figure 2 is an enlarged and more detailed sectional view of one of the layers of ceramic fibres;

Figure 3 is a view similar to Figure 2 but showing an alternative; and

Figure 4 is a fragmentary sectional view of another layer of the material used in Figure 1.

Turning now to Figure 1, the reference 10 indicates a steel substrate representing an article which is to be fire protected. It will be understood that this may be a valve or any other article of any shape, often quite complex shape: the drawing shows a simple parallelopiped shape. The reference 12 indicates a first layer of the ceramic fibre material as more particularly described hereunder. This layer 12 is held in position for example by steel straps 14. A second layer 16 is or may be the same as layer 12 and is likewise held in position by further straps 18. An outer layer 20 of the rubber/frit material is also held in place by steel straps 22 and there may be a further protective enclosure not shown.

Turning now to Figure 2, the ceramic fibre material forming the layers 12, 16 may be loosely or otherwise felted into a sheet material 30 and enclosed in a duvet 32 of a cloth, which may be a felted or woven textile material, or a cloth made by impregnating glass fibre sheet material with a suitable resin mix. The object is to disperse the fibres uniformly through the material 12, 16, and maintain it in position. The ceramic fibre may be held in position within the duvet by the use of ceramic or metallic fixing pins 34. This may help to prevent the ceramic fibre from creeping away from the duvet edges.

However, it is to be understood that Figure 2 is particularly diagrammatic and does not necessarily represent the thickness of the sheet as it is in

practice. A sheet may be used for example in the order of 12.5, 25, 38 or 50mm thickness and any combination of layers of this or these thicknesses. The rubber/frit layer or layers may be of the order of 5mm thick.

Figure 3 shows an alternative construction for the layer(s) 12, 16, in which the fibres are a long-fibre ceramic wool felted into a sheet which may be folded into a sinuous shape 30, and enclosed in a jacket 32 of silicon coated glass cloth. The glass cloth may be felted or woven, and may be impregnated with a suitable resin mix.

Whatever construction is used for the ceramic fibres, the object is to trap massive volumes of air.

More particularly, the layer 20, see Fig. 4, is made of a fire resistant PVC/rubber compound 40 with the dispersed ceramic frit particles therein. This material may be the one sold by Brunner Mond & Company under the trade mark CEEPREE. The rubber could be neoprene, chloroprene, EPDM or a copolymer of a polyolefin including ethylene. Preferred values are 40-60% rubber, 20-30% Ceepree frit, and balance filler which may be ceramic or fibre, e.g. Mullite, or AI2O3.

This rubber/frit layer is enclosed between a backing cloth 42 and a glass cloth made of resin impregnated glass fibres 44, with an abrasion resistant coating 46 on the exterior.

A preferred composition is 60% rubber, 20% Ceepree and 20% fibre filler.

The fire protection arrangement according to Figure 1 has been tested. For these purposes a 4mm thick layer of the rubber/frit was employed. 75mm thick layers of the ceramic fibres having a weight of 128 kg/m , encased in glass cloth (h) of an average weight of 576 g/m~ were used. The construction was as shown in Figs 1 and 3. The test was on a dummy valve and actuator system at the British Gas testing facility at Spadeadam, Cumbria,

following the standard procedure used in the oil industry for such purposes. In this test propane gas is fed at the rate of 3 kg per second through a 22mm steerable nozzle to produce a long fierce erosive flame. The jacketed dummy valve and actuator are located some 10 meters from the nozzle in the core of the flame where the temperature is of the order of 1100-1200 degrees C.

After some 15 minutes the fuel flow rate is reduced to 2 kg per second for the remainder of the test. Few passive fire protection systems last that long before they are utterly destroyed.

The system survived the test for 102 minutes, when the test was terminated. The system maintained its integrity for the duration of the test and afforded a significant degree of protection to the dummy actuator.

The degree of protection can be varied by increasing or decreasing the thickness of ceramic fibre.