GB2085514A - Fire resistant door - Google Patents

Abstract

A fire resistant door (1 or 2) comprises a core of incombustible mineral-based material (4) covered on both faces with a layer of facing material (6) and having its edges grooved. Wooden inserts (5) are received in the grooves with the outer faces of the inserts (5) flush with edges of the core (4). A composite lipping (7) is bonded around the edges and the lipping (7) includes a wooden layer (8) facing and bonded onto the outer face of the inserts (5) and the edges of the core (4), a layer of intumescent material (9), and an outer wooden layer (10), with the intumescent material (9) being completely encased and surrounded. This construction of fire resistant door is particularly suitable for receiving a vision panel (3), and in this case, an opening is cut in the core (4) and through the layers of facing material (6). This opening is lined with a strip of intumescent material (16) and wired glass (17) is located in position by steel pins (19) driven through the intumescent strip (16) and into the core (4). <IMAGE>

Description

SPECIFICATION Fire resistant door Different parts of a building are constructed as a number of separate compartments with a fire resisting barrier between each compartment.

Openings leading to and from the compartments are closed by fire resisting doors which firstly should prevent the transmission of combustion products such as smoke and noxious gases which may interfere with an escape route in an adjacent compartment and secondly should act as a barrier to prevent the fire spreading from one compartment into the next. To have a one hour rating as a fire resistant door a door must retain its integrity and its stability for a period of one hour when tested in accordance with the procedure set out in British Standard BS 476: Part 8:1972.

Thus, under this test a fire resistant door must be resistant to collapse, and resistant to penetration by flame or hot gases or to spontaneous ignition of its side not exposed to the fire for a period of one hour. This invention is concerned with a door which satisfies these requirements.

The first thing that has to be considered is the basic material from which the door is manufactured. In general, non-combustible material is readily available of suitable size and thickness for use as a fire door but, in general, such non-combustible material is very friable and it is difficult to make strong fixings in such material. Further, any exposed edges of the material tend to spall and break away and so are easily damaged. This problem is usually overcome by providing a framework around the outside of the door which provides the mechanical strength of the door and provides the fixing points for hinges, latches and other door furniture but, in this case, the integrity of the door is only as good as its framework no matter how incombustible the central portion of the door.

Another area of weakness is the gap surrounding the edges of the door. To enable the door to open and close readily there must be some clearance between the door and its frame and it is through these gaps that smoke and other combustion products can escape. Hot gases from a fire can also escape through these gaps and spread the fire. One way of overcoming this is to provide intumescent material around the outside of the door which, in the presence of fire expands to fill any gaps around the edges of the door. At present, this intumescent material may be applied in a variety of ways. One of the most popular is to provide grooves in the exposed edges of the door and fill these grooves with an intumescent paste.

This is inconvenient because the grooves have to be cut and then filled with intumescent paste after the doors have been fitted and it is not particularly satisfactory because it is common to have to ease a door after its fitting and this is very likely to remove all the intumescent material. To overcome this, the intumescent material is frequently applied as a strip to the inside of the door frame and it has also been proposed to encase the intumescent material in a sheath of plastics material and fix this to the frame of the door, or encase it in timber in the frame.The intumescent material must be protected from the atmosphere and be protected from mechanical damage since it is relatively soft and friable and it does not look particularly pleasing so that taking all these factors into account it has proved difficult to provide a satisfactory mounting for the intumescent material to fill the gaps between the door and its frame in the event of a fire. One proposed construction has been to fix a strip of intumescent material to the edge of the door and then apply a lipping outside the intumescent material. There are practical difficulties in doing this because it is difficult to get a satisfactory bond between the intumescent strip and, both the lipping and the door.Conventionally, lipping is fixed to a door using an adhesive which is cured by RF radiation and the presence of the intumescent material prevents this technique from being used since the RF radiation heats the intumescent material to such an extent that it begins to swell and expand.

It is also necessary to take some further action to cover the edges of the intumescent material, for example by covering the entire outer surface of the door with a further veneer skin, the edge of which is then unprotected because it is laid over the edges of the lipping.

A further problem in the construction of fire resistant doors is the provision of vision panels through them. It is desirable to include vision panels in fire doors so that, in normal use, the user of the door can make sure that nobody is standing immediately behind the door before opening it and this is particularly important when the door is capable of swinging in both directions. Perhaps more importantly, a vision panel enables the presence of smoke or flame on the opposite side of a fire door to be detected. In the event of a fire the provision of a vision panel also enables a person fighting the fire to inspect the state of the fire without the necessity of opening the door and, by smashing the vision panel, the remainder of the door provides something of a shield through which the fire can be tackled.However, the presence of a vision panel which is usually a glazed panel means that a large quantity of heat is radiated through the panel and also, since glass is a relatively good conductor compared to the material from which the door is made, a large quantity of heat is also conducted through the glazed panel. The radiant heat and the heat conducted through the panel leads to the beads holding the panel in place on the side of the panel remote from the fire being readily ignited and this frequently leads to premature failure of the door. Often a conventional fire resistant door is made of material which is gradually consumed by the fire, in this case the consummation of the side of the fire door by the fire and the beads leads to premature failure of the door since the glazing panel is no longer supported and simply falls.Also, it is difficult to seal completely the gaps between the glazing panel and the remainder of the door with the result that this forms a further path through which hot gases and other combustion products can escape. At present, there is only one type of glazing mount that is satisfactory for fire doors with a one hour rating and that uses an intumescent coated non-combustible glazing channel sold under the tradename of Trada Marinite. This channel is aesthetically unappealing and it is frequently covered by a wooden or aluminium cover which adds a further item to the cost of the door.

According to this invention a fire resistant door comprises a core of incombustible mineral-based material covered on both faces with a layer of facing material and havings its edges grooved, wooden inserts received in the grooves with their outer faces flush with the edges of the core and a composite lipping bonded around the edges, the lipping including a wooden layer facing and bonded onto the outer face of the inserts and the edges of the core, a layer of intumescent material, and an outer wooden layer, with the intumescent material being completely encased and surrounded.

Preferably the composite lipping includes a strip of intumescent material which is completely encased and surrounded by wood. This may be achieved by having the lipping formed by a Ushaped rectangular wooden channel with a strip of intumescent material located in the base of the channel and with a fillet of wood glued into or on top of the intumescent material to provide a lipping which is rectangular in cross-section. Other ways of achieving this are to provide two wooden strips each having an L-shaped cross-section and fixing these together face-to-face to encase a strip of intumescent material between them, or two grooved strips bonded together with grooved edges facing one another to encase a strip of intumescent material between them. This composite lipping is then fixed to the door and it appears as a conventional rectangular section wooden lipping.

This composite lipping can be treated in exactly the same way as a conventional lipping and made up in advance and even be sold separately to uprate existing doors. The lipping may be fixed to the edges of the door using RF radiation because the intumescent strip is away from the joint between the edge of the core and the lipping and so as it is away from the focus of the radiation it is not strongly heated, and so not heated sufficient to activate it to cause it to expand and foam.

Preferably the thickness of wood between the intumescent strip and the outside edge of the door is sufficient to allow it to be fitted during installation and eased in subsequent operation without exposing the intumescent strip. Typically, there is a thickness of about 5 mm. When the door forms a single leaf door such as composite lipping is placed on all the edges of the door but, when the door forms one leaf of a double leaf fire door, then such a lipping is preferably only used on the three outer edges of each door with a different arrangement used on the meeting edges of the doors.

In the case of a double leaf door, the meeting edges of the doors preferably include a simple composite lipping formed by a layer of wood, a layer of intumescent material and a second layer of wood laminated together. This laminate is then fixed to the meeting edges of the doors by Lshaped aluminium sections which serve to protect the meeting edges of the door and provide a housing for a cold smoke seal, for example a brush-type smoke seal. The layers of wood on each side of the intumescent strip are usually thin, typically 2 mm thick and so it is simple to bond the laminate in a heated press. The laminate can be removed by removing the L-section aluminium strips if it ever becomes necessary to ease or fit the meeting edges of the doors.

The incombustible mineral-based core is preferably made from compressed vermiculite because this material has the advantage that it is easy to work with conventional woodworking tools but any incombustible material that is capable of being fashioned into the required shapes may be used.

The particular construction of fire resistant doors in accordance with this invention is particularly suitable for receiving a vision panel and, in this case, an opening is cut in the core and through the layers of facing material. This opening is lined with a strip of intumescent material and wired glass is then located in position by steel pins driven through the intumescent strip and into the core. In the event of a fire the intumescent strip swells to seal any gaps between the edges of the glass panel and the inside edge of the core and also tends to swell up on each side of the glass to form a generally U-shaped channel which also helps to retain the glass.Because the core of the door is formed from a material which is noncombustible and so is not consumed or eroded by fire the steel pins continue to retain the glass in position in the event of fire even if the pins become red hot. In a door of conventional construction with a timber core, steel fixings merely tend to conduct heat into the wooden core and lead to premature failure and erosion of the core. Preferably the glass is surrounded on both sides by beading coated or impregnated with intumescent material so that it is protected from heat transmitted by radiation through the glass and it is also preferred that asbestos tape is placed between the beading and the glass to help insulate the beading from the glass and so prevent its combustion by heat conduction through the glass. The beading is preferably fixed by steel screws extending through the beading and into the core. These steel screws also serve to retain the glass panel even after the beadings on the exposed side of the door have been completely consumed by fire.

The wooden inserts provide a good fixing for the hinges, the latch and other furniture such as door closers and provide a good surface to which the lipping can be bonded. However, since the inserts are received into the grooves with their outer faces flush with the edges of the core, the inserts are protected on both sides by the core material and we have found that the provision of these wooden inserts does not materially reduce the integrity of the core material in the event of it being exposed to fire. Thus, with the construction of fire resistant doors in accordance with this invention, substantially the entire area of the opening is sealed by the non-combustible material forming the core and this presents an added degree of security.Mostly, the lipping is covered on one face by the stop on the door frame but, in any event, due to its composite nature it forms an effective barrier for the passage of fire.

The construction of a pair of fire resistant doors in accordance with this invention will now be described with reference to the accompanying drawings; in which:~ Figure 1 is an elevation of the doors; Figure 2 is a part horizontal section through the doors to an enlarged scale; and, Figure 3 is a vertical section through the glazed door.

The dors 1 and 2 are both the same size and each 1984 mm by 760 mm by 46 mm. The door 1 includes a vision panel 3 with an exposed glass size of 780 mm by 180 mm and an overall aperture size of 818 mm by 218 mm. The basic construction of each door is identical and comprises a core 4 of non-combustible compressed vermiculite sheet 40 mm thick sold under the tradename of Thermax Type SN 450 Non-Combustible Board. Each edge of the board is grooved to receive a tongued hardwood frame 5 having overall dimensions of 56 mm by 25 mm with a 13 mm square tongue. The frame 5 is bonded into the core 4 using a resorcinol based adhesive. A deeper frame portion may be provided as a pad for the latch and to provide a fixing for the handles. A facing 6 of 3.2 mm thick hardboard or plywood is bonded onto the outside faces of the core 4.The top, bottom and hinge side of each door is edged with a composite lipping 7 formed by a U-shaped rectangular channel shaped piece of hardwood 8 with a strip of intumescent material located in the base of the channel. A fillet 10 of hardwood is then placed on top of the intumescent strip 9 and glued in position in the channel of the channel-shaped portion 8, to completely encase the intumescent strip 9. There is a 5 mm thickness of hardwood on the outer sides of the intumescent strip 9. The intumescent strip 9 is preferably formed by wire mesh reinforced hydrated sodium silicate coated with an epoxy resin which is known by the tradename of Palusol Fireboard 210.

On the meeting edge of the two doors a laminated lipping consisting of a 1.8 mm thick strip of intumescent material 10, preferably Palusol Fireboard 210 is bonded onto a layer of 42SWG aluminium 11 and sandwiched between two strips of hardwood veneer 12 and 13 each approximately 2 mm thick. On the edge of the door 1 the outer wood veneer 13 is only 22 mm wide and then this laminated lipping is held in place by two L-shaped sections 14 of aluminium angle each of which has overall sizes of 25 mm by 12 mm and is approximately 1.5 mm thick. The aluminium angle 14 is screwed at 270 mm centres to the faces of the door. The lipping on the meeting edge of door 2 is 26 mm wide and again formed as a laminate of wood veneer, aluminium, and intumescent strip as with door 1.A brushtype smoke seal 15 is located along each edge of the door 2 and preferably these are of a type sold under the tradename of Schlegal Sharkseal. The vision panel 3 fitted in the door 1 is formed by lining the aperture with a 32 mm wide 1.8 mm thick strip of Palusol 210 intumescent material 16 and then mounting a panel of 6 mm Georgian Wired Polished plate glass 17 on the intumescent strip 16. Asbestos tape 18 25 mm wide by 3 mm thick is fitted to each side of the glass to form a border around the perimeter of the glass approximately 20 mm wide and extending to the edge of the intumescent strip 1 6. The glass 1 7, the asbestos tape 18 and intumescent strip 16 are held in place by steel glazing sprigs 19 driven directly into the core 4 of compressed vermiculite.

1-9 mm square glazing beads 20 with their internal arris rebated out are then screwed in position using 2-" No 7 countersunk head steel wood screws 21 at 175 mm centres and the bead is coated with an intumescent paint or varnish, for example that sold under the tradename Albiguard.

Typically, the doors 1 and 2 are hung in a softwood frame 22 having overall dimensions of 92 mm by 57 mm and a rebate of 48 mm by 12 mm and are hung using 13 pairs of steel butt hinges 23 on each door. Typically, there is a 6 mm gap between the meeting edges of the doors 1 and 2 and a 2-3 mm gap between the edges of the doors 1 and 2 at their hinge sides of the frame and at the top and bottom of the door.

A door in accordance with this invention was tested in accordance with the provisions laid down in British standard BS476 :Part 8:1972 and under this test doors maintained their stability and integrity for some 69 minutes before failure.

During the course of the test, after about 14 minutes the intumescent strips 9, 12 and 16 had all expanded to such an extent that substantially no gaps remained around the edges of the door so that substantially no leakage of combustion products took place around the doors after this time had elapsed. The glass panel 17, although cracked, remained in place after the test, it being retained by the asbestos tape 18 and the sprigs 19 and screws 21 in spite of the bead 20 on the exposed side of the door having been completely consumed by fire. The doors failed by the escape of hot gas from around the top edge of the glass 17. It is expected that a door not including a vision panel would have a considerably longer stability and integrity.

Claims (13)

1. A fire resistant door comprising a core of incombustible mineral-based material covered on both faces with a layer of facing material and having its edges grooved, wooden inserts received in the grooves with their outer faces flush with the edges of the core, and a composite lipping bonded around the edges, the lipping including a wooden layer facing and bonded onto the outer face of the inserts and the edges of the core, a layer of intumescent material, and an outer wooden layer, with the intumescent material being completely encased and surrounded.

2. A fire resistant door according to claim 1, in which the composite lipping on at least three edges of the door includes a strip of intumescent material which is completely encased and surrounded by wood.

3. A fire resistant door according to claim 2, in which the lipping is formed by a U-shaped rectangular wooden channel with a strip of intumescent material located in the base of the channel and with a fillet of wood glued into the channel or on top of the intumescent material and the channel to provide a lipping which is rectangular in cross-section.

4. A fire resistant door according to claim 2, in which the lipping is formed by two wooden strips each having an L-shaped cross-section fixed together face-to-face to encase the strip of intumescent material between them.

5. A fire resistant door according to claim 2, in which the lipping is formed by two grooved wooden strips bonded together with their grooved edges facing one another, and with a strip of intumescent material encased between them.

6. A fire resistant door according to any one of the preceding claims, in which the core is made of a compressed vermiculite.

7. A fire resistant door according to any one of the preceding claims, including a vision panel, and in which an opening is cut in the compressed vermiculite core and through the layers of facing material, the opening is lined with a strip of intumescent material, and wired glass is then located in the opening and held in position by steel pins driven through the intumescent strip and into the compressed vermiculite core.

8. A fire resistant door according to claim 7, in which the wired glass is surrounded on both sides by beading coated or impregnated with intumescent material so that it is protected from heat transmitted by radiation through the glass and in which asbestos tape is placed between the beading and the glass to help to insulate the beading from the glass and so prevent its combustion by heat conduction through the glass.

9. A fire resistant door according to claim 8 in which the beading is fixed by steel screws extending through the beading and into the core.

1 0. A fire resistant door according to claim 1, constructed substantially as described with reference to the accompanying drawings.

11. A pair of fire resistant doors each of which is constructed in accordance with any one of the preceding claims, and in which the meeting edges of the doors preferably include a simple composite lipping formed by a layer of wood, a layer of intumescent material and a second layer of wood laminated together.

12. A pair of fire resistant doors according to claim 11, in which the laminate on the meeting edges of the doors is fixed to the meeting edges of the doors by L-shaped aluminium sections which serve to protect the meeting edges of the door and provide a housing for a cold smoke seal, such as a brush-type smoke seal.

13. A pair of fire resistant doors according to claim 11, constructed substantially as described with reference to the accompanying drawings.