Nozzle for water-based fire suppression system

Abstract

A seal is provided between a plunger (209) and a fluid conduit (205) of a nozzle (101) for a 5 water mist fire suppression system. The fluid conduit (205) is provided with an interior landing (301) ex

Description

Field of the Invention The present invention relates to a nozzle, and more particularly to a nozzle for a water mist fire suppression system. Background of the Invention Various types of fire suppression system are known, including water-based systems, such as sprinkler systems comprising sprinkler heads and water mist systems comprising water mist nozzles, that respond to a rise in temperature to discharge water to control, suppress or extinguish a fire. A typical automatic sprinkler head / water mist nozzle comprises a body that defines a fluid port and at least one discharge orifice, the fluid port being normally closed by a plug (also known as a pip cap or a plunger) that is held in in a flow-restraining position, to prevent water flowing from through the fluid port (into the body and through the at least one discharge orifice), by a heat-sensitive element, such as a frangible bulb or a fusible element, which is designed to rupture when exposed to heat exceeding a temperature threshold. When the heat-sensitive element ruptures, the plug is released from the flow-restraining position to open the fluid port and allow water to flow from pipework leading to the fluid port to the body for issue through the one or more discharge orifices. Thus, the rupturing of the heatsensitive element triggers the discharge of water from the head / nozzle. A typical sprinkler / water mist fires suppression system comprises a plurality of sprinkler heads / water mist nozzles that are designed to be activated individually so that only those in the vicinity of a fire will release spray / mist. There are different configurations of water-based fire suppression system. In a 'wet pipe' system, a supply conduit to the head / nozzle is always charged with water so that water is available for discharge immediately upon the head / nozzle being activated. In a 'dry pipe' system, the supply conduit is filled with pressurised air with a control valve holding water back downstream; the pressurised air is released when the head / nozzle is activated, and the control valve responds to the resultant drop in air pressure in the supply conduit by opening to allow the water to flow to the head / nozzle. A 'dry pipe' system may be deployed in scenarios in which there is a risk of water in a section of the supply conduit leading to the head / nozzle freezing but is associated with a delay between the head / nozzle being activated and water being issued from that head / nozzle that is not experienced with a 'wet pipe' system. In an 'alternate pipe' system, the pipe leading to the head / nozzle is configurable between 'wet pipe' and 'dry pipe' configurations, advantageously enabling a 'wet pipe' arrangement to be used during warmer months and a 'dry pipe' arrangement to be used during colder months. A water mist system utilises less water than, and creates a smaller droplet size, than a sprinkler system. While both sprinkler systems and water mist systems work in more than one way simultaneously to suppress a fire, and both provide the aspects of dampening, which functions to limit spread of fire, and reducing temperature, which functions to prevent re-ignition, only water mist systems provide the additional aspect of the water turning into steam on meeting the flame, which functions to deprive the fire of oxygen. The operating pressure of a water mist fire suppression system may vary between applications, and a higher water pressure may be used to create a finer mist. A problem identified with water mist fire suppression systems having a 'wet pipe' configuration relates to maintaining a proper seal within the water mist nozzle between the pressurised water in the supply conduit and the plug. It is to be appreciated that should the seal fail, water will leak from the nozzle and the undesirable discharge of water can cause damage and disruption. While a mechanical gasket in the form of an O-ring may be utilised in a way that provides a sufficient seal initially, O-rings are prone to deterioration over time and the progress of degradation can be difficult to assess. The current British Standard BS 8663-1:2019 Fixed fire protection systems. Components for watermist systems. Specification and test methods for watermist nozzles, which specifies requirements and gives test methods for the construction and performance of open and automatic watermist nozzles for use in watermist systems conforming to BS 8458 (residential and domestic watermist systems) or BS 8489-1 (industrial and commercial watermist systems), does not allow for such sealing components and requires a direct mechanical seal to be used. Some of the testing prescribed in the British Standard involves the application of heat and / or immersion in a liquid, which can cause a sealing component to deform or disintegrate with the outcome that the test is ineffective. It is an object of the present invention to provide an improved seal within a water mist nozzle for a water mist system having a 'wet pipe' configuration. Summary of the Invention According to a first aspect there is provided a nozzle for a water mist fire suppression system, the nozzle comprising: a body defining a fluid conduit, extending between a fluid inlet for connection to a supply of water and a fluid outlet, and at least one discharge orifice, and a flow control arrangement for controlling flow through the fluid outlet, the flow control arrangement comprising: a plunger movable relative to the fluid conduit between a flowpreventing position, to seal the fluid conduit, and a flow-allowing position, to unseal the fluid conduit, and a heat-sensitive element configured to rupture in response to exposure to a temperature exceeding an activation temperature threshold, the flow control arrangement configured to: maintain the plunger in the flow-prevent!ng position while the heat-sensitive element remains unruptured, and allow the plunger to move to the flow-allowing position upon rupture of the heat-sensitive element; the fluid conduit having a longitudinal axis and comprising a transversely extending interior landing, the interior landing defining a passageway extending therethrough between an upstream side and a downstream side of the interior landing, and the plunger comprising a plugging end having a protuberance, the plugging end of the plunger profiled to mate with the downstream side of the interior landing, with the protuberance projecting through the passageway and beyond the upstream side of the interior landing, for providing a seal between the plunger and the fluid conduit when the plunger is in the flow-preventing position. The nozzle advantageously enables a seal between the plunger and the fluid conduit to be provided that relies only on a surface of the plunger mating with a surface of the fluid conduit. In an example, the heat-sensitive element has a first end to interface with the plunger and a second end to interface with the body of the nozzle. In an example, the flow control arrangement comprises a biasing element for resiliently biasing the plunger towards the flow-allowing position. In an example, the biasing element is a compression spring having a first end arranged to act on the inner walling of the fluid conduit and a second end arranged to act on the plunger. In an example, the heat-sensitive element comprises a frangible bulb. In an example, the frangible bulb is an elongate glass bulb. The elongate frangible glass bulb may have a pointed end and a rounded end. In an example, the body defines a plurality of discharge orifices distributed equidistantly about a central axis of the body. In an example, the body comprises a lower body part in which the at least one discharge orifice is defined and an upper body part in which the fluid conduit is defined, the upper body part releasably connected to the lower body part. In an example, the upper body part comprises a coupling arrangement for facilitating installation of the nozzle within a support element. In an example, the coupling arrangement of the upper body part comprises one part of a two-part coupling. In an example, the coupling arrangement of the upper body part comprises a screw thread, which may be an external screw thread. In an example, the upstream side of the interior landing presenting an annular surface extending perpendicularly to the longitudinal axis of the fluid conduit. In an example, the downstream side of the interior landing and the plugging end of the plunger comprise corresponding first mating surfaces, for distributing a force between the plunger and the body over a first plane, and corresponding second mating surfaces, for distributing a force between the plunger and the body over a second, different plane. In an example, the downstream side of the interior landing presents a first annular mating surface portion extending perpendicularly to the longitudinal axis of the fluid conduit and radially outwardly from the passageway, and a second, frustoconical mating surface portion extending radially outwardly from the inner annular surface mating surface. In an example, the protuberance has a generally hemispherical tip. In an example, the plunger, when in the flow-preventing position, is configured to withstand a downward force of 150 Bar, without the seal between the plunger and the fluid conduit leaking and without the heat-sensitive element rupturing. According to a second aspect there is provided a water mist fire suppression system comprising the nozzle of the first aspect. According to a third aspect there is provided a method of providing a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system, comprising the steps of: providing the fluid conduit with an interior landing extending transversely with respect to a longitudinal axis of the fluid conduit, the interior landing defining a passageway extending therethrough between an upstream side and a downstream side of the interior landing, and providing a plugging end of the plunger with a protuberance and a profile to permit the mating of the downstream side of the interior landing, with the protuberance projecting through the passageway and beyond the upstream side of the interior landing, to provide a seal between the plunger and the fluid conduit. The present invention thus provides a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system. The present invention provides a nozzle for a water mist fire suppression system comprising the seal, and thus embodying the present invention. The present invention further provides a water mist fire suppression system comprising at least one nozzle embodying the present invention. The present invention also provides a method providing a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system. While the present invention is disclosed herein in the context of a nozzle for a water mist fire suppression system, it may be embodied without inventive activity in a nozzle for an alternative type of water-based fire suppression system. It is thus to be appreciated that the suitability of a nozzle embodying the present invention for use in a water-based fire suppression system may not be limited to the specific application of a water mist fire suppression system. Further particular and preferred aspects of the invention are set out in the accompanying dependent claims. Brief Description of the Drawings The present invention will now be more particularly described, with reference to the accompanying drawings, in which: Figure I shows a perspective view of a prior art water mist nozzle; Figure 2 shows a cross-sectional view of the prior art water mist nozzle of Figure I ; Figure 3 shows a perspective view of an example water mist nozzle embodying the present invention; Figure 4 shows a cross-sectional view of the water mist nozzle of Figure 3; Figure 5 illustrates components of the water mist nozzle of Figure 3, in a flow preventing arrangement; Figure 6 illustrates components of the water mist nozzle of Figure 3, in a flow permitting arrangement; and Figure 7 shows an exploded view of the water mist nozzle of Figure 3. Description Illustrative embodiments and examples are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the apparatus described herein. It is to be understood that embodiments and examples can be provided in many alternate forms and the invention should not be construed as limited to the embodiments and examples set forth herein but by the scope of the appended claims. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. In addition, features referred to herein in the singular can number one or more, unless the context clearly indicates otherwise. Similarly, the terms “comprises”, “comprising”, “includes”, “including”, “has” and / or “having” when used herein, specify the presence of the stated feature or features and do not preclude the presence or addition of one or more other features, unless the context clearly indicates otherwise. In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention, unless the context clearly indicates otherwise. The drawings are not necessarily drawn to scale, and in some instances the drawings may have been exaggerated or simplified for illustrative purposes only. Figure I shows a perspective view, and Figure 2 a cross-sectional view, of a prior art water mist nozzle I, features of a specific example of which will now be described. The water mist nozzle I comprises a body 2, which has a central axis CA. The body 2 has a first, upper end 3, for installation within a support element (not shown), such as a ceiling or mounting fixture for a ceiling, and a second, lower end 4. The body 2 defines a fluid conduit 5, which extends between a fluid inlet 6 and a fluid outlet 7, the fluid inlet 6 for connection to a supply of water, in use. The body 2 also defines at least one discharge orifice 8. According to the specific illustrated design, the body 2 defines a plurality of discharge orifices 8 distributed equidistantly about the central axis CA of the body 2. In the specific example shown, the body 2 defines four of the discharge orifices 8. The water mist nozzle I comprises a flow control arrangement for controlling flow through the fluid outlet 7. As will be described in further detail below, in use, the water mist nozzle I is normally held in a "closed" condition, in which flow through the fluid outlet 7 is prevented, and configured to enter an "open" condition, to allow flow through the fluid outlet 7, upon detecting a temperature exceeding an activation temperature threshold. The flow control arrangement of water mist nozzle I comprises a plunger 9 and a heatsensitive element 10. According to the specific illustrated design, heat-sensitive element 10 is an elongate frangible bulb. The plunger 9 is movable relative to the fluid conduit 5 between a flow-preventing position, to seal the fluid conduit 5, and a flow-allowing position, to unseal the fluid conduit 5. In Figure 2, the plunger 9 is shown in the flow-preventing position. The plunger 9 is movable in the direction indicated by arrow T from the flow-preventing position, which the plunger 9 is maintained in during the water mist nozzle I being held in a "closed" condition, into the flow-allowing position, to open the fluid conduit 5. As can be seen in Figure 2, arrow T indicates a downstream direction. According to the specific illustrated design, the direction indicated by arrow T is along the central axis CA of the body 2. The heat-sensitive element 10 is configured to rupture in response to exposure to a temperature exceeding an activation temperature threshold. In an example, the activation temperature threshold is 56 degrees Celsius. The flow control arrangement is configured to maintain the plunger 9 in the flow-preventing position while the heat-sensitive element 10 remains unruptured, and to allow the plunger 9 to move to the flow-allowing position upon rupture of the heat-sensitive element 10. According to the specific illustrated design, the plunger 9 and the heat-sensitive element 10 have interfacing first ends II, 12. The first end 12 of the heat-sensitive element 10 is shown seated in a location recess 13 provided in the first end I I of the plunger 9 for it. The heatsensitive element 10 has a second end 14 that interfaces with a support portion 15 of the body 2. According to the specific illustrated example, the support portion 15 is provided by a grub screw that is releasably engaged in a threaded channel 16 provided in the second, lower end 4 of the body 2. The plunger 9 has a second end 17 that is profiled to interface with inner walling 18 of the fluid conduit 5. As can be seen in Figure 2, the fluid conduit 5 opens into an interior zone, indicated by arrow 19, of the body 2, in which the plunger 9 is received and movable. Disposed longitudinally between the first end I I and the second end 17 of the plunger 9 is a main body portion 20 having a diameter of a magnitude for achieving a close-fitting within the body 2. The inner walling 21 of the interior zone 19 of the body 2 presents a radially-inwardly extending shoulder 22 for limiting travel of the plunger 9 in the direction indicated by arrow T within the body 2. The main body portion 20 has an upstream-facing surface 23, which assists in forming water flowing through the fluid outlet 7 into a mist before exiting the body 2. According to the specific illustrated design, the body 2 comprises a lower body part 24 in which the at least one discharge orifice 8 is defined and an upper body part 25 in which the fluid conduit 5 is defined, the upper body part 25 releasably connected to the lower body part 24, in the shown example by a screw-thread coupling (any suitable alternative type of releasable coupling may be used in other examples). In the shown example, the upper body part 25 comprises a coupling arrangement 26 for facilitating installation of the nozzle within a support element (not shown), in the specific illustrated example the coupling arrangement 26 comprises a screw thread (any suitable alternative type of coupling arrangement, which may comprise one part of a two-part coupling may be used in other examples). The plunger 9 in sealing contact with the fluid conduit 5 is illustrated box A of Figure 2. When the plunger 9 is in the flow-preventing position (the water mist nozzle I being in the "closed" condition), as shown, corresponding mating surfaces 27, 28 of the second end 17 of the plunger 9 and the inner walling 18 of the fluid conduit 5 are in contact to provide a seal between them. According to the specific illustrated design, the mating surface 27 of the plunger 9 and the mating surface 28 of the fluid conduit 18 are both frustoconical. These frustoconical surface are able to be brought into sealing contact by the mating surfaces 27, 28 of the plunger 9 and fluid conduit 5 being provided as an external surface of a "male" component and as an internal surface of a "female" component respectively. As shown, according to this illustrated prior art design, the second end 17 of the plunger 9 presents a flat face 29, from which the mating surface 27 of the plunger 9 extends (radially outwardly and increasing in diameter with increasing distance in the downstream direction). The flat face 29 of the second end 17 of the plunger 9 is exposed to the interior of the fluid conduit 5. In a 'wet pipe' water mist fire suppression system, the fluid conduit 5 will always be charged with water, so that water is available to be issued through the discharge orifices 8 of the body 2 immediately following activation of the water mist nozzle I. Thus, in a 'wet pipe' system, when the water mist nozzle I is in the normally "closed" condition, the upstream-facing flat face 29 of the plunger 9 is directly exposed to pressurised water within the fluid conduit 5, the application of pressure on the flat face 29 of the plunger 9 by fluid in the fluid conduit 5 being indicated by arrow 30. The plunger 9 is held in contact with the fluid contact 5 by the unruptured heat-sensitive element 10. Upon rupture of the heat-sensitive element 10, either through proper functioning in response to exposure of heat exceeding its activation temperature threshold or through accidental or intentional damage, the plunger 9 is released from the flow-preventing position and allowed to move, in the direction indicated by arrow T, away from the fluid conduit 5, to break the contact between the mating surfaces 27, 28 of the plunger 9 and fluid conduit 5 and open the fluid conduit 5. Movement of the plunger 9 from the flow-preventing position is encouraged by the action of a compression spring (not shown) arranged to bias the plunger 9 towards the flow-allowing position. A problem has been identified with the illustrated prior art design in that pressure applied to the flat face 29 of the plunger 9 by water within the fluid conduit 5 is detrimental to achieving the objective of maintaining a watertight seal within the nozzle I while maintaining the integrity of the heat-sensitive element 10. The present invention provides a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system, and a nozzle for a water mist fire suppression system comprising the seal. A seal according to the present invention will now be described with reference to Figures 3 to 7, which illustrate an example nozzle 101 for a water mist fire suppression system embodying the present invention. Figure 3 shows a perspective view of nozzle 101. Figure 4 shows a cross-sectional view of nozzle 101, showing features of a specific example of a seal according to the present invention, provided between a plunger and a fluid conduit of the nozzle 101. In Figure 4, the nozzle 101 is shown in the normally "closed" condition. Figures 5 &6 illustrate components of the nozzle 101 in a flow preventing arrangement, in which the seal is made, and in in a flow permitting arrangement, in which the seal is unmade, respectively. Figure 7 shows an exploded view of components of the nozzle 101. The following description will focus on features of difference of the nozzle 101 of Figures 3 to 7 compared to the prior art nozzle I of Figures I &2, with the number series "200" being used to refer to like features and the number series "300" being used to refer to specific features of the nozzle 101 not found in the prior art nozzle I. From a comparison of the views shown in Figures I &3, the appearance of nozzle 101 corresponds to that of the prior art nozzle I. Comparing Figure 4 with Figure 2, nozzle 101 comprises a body 202 defining a fluid conduit 305, extending between a fluid inlet 206 for connection to a supply of water and a fluid outlet 207, and at least one discharge orifice 208. Nozzle 101 comprises a flow control arrangement for controlling flow through the fluid outlet 207. The flow control arrangement comprises a plunger 209, the plunger 209 movable relative to the fluid conduit 205 between a flowpreventing position, to seal the fluid conduit 205, and a flow-allowing position, to unseal the fluid conduit 205. The plunger 209 is movable in the direction indicated by arrow T from the flow-preventing position, to close the fluid conduit 205, into the flow-allowing position, to open the fluid conduit 205. The flow control arrangement comprises a heat-sensitive element 210 configured to rupture in response to exposure to a temperature exceeding an activation temperature threshold. According to this specific example, heat-sensitive element 210 is an elongate frangible glass bulb. The flow control arrangement is configured to maintain the plunger 209 in the flow-preventing position while the heat-sensitive element remains unruptured, 210 and allow the plunger 209 to move to the flow-allowing position upon rupture of the heat-sensitive element 210. Nozzle 101 incorporates a seal between the plunger 209 and the fluid conduit 205 that differs from that of prior art nozzle I. The plunger 209 in sealing contact with the fluid conduit 205 is illustrated box A of Figure 4. The fluid conduit 205 has a longitudinal axis, which in this specific example is aligned with central axis CA of the body 202. The fluid conduit 205 comprises a transversely extending interior landing, 301. The interior landing 301 defines a passageway 302 therethrough, which extends between an upstream side 303 of the interior landing 301 and a downstream side 304 of the interior landing 301. The plunger 209 comprises a second, plugging end 217 having a protuberance 305. The plugging end 217 of the plunger 209 is profiled to mate with the downstream side 304 of the interior landing 301, with the protuberance 305 projecting through the passageway 302 and beyond the upstream side 303 of the interior landing 301, for providing a seal between the plunger 209 and the fluid conduit 205 when the plunger 209 is in the flow-preventing position. When the plunger 209 is in the flow-preventing position (the nozzle I being in the "closed" condition), as shown, corresponding mating surfaces, indicated generally at 306, 307, of the plunger 209 and the interior landing 301 of the fluid conduit 205 are in contact to provide a seal between them. The upstream side 303 of the interior landing 301 presents an annular surface 308 that extends perpendicularly to the longitudinal axis of the fluid conduit 205. The annular surface 308 extends radially outwardly of the passageway 302 to the inner walling 218 of the fluid conduit 205. The annular surface 308 of the upstream side 303 provides a reduction in the diameter of the fluid conduit 205. According to this specific example, the annular surface 308 is flat, extends normal to the central axis CA of the body 202, and has a circular outer edge and a circular inner edge around the opening of the passageway 302 to the upstream side 303. With the specific illustrated design, the protuberance 305 of the plunger 209 has a curved tip 309. According to this specific example, the plunger 209 has a generally hemispherical tip 309. Notably, with the specific illustrated design, the downstream side 304 of the interior landing 301 and the plugging end 217 of the plunger 209 comprise corresponding first mating surfaces, indicated at 309, 310, for distributing a force between the plunger 209 and the body 202 over a first plane, indicated by arrow PI, and corresponding second mating surfaces, indicated at 311,312, for distributing a force between the plunger 209 and the body 202 over a second, different plane, P2. According to this specific example, the downstream side 304 of the interior landing 301 presents a first annular mating surface portion 310 extending perpendicularly to the longitudinal axis of the fluid conduit 205 and radially outwardly from the passageway 302, and a second, frustoconical mating surface portion 312 extending radially outwardly from the inner annular surface mating surface 310. Thus, according to this specific example, and as can be seen in Figure 4 in particular, the first annular mating surface portion 3 10 of the downstream side 304 extends parallel to the annular surface 308 of the upstream side 303 of the interior landing 301. In Figure 5, the heat-sensitive element 210 is shown unruptured (intact) and operating to maintain the plunger 209 in the flow-restraining position in which the fluid conduit 205 is blocked and flow is prevented. In Figure 6, the heat-sensitive element 210 is shown ruptured (broken) and no longer operating to maintain the plunger 209 in the flow-restraining position in which flow through the fluid conduit 205 is blocked; the plunger 209 having moved in the direction indicated by arrow T, away from the interior landing 301, into a flow-allowing position in which the fluid conduit 205 is unblocked and flow is permitted. The exploded view of Figure 7 shows upper and lower parts 224, 225 of the body 202, plunger 209, heat-sensitive element 210 and support portion 215, such components of the nozzle 101 having already been mentioned. Also shown is a biasing element 701 of the flow control arrangement, for resiliently biasing the plunger 209 towards the flow-allowing position. According to this specific example, the biasing element 701 is a compression spring having a first end 702 arranged to act on the inner walling 218 of the fluid conduit 205 and a second end 703 arranged to act on the plunger 209. In an example the upper and lower parts 224, 225 of the body 202, plunger 209, support portion 215, and biasing element 701 comprise stainless steel, and the frangible bulb comprises glass. The annular mating surface portion 3 10 of the upstream side 303 of the interior landing 301 in effect reduces the diameter of the fluid conduit 205 to that of the passageway 302 and reduces the area of the plunger 209 that is exposed to the interior of the fluid conduit 205. Thus, the annular mating surface portion 310 of the upstream side 303 of the interior landing 301 functions to shield an area of the plunger 209 from the pressure of fluid in the fluid conduit 205 upstream. Further, only the tip 309 of the protuberance 305 of the plunger 209, this being inserted through the passageway 302 of the interior landing 301 of the fluid conduit 205 to project from the upstream side 303 of the interior landing 301, is exposed to the interior of the fluid conduit 205 upstream and hence to the pressure of fluid in the fluid conduit 205. The curvature of the tip 309 of the protuberance 305 functions to distribute the pressure of fluid in the fluid conduit 205 around it, diverting force away from being applied directly downward onto the plunger 209. The seal of the present invention advantageously relieves the second, plugging end of the plunger 209 of load acting in a downstream direction to push the plunger 209 away from the fluid conduit 205, in particular from pressurised water upstream of the plunger 209, whilst still providing a fluid outlet 207 that is sufficiently dimensioned to permit an acceptable throughout of water from the fluid conduit 205 for egress from the discharge outlets 208 to suppress a fire. Specific Example - Results of Testing A specific example of a nozzle comprising a seal according to the present invention was tested in accordance with the current British Standard BS 8663-1:2019 Fixed fire protection systems. Components for watermist systems. Specification and test methods for watermist nozzles. The nozzle was assembled vertically, with the piston (plunger) inserted under the coupling (upper body part), the frangible glass bulb (heat-sensitive element) inserted under the piston (plunger) and the grub screw (support portion) inserted under the frangible bulb (heatsensitive element). A load was applied to the grub screw, with the resistance to that load applied at the top of the piston (plunger) against the sealing face of the coupling. The frangible glass bulb (heat-sensitive element) was a 3 mm x 16 mm glass bulb having a nominal operating temperature of 57 °C, available from Norbulb Sprinkler Elemente GmbH (Norbulb N3). The diameter of the upstream side of the interior landing was 9 mm and the diameter of the passageway through the interior landing was 3 mm. Preliminary tests were conducted together to determine if the sealing faces (between the piston (plunger) and the coupling (upper body part) can resist a predetermined magnitude of pressure without stressing the frangible glass bulb (heat-sensitive element) or fracturing it. The purpose of this testing stage was to ensure that the glass bulb was not over stressed, to pass the leak test and then to pass the bath test, as over stressing the glass bulb to achieve a watertight seal can cause activation outside the test parameters. Leak Test Four nozzles were used in this test. This test involves subjecting each nozzle, at the inlet, to a pressure of 1.5 times the maximum operating pressure (150 Bar). To pass the test, a watertight seal must be achieved without the frangible glass bulb (heat-sensitive element) breaking or being subjected to too high a force. The sealing faces of the piston (plunger) and the coupling (upper body part) were closed tight by means of the grub screw (support portion) being rotated in a tightening direction, to travel upwards towards the coupling (upper body part), to apply a force through the frangible glass bulb (heat-sensitive element) to the piston (plunger). The force is measured in cNm, with the recommended force on the frangible glass bulb (heat-sensitive element) being 26 cNm. Bath Test Thirty nozzles (three sets of ten) were used in this test. This test involves immersing each nozzle in a water bath and steadily heating the nozzle to the operating temperature of the glass bulb (nominally 57 °C). To pass the test, the glass bulbs must activate within a prescribed temperature range associated with the rating of the glass bulb. Identifying a “Fail” If any of the 4 nozzles used in the Leak Test did not achieve a watertight seal or if any of the 30 nozzles used in the Bath Test activated outside of the prescribed temperature range, this was recorded as a “Fail”. In the event of a “Fail”, re-testing is conditional on a demonstratable change to the nozzle design. Results All the nozzles used in the Leak Test passed. Of note, a force of 25 cNm on the frangible glass bulb (this being lower than the recommended force) and a pressure of 200 Bar (this being higher than 1.5 times the maximum operating pressure) was achieved. All the nozzles used in the Bath Test passed. Additional Testing Further testing was performed to check that when the nozzle is activated under a fire condition, the flow egressing the nozzle is sufficient to activate a flow switch and signal a fire pump to engage. Flow Rate Test This test involves heating the nozzle in an oven at a predetermined temperature (800 degrees) for a specified time, following which it is quenched and then run at an operating pressure (100 Bar). To pass the test, the nozzle must deliver a specified K factor (0.8) of flow (8 litres of water per minute (8 litres / min)). Identifying a “Fail” If the flow egressing the nozzle was less than 8 LPM, this was recorded as a “Fail”. Results Each nozzle tested passed. The body of the nozzle may define any suitable number of discharge orifices of any one or more shape and / or size and that a plurality of discharge orifices of the body may be distributed in any suitable arrangement. The body of the nozzle may comprise parts that are connectable, optionally and / or as appropriate releasably connectable, utilising any suitable alternative way of connection or type of releasable coupling to that specifically mentioned herein. The present invention provides a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system, and provides a nozzle for a water mist fire suppression system comprising the seal. A water mist fire suppression system comprising at least one nozzle comprising the seal of the present invention is also provided. The present invention further provides a method of providing a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system, comprising the steps of: providing the fluid conduit with an interior landing extending transversely with respect to a longitudinal axis of the fluid conduit, the interior landing defining a passageway extending therethrough between an upstream side and a downstream side of the interior landing, and providing a plugging end of the plunger with a protuberance and a profile to permit the mating of the downstream side of the interior landing, with the protuberance projecting through the passageway and beyond the upstream side of the interior landing, to provide a seal between the plunger and the fluid conduit. Thus, a seal is provided between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system. The fluid conduit is provided with an interior landing extending transversely with respect to a longitudinal axis of the fluid conduit, the interior landing defining a passageway extending therethrough between an upstream side (303) and a downstream side of the interior landing. A plugging end of the plunger is provided with a protuberance and a profile to permit mating with the downstream side of the interior landing, such that, when mated, the protuberance projects through the passageway and beyond the upstream side of the interior landing, to provide the seal. Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and / or described and that 5 various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

I. A nozzle for a water mist fire suppression system, the nozzle comprising:a body defining a fluid conduit, extending between a fluid inlet for connection to a supply of water and a fluid outlet, and at least one discharge orifice, anda flow control arrangement for controlling flow through the fluid outlet, the flow control arrangement comprising:a plunger movable relative to the fluid conduit between a flow-preventing position, to seal the fluid conduit, and a flow-allowing position, to unseal the fluid conduit, anda heat-sensitive element configured to rupture in response to exposure to a temperature exceeding an activation temperature threshold,the flow control arrangement configured to:maintain the plunger in the flow-preventing position while the heat-sensitive element remains unruptured, andallow the plunger to move to the flow-allowing position upon rupture of the heatsensitive element;the fluid conduit having a longitudinal axis and comprising a transversely extending interior landing, the interior landing defining a passageway extending therethrough between an upstream side and a downstream side of the interior landing, andthe plunger comprising a plugging end having a protuberance,the plugging end of the plunger profiled to mate with the downstream side of the interior landing, with the protuberance projecting through the passageway and beyond the upstream side of the interior landing, for providing a seal between the plunger and the fluid conduit when the plunger is in the flow-preventing position.

2. The nozzle of claim I, the heat-sensitive element having a first end to interface with the plunger and a second end to interface with the body of the nozzle.

3. The nozzle of claim I or claim 2, the flow control arrangement comprising a biasing element for resiliently biasing the plunger towards the flow-allowing position.

4. The nozzle of claim 3, in which the biasing element is a compression spring having a first end arranged to act on the inner walling of the fluid conduit and a second end arranged to act on the plunger.

5. The nozzle of any one of claims I to 4, the heat-sensitive element comprising a frangible bulb.

6. The nozzle of any one of claims I to 5, the body defining a plurality of discharge orifices distributed equidistantly about a central axis of the body.

7. The nozzle of any one of claims I to 6, the body comprising a lower body part in which the at least one discharge orifice is defined and an upper body part in which the fluid conduit is defined, the upper body part releasably connected to the lower body part.

8. The nozzle of claim 7, the upper body part comprising a coupling arrangement for facilitating installation of the nozzle within a support element.

9. The nozzle of any one of claims I to 8, the upstream side of the interior landing presenting an annular surface extending perpendicularly to the longitudinal axis of the fluid conduit.

10. The nozzle of any one of claims I to 9, the downstream side of the interior landing and the plugging end of the plunger comprising corresponding first mating surfaces, for distributing a force between the plunger and the body over a first plane, and corresponding second mating surfaces, for distributing a force between the plunger and the body over a second, different plane.I I. The nozzle of claim 10, the downstream side of the interior landing presenting a first annular mating surface portion extending perpendicularly to the longitudinal axis of the fluid conduit and radially outwardly from the passageway, and a second, frustoconical mating surface portion extending radially outwardly from the inner annular surface mating surface.

12. The nozzle of any one of claims I to I I, the protuberance having a generally hemispherical tip.

13. The nozzle of any one of claims I to 12, the plunger, when in the flowpreventing position, configured to withstand a downward force of at least 150 Bar, without the seal between the plunger and the fluid conduit leaking and without the heat-sensitive element rupturing.

14. A water mist fire suppression system comprising the nozzle of any one of claims I to 13.

15. A method of providing a seal between a plunger and a fluid conduit of a nozzle for a water mist fire suppression system, comprising the steps of:providing the fluid conduit with an interior landing extending transversely with respect to a longitudinal axis of the fluid conduit, the interior landing defining a passageway extending therethrough between an upstream side and a downstream side of the interior landing, andproviding a plugging end of the plunger with a protuberance and a profile to permit the mating of the downstream side of the interior landing, with the protuberance projecting through the passageway and beyond the upstream side of the interior landing, to provide a seal between the plunger and the fluid conduit.

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