The invention relates to a nozzle and particularly to a nozzle for a firewater monitor. The invention further relates to a firewater monitor and a firewater system comprising such nozzle.

Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). A water hammer commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. It is also called hydraulic shock. This pressure wave can cause major problems, from noise and vibration to pipe collapse. It is possible to reduce the effects of the water hammer pulses with accumulators, expansion tanks, surge tanks, and other features. An application area where water hammer is a severe problem is firefighting using firewater monitors. A firewater monitor is a device used to supress a fire in a fire hazard area. The firewater monitor is typically located away from the area it protects, and can cover the area by a water spray or a water jet from a distance to the fire. Typically, the firewater monitor can be located 20 to 40 meter away from the area it protects. The monitor can be rotated, and the elevation angle of the water discharge can be adjusted up or down. The firewater monitor can be remotely operated by use of hydraulic or electrical remote control, it can be arranged with an oscillating device, which will cause it to oscillate over a preset sector, or it can be purely manually operated. The water piping is empty (dry pipe end section) when the system is activated. Because of the lack of backpressure as the water piping is filled up, the flow velocity of the water column front as it is travelling through the empty piping can be 2 to 3 times the flow velocity under normal operational conditions. The water hammer will then occur when the water column hits the sudden reduction in cross-section flowing area represented by the monitor nozzle. Water hammer for such systems can get very high. Peak pressure of up to 100 bar has been experienced. The longer this dry pipe section, the bigger the water hammer effect, which is the reason that in the prior art, the dry pipe sections (between the last release valve and the monitor) are generally kept short (which is not desired for firefighting as you cannot get close to the fire), or dedicated expensive valve systems very near to the end of the piping are used.

In non-prepublished patent application PCT/NO2015/050158 owned by the same applicant, the water hammer problem is tackled with a safety device at a downstream side of the system. The safety device, which in one of its embodiments is placed within the end section of a fluid piping, comprises a diffuser placed in a centre region of the fluid column in operational use for redirecting fluid from the centre region of the fluid column to the outside. This safety device has been specifically designed in view of reducing water hammer in piping systems having an end section which is normally dry (when not used), and which is rapidly filled up upon release of a deluge valve or a system release valve. Such device is typically installed at the end of each piping leg, where there is a fire monitor, or other device, which represents a sudden significant reduction in cross-section flow area. The safety device is typically installed at the end of each piping leg in a firewater system and its purpose is to reduce the flow velocity of the water column, before it hits the firewater monitor or other device that has a significant smaller cross section flowing area. In operational use of the safety device within a fluid piping the diffuser in the centre region changes the moving direction of the incoming fluid, which slows down the fluid column before it hits a tap or a firewater monitor, for example, that is mounted downstream of the diffuser at the end of the piping. It has been verified that the flow speed can be reduced with 40% to 50% using this safety device. Placing the diffuser in the centre region is particularly effective because the flow speed within a fluid piping is typically highest in the centre region. The effective flow cross-sectional area is yet also a little bit reduced, but this gives only a small pressure drop at nominal fluid flow (typically at 5 to 10 bar). What is meant with the terms "upstream" and "downstream" is further illustrated in the description of the figures, yet such terms are quite common terms for the person skilled in the art. Even though the results with this safety device were already impressive, there was still a remaining water hammer effect, which is the context of the current invention.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow. The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect the invention relates to an nozzle for a firewater monitor. The nozzle is configured for being coupled to an inlet piping having an inlet flow area. The nozzle has an outlet, wherein the outlet has an outlet flow area. The nozzle is configured for having a standby mode and a throttle mode in operational use, wherein, in the standby mode, the outlet flow area has a size similar to the inlet flow area. The nozzle is configured for gradually throttling the outlet when, in the throttle mode in operational use, fluid is flowing through the outlet.

The effects of the nozzle in accordance with the invention are as follows. The nozzle of the invention has a standby mode, wherein the outlet flow area is substantially similar to the inlet flow area. The advantage of this feature is that when the liquid starts to flow and hit the nozzle it experiences hardly any obstruction and therefore the water surge pressure is strongly reduced. Then the nozzle is configured such that as soon as the fluid starts to flow through the outlet the nozzle gradually throttles the outlet. It has been found out that a throttling time, measured from fully open in standby position to full throttling in throttling mode, ranging between two and five seconds gives satisfactory results. The gradual throttling effect, which is triggered after that, the fluid starts to leave the outlet of the nozzle, ensures that no significant surge pressure is built up.

In order to facilitate understanding the invention a few expressions are defined hereinafter.

Wherever the wording "nozzle" is used, this refers to a device which can be operated over a wide range from a straight water jet to a wide fog position ( typically with a spray angle of 120 to 150 degrees). The nozzle has typically a significantly lower flow area than the piping arrangement upstream of the nozzle. Typically the flow area in the nozzle is 7 - 15 % of the flow area of the piping lying upstream of the nozzle. The purpose of the reduced flow area is to obtain a certain pressure upstream the nozzle ( typically 5 - 9 Bar) to be able to achieve a significant throw length in jet position (typically for a monitor nozzle this is between 50 and 70 meters). The nozzle must also be able to produce a water fog, when the nozzle is in the so-called wide fog position. The throw length in the wide fog position is typically between 5 and 10 meters.

Wherever the wording "flow area" is used, this refers to the cross-sectional area of the respective part measured in a plane perpendicular to the flow direction. Wherever the wording "inlet flow area" is used, this refers to the flow area of the last segment of the piping before the nozzle. This could be the end section of the firewater monitory body onto which the nozzle is mounted.

Wherever the wording "outlet flow area" is used, this refers to flow area of the outlet of the nozzle where the fluid leaves the nozzle.

Wherever the word "fluid" is used, this must be interpreted as including liquid, gas, and anything else that is fluid and can be transported through a piping. In firewater monitors water is often used for extinguishing fires, but the invention is not limited to such application per se.

The feature "the outlet flow area has a size similar to the inlet flow area" has to be interpreted such that the outlet flow area does not deviate more than 25% from the inlet flow area in both directions.

In an embodiment of the nozzle in accordance with the invention the nozzle is configured for using pressure of the fluid in the nozzle for gradually throttling the outlet in the throttle mode. Using the pressure of the fluid to throttle the fluid flow is advantageous, because no external force and energy source is then necessary. Throttling a fluid flow, which is under high pressure, does cost a certain amount of force and energy.

In an embodiment of the nozzle in accordance with the invention, in the standby mode of the nozzle, the outlet flow area has a size, which is between 80% and 90% of the inlet flow area. The inventor has discovered that an outlet flow area in the range of this embodiment gives the best results. In embodiments using the water pressure to trigger and drive the throttling mechanism it is beneficial to have a reduction in flow area in order to build up a certain pressure upstream of the nozzle. It is this pressure that will cause the nozzle to gradually push the "second tubular member" of the nozzle over in the throttled flow position. If the nozzle has the same flow area as the upstream piping, there will be no pressure build up, and hence no available force for the nozzle to change position.

In an embodiment of the nozzle in accordance with the invention, in the throttle mode the outlet flow area has a minimum size between 10% and 20% of the inlet flow area. The reduction in flow area in the nozzle compared to the upstream piping is necessary to get significant nozzle pressure to achieve the required nozzle performance in terms of water throw length in straight jet position, and water fog quality (water droplet size) in wide fog position. In an embodiment of the nozzle in accordance with the invention the nozzle is provided with an expandable chamber, which is in fluid communication with the outlet such that an increasing pressure in the outlet leads to the fluid gradually filling and expanding the expandable chamber to obtain an expansion thereof, wherein the nozzle is further configured such that the expansion of the expandable-chamber controls a reduction of the outlet flow area for throttling the outlet. This embodiment constitutes a very convenient and efficient way of using the fluid pressure to throttle the embodiment. More details of a possible implementation are given in the detailed description of the figures. The fluid communication between outlet and expandable chamber can be arranged via one or more feed channels implemented in the inner wall of the outlet of the nozzle, wherein the one or more feed channels lead from the inner side of the nozzle to the expandable chamber. The configuration (for instance the flow area of the feed channels) of these feed channels determines the flow speed and flow quantity of the fluid to the expandable chamber and thereby the throttling speed. More details on the implementation of the feed channels are given in the detailed description of the figures.

In an embodiment of the nozzle in accordance with the invention the expandable chamber is resiliently loaded in that it tends to go back to a smaller volume when the pressure in the outlet drops. This embodiment conveniently switches the nozzle back to the standby mode, when the fluid pressure drops or when the fluid flow is completely stopped. At the same time the resilient loading of the expandable chamber enables to control the throttling behaviour of the nozzle.

In an embodiment of the nozzle in accordance with the invention the nozzle is provided with a first hollow member and a second hollow member placed one within the other and being movable relative to each other, which form a variable length telescopic assembly, wherein the expandable chamber is defined by an annular space formed in between said hollow members when said hollow members move away from each other. In order to define expandable, that is to say a variable length, chamber in a telescopic assembly the telescope members are preferably shaped with a non-uniform diameter over their length such that the variable length chamber can be defined where the diameter transits from a smaller to a large diameter. More details of a possible implementation are given in the detailed description of the figures.

In an embodiment of the nozzle in accordance with the invention the expandable chamber is spring loaded by a plurality of springs distributed around the circumference of the nozzle and arranged in between the first hollow member and the second hollow member. More details of a possible implementation are given in the detailed description of the figures.

In an embodiment of the nozzle in accordance with the invention the nozzle is provided with an axially-placed nozzle baffle at a downstream end of the nozzle such that the outlet flow area is defined by the annular space between the axially-placed nozzle baffle member and an inner wall of the outlet at the downstream end, wherein the axially-placed nozzle baffle is configured for redirecting the fluid from a centre region to the outside. Nozzle baffles are commonly used in nozzles. The inventor has found a convenient way to control the outlet flow area defined between this nozzle baffle and the outlet. More details of a possible implementation are given in the detailed description of the figures.

In an embodiment of the nozzle in accordance with the invention the nozzle is further provided with a telescopic jet head at the downstream end of the nozzle, wherein the telescopic jet head is configured for cooperating with the axially-placed nozzle baffle to form a fluid jet beam in operational use when being extended. The telescopic jet head is not part of the invention as such, but can be conveniently combined with the invention as in this embodiment. More details of a possible implementation are given in the detailed description of the figures.

In a second aspect the invention relates to a firewater monitor comprising the nozzle in accordance with the invention. Firewater monitors form a first important application field of the nozzle of the invention. Such devices typically are mounted on pipings, which are dry in standby and the pressure surges are high, when these devices are taken into operational use.

An embodiment of the firewater monitor in accordance with the invention further comprises:

a firewater monitor body for being mounted on a feed pipe flange, and

a fixing flange arrangement for fixing the firewater monitor onto the feed pipe flange. This embodiment gives some further implementation details of a certain type of firewater monitor.

An embodiment of the firewater monitor in accordance with the invention further comprises a joint assembly provided in the firewater monitor body for allowing directing the firewater monitor to a specific fire location. This embodiment gives some further implementation details of a certain type of firewater monitor. In an embodiment of the firewater monitor in accordance with the invention the joint comprises: i) a first full bore swivel joint provided in the firewater monitor body for allowing horizontal rotation of the firewater monitor, and ii) a second full bore swivel joint provided in the firewater monitor body for allowing vertical rotation of the firewater monitor. This embodiment gives some further implementation details of a certain type of firewater monitor. The swivel joints are preferably full bore, which means that they have the same flow area as the pipe section upstream of the monitor. The cross section flow area in the monitor is normally the same size as the feed pipe to the monitor, or maximum on standard piping dimension less. The purpose is to reduce the pressure drop in the piping from the monitor valve station to the monitor nozzle as much as possible. The ideal nozzle pressure ranges is approximately seven bar (but may range from five to nine bar).

In a third aspect the invention relates to a firewater system comprising a piping end section for releasing firewater for extinguishing fires and a nozzle in accordance the invention, wherein the nozzle is provided at the end of the piping end section. The invention finds application in other systems also, for instance where the nozzle is fixedly directed in a direction of a place having fire hazard, for instance for protection of high risk fire objects containing large volumes of combustible fluids or gases or such objects under high pressure.

In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

Fig. 1 shows a nozzle in accordance with an embodiment of the invention;

Fig. 2 shows a cross-sectional view of the nozzle of Fig. 1 when in standby mode;

Fig. 3 shows a cross-sectional view of the nozzle of Fig. 1 when in throttle mode;

Fig. 4 shows a cross-sectional view of the nozzle of Fig. 1 when in jet beam mode;

Fig. 5 shows a side view of the nozzle of Fig. 1 ;

Fig. 6 shows a front view of the upstream side of the nozzle of Fig. 1 ;

Fig. 7 shows a firewater monitor system comprising a firewater monitor comprising the nozzle of Fig. 1 , and

Fig. 8 shows a partial view of the firewater monitor of Fig. 7. In the embodiments described hereinafter there is a strong focus on firewater systems. However, the invention is not limited to such systems at all. The invention may be applied to any fluid system, but is particularly useful for water systems having a dry end pipe section when not operationally used. When operationally used such dry end pipe sections are typically rapidly filled up with a water column that travels at high speed and thus may hit the monitor or other end device with that same high speed. Thus, at all places where the word "water" is used this may be replaced with "fluid", including any liquid or gas, or mixtures thereof.

Fig. 1 shows a nozzle 100 in accordance with an embodiment of the invention. The nozzle 100 comprises a telescopic assembly 10Ots. The telescopic assembly 100ts comprises of three tubular members 100-1 , 100-2, 100-3 (hollow members) being slideable over and in each other to form the telescopic assembly 10Ots. Between the first tubular member 100-1 and the second tubular member 100-2 there is provided an expandable cover member 120 (in this embodiment bellows) annularly enclosing the telescopic assembly 10Ots. When the first tubular member 100-1 and the second tubular member 100-2 move relative to each other, the expandable cover member 120 will keep the nozzle 100 closed such that no fingers of the operator can get in between said members 100-1 , 100-2. Each of these members 100-1 , 100-2, 100-3 will be further explained with reference to the following figures. Fig. 1 further illustrates what is meant with upstream side 100us and downstream side 100ds of the nozzle 100. The downstream side 100ds is the side having an outlet 1 15. In the outlet 1 15 there is provided a nozzle baffle 1 10. Between the nozzle baffle 1 10 and the rim of third tubular member 100-3 there is defined the outlet flow area 1 15fa. Fig. 1 further illustrates a jet beam control lever 130, which controls the relative position of the third tubular member 100-3 (also referred to as the telescopic jet head) with regards to the second tubular member 100-2.

Fig. 2 shows a cross-sectional view of the nozzle 100 of Fig. 1 when in standby mode SBM. The standby mode SBM implies that there is no fluid flowing through the nozzle 100 and no pressure is present within the nozzle. The figure illustrates in further detail how the respective tubular members 100-1 , 100-2, 100-3 are built up to form the telescopic assembly. The tubular members 100-1 , 100-2, 100-3 may each comprise sub-parts, wherein said sub-parts are connected to form a single assembly. In this embodiment it is visible that the first tubular member 100-1 comprises of two sub-parts. The same applies to the second tubular member 100-2. The third tubular member 100-3 is formed of one piece. Hatching has been used in the drawing to illustrated, which sub-parts belong to the respective tubular members 100-1 , 100-2, 100-3. The second tubular member 100-2 is con- figured to slide over part of the first tubular member 100-1 , and the third tubular member 100-3 is configured to slide over part of the second tubular member 100-2. As Fig. 2 shows, in the standby mode SBM the length of the telescopic assembly is shortest, i.e. all tubular members are slid over their counter-part to the maximum extent. The result of this is that the outlet flow area 1 15fa is maximum as illustrated. Figs. 2 to 4 also show various O-rings as part of the telescopic assembly, which have not been indicated with reference numerals in order not to obscure the invention. It is considered to be well known to the person skilled in the art of telescopic nozzles that O-rings may be used to make the parts water tight.

This figure illustrates that the nozzle baffle 1 10 is fixedly mounted to the nozzle via a nozzle centre shaft 1 1 1 using a screw 1 18, i.e. it is not movable relative to the nozzle 100. The nozzle centre shaft 1 1 1 is kept in place via a nozzle body insert 1 12 (or centre shaft guide) and a spacer 1 19 (of which only one arm is shown in the cross-section). Fig. 2 further illustrates that the nozzle 100 has a nozzle inlet 101 having a nozzle inlet flow area 101 fa defined in between the nozzle centre shaft 1 1 1 and the first tubular member 100-1 . The nozzle inlet flow area 101 fa is typically chosen the same as the inlet flow area of the firewater monitor tubing (illustrated with reference to Fig. 8), but might also deviate from it.

Fig. 2 also illustrates a plurality of feed channels 103 in the inner wall of the first tubular member 100-1 , which lead to an interface between the first tubular member 100-1 and the second tubular member 100-2 as illustrated.

The function of the feed channels 103 is discussed with reference to Fig. 3 showing a cross-sectional view of the nozzle 100 of Fig. 1 when in throttle mode TM. The feed channels 103 are shaped such that, even at minimum length there is a small annular volume 105 at the interface between the first tubular member 100-1 and the second tubular member 100-2. When the nozzle is taken into operational use fluid is flowing through the nozzle towards the outlet 1 15. While the fluid pressure is being built up in the nozzle 100, (because of the slight reduction in flow area between the inlet piping (Fig. 8, ref 212) and the nozzle 100) fluid is being pressed in feed channels 103 entering the annular space (as indicated by the large bent arrow) and pressing the second tubular member 100-2 away from the first tubular member 100-1 as indicated by the small horizontal arrow. By doing so an expandable chamber 105 is formed at this interface. Fig. 3 illustrates the nozzle at maximum size of the expandable chamber 105. During this movement the second tubular member 100-2 moves closer to the nozzle baffle 1 10 thereby reducing the outlet flow area to a minimum 1 15fa'. The resulting liquid beam thereby changes into a fog beam FB as illustrated by the arrow at the outlet (in particular when liquid such as water is used).

Fig. 2 and 3 also show the plurality of springs 107 distributed along the circumference of the nozzle for spring loading the first tubular member 100-1 with respect to the second tubular member 100-2. The tubular members 100-1 , 100-2 and the springs are configured such that the springs 107 will try to push the second tubular member 100-2 over the first tubular member 100-1 towards minimum length. In throttle mode TM, the liquid pressure has to overcome the spring force.

Fig. 4 shows a cross-sectional view of the nozzle 100 of Fig. 1 when in jet beam mode JBM. The jet beam mode is for creating a parallel jet beam JB as illustrated. The second tubular member 100-2 and the third tubular member 100-3 have been moved away from each other, such that the end portion of the third tubular member 100-3 forces the beam to become parallel as illustrated.

Fig. 5 shows a side view of the nozzle 100 of Fig. 1 . Fig. 6 shows a front view of the upstream side of the nozzle 100 of Fig. 1 . Similar parts have similar reference numerals. Fig. 6 illustrated that the nozzle body insert 1 12 is configured as a guide having three radial arms extending outward.

Fig. 7 shows a firewater monitor system 1 comprising a firewater monitor 200 with the nozzle 100 of Fig. 1 . The system 1 comprises a feed pipe 300 having a feed pipe flange 310 at its end. In the end section of the feed pipe 300, there may be provided the safety device as disclosed in non-prepublished patent application PCT/NO2015/050158, but this is not essential. The combination of the two inventions, however, give extremely good results in terms of water hammer reduction. On the feed pipe flange 310 there is mounted the firewater monitor 200. The firewater monitor 200 comprises the nozzle 100 according to the invention, albeit a bit schematically illustrated.

Fig. 8 shows the firewater monitor 200 of Fig. 7 in a little bit more detail. The firewater monitor comprises a fixing flange arrangement 205 for enabling mounting on the feed pipe flange 310. Right above the fixing flange arrangement 205 there is visible a first swivel joint 220-1 forming part of a firewater monitor body 210 for allowing horizontal rotation of the firewater monitor 200. The firewater monitor body 210 comprises a piping, which is the inlet piping 212 referred to in the claims. The inlet piping 212 has an inlet flow area 212fa as illustrated, to which the outlet flow area is adapted as described earlier. The firewater monitor 200 also comprises a second, differently designed, swivel joint 220-2 for allowing vertical rotation of the firewater monitor 200. The first swivel joint 220-1 and the second swivel joint 220-2 form a joint assembly 220.

As is discussed in the description of the figures above, the invention aims to reduce water hammer or water surge in the nozzle of a firewater monitor. This effect is achieved by gradually throttling the outlet flow area of the nozzle. Even though the examples given in this description make use of the water pressure itself to throttle the flowing area, it must be noted that there are other ways as well. For instance, it is possible to have a throttling system, which is purely triggered by a time defined instant, i.e. the throttling is started right after or a little bit after that the nozzle in taken into operational use. Furthermore, the force needed for the actual throttling may be taken from other sources than then water pressure itself, for instance, an electric motor, a hydraulic motor, etc.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware.