GB2289229A

GB2289229A - Mixing device for fire-fighting foaming agent uses double venturi

Info

Publication number: GB2289229A
Application number: GB9508670A
Authority: GB
Inventors: Hermann Goehringer
Original assignee: Total Walther Feuerschutz GmbH; Total Feuerschutz GmbH
Current assignee: Total Walther Feuerschutz GmbH; Total Feuerschutz GmbH
Priority date: 1994-05-04
Filing date: 1995-04-28
Publication date: 1995-11-15
Anticipated expiration: 2015-04-28
Also published as: NO951626D0; DE4415709A1; FR2719501B1; FR2719501A1; GB2289229B; NL1000262C2; NO951626L; SE9501423L; GB9508670D0; SE9501423D0; DE4415709C2

Description

--11 ADMIXING DEVICE FOR POAMING AGENTS 2289229 The invention relates to

an admixing device for foaming agents, wetting agents or the like for fireextinguishing devices in stationary or mobile installations or in fire-fighting vehicles. More particularly, it relates to an admixing device comprising a venturi, which has means of connection, e.g. a flange connection, on either side for installation into an extinguishing agent line, and an additive regulator with a restriction point in the additive supply line.

Such devices are used in fire-extinguishing installations for admixing a foaming agent to the firefighting water. To said end, the admixing device is controlled in such a way that an identical percentage admixture of foaming agent is always supplied to the fire-fighting water even with a fluctuating flow rate. The flow range in the known admixing devices, in which the admixing rate is constant, is 1: 7. This is a very narrow range, so that with the conventional admixing devices only very few eventualities may be covered.

There is therefore a need for an automatic admixing device in a housing having a flow range of 1 50 with a simultaneous, sufficient dosing capacity which is constant over the entire flow range.

According to the present invention there is provided an admixing device for foaming agents, wetting agents or the like for fireextinguishing devices in stationary or mobile installations or in firefighting vehicles, which device comprises a venturi, which has means of connection on either side so as to enable it to be installed into an extinguishing agent line, and an additive regulator and an additive supply line with a restriction point in the additive supply line, wherein the venturi, so as to form an annular channel, comprises an outer venturi nozzle and an inner venturi tube, with which there is associated at the outlet end a spring-loaded butterfly valve which covers the annular channel, and wherein the additive supply line is provided with a check or non-return valve, and that branching off from the additive supply line upstream of the restriction point is a bypass line also having a restriction point, which opens out into a mixing chamber downstream of the venturi.

The admixing device according to the present invention is provided with a double venturi and two separate supply lines for the additive, both lines being provided with a restriction point. By means of the spring-loaded butterfly valve either the inner or the inner and the outer venturi are opened as a function of the flow rate. The non-return valve in conjunction with the regulator regulates either the one or both foaming agent supply lines as a function of the flow rate of fire-fighting water.

With said admixing device, given a low flow rate of fire-fighting water, foaming agent is admixed only through the smaller, inner venturi tube because the annular chamber of the outer venturi nozzle remains closed. During said process, the non-return valve closes so that no water may flow through the first restriction point to the second restriction point. It is thereby ensured that, when the flow rate is low, foaming agent is admixed only through the second restriction point.

When the flow rate is high, the spring-loaded butterfly valve, which closes the outer venturi nozzle, opens and clears said nozzle. At the same time, the non-return valve opens and thereby enables admixture also through the first restriction point.

The restriction points, which may be metering or proportioning valves, restrictrs, chokes, throttles 1-111 or the like, are adjusted once to a specific flow rate. In connection with the regulator, water and foaming agent are under identical pressure. Upon a variation of the differential pressure in the venturi, the quantity of foaming agent automatically alters so that the desired quantity of foaming agent to be admixed is adjusted as a function of the pressure difference.

So that the admixture of foaming agent remains constant over the entire flow range, it is further proposed that the ratio of the diameter of the inner venturi tube to the diameter of the outer venturi nozzle is in the cross-sectional ratio between 1 and 1: 10, preferably being 1: 7.

3 It is further proposed that the ratio of the diameter of the supply line to the diameter of the outer venturi nozzle is in the ratio between 4: 1 and 2: 1, preferably being 3: 1.

An embodiment of the invention is illustrated in the drawing and described in greater detail hereinafter.

The admixing device 1 comprises the following individual parts. A regulator 3 is connected to a connection piece 2 for connection to an additive feed line (not shown). Emanating from the regulator 3 is a supply line 5, in which a restriction point 6 is disposed. Said restriction point may comprise a metering or proportioning valve, a restrictor,choke, throttle or some other suitable device. Downstream of the restriction point 6, a check or non-return valve 7 with a flap trap or non-return flap 8 and a spring 9 is provided. The supply line 5 opens via an inflow or feed opening 17 into a double venturi 12. Branching off upstream of the restriction point 6 and in the region of the supply line Sa is a bypass line 10 which is provided with a second restriction point 11. Said restriction point may likewise comprise a metering or proportioning valve, a restrictor, choke, throttle or some other suitable device. With the pipeline portion 10a and an inflow or feed opening 25, the bypass line 10 opens into a mixing chamber 22. The double venturi 12 is provided at the inlet side with a supply connection piece 23 and at the outlet side with a discharge connection piece 24. The connection piece 23 is connected by means of a flange 26 to a fire-fighting water line (not shown). The discharge connection piece 24 is connected by means of a flange 27 to a water foaming agent line (not shown). The double venturi 12 comprises an outer venturi nozzle 13 with a diffuser 14 and an inner venturi tube 18. The venturi nozzle 13 has a plurality of inlet openings 15. The outer venturi nozzle 13 and the inner venturi tube 18 form an annular channel 19 which, at the end of the diffuser 14, forms an annular diffuser outlet opening 16. The latter is closable by means of a butterfly valve 20 which is loaded by means of a spring 21. Provided on the butterfly valve 20 in extension of the inner venturi tube 18 is a diffuser 31 with inlet openings 32. 28 denotes the diameter of the supply connection piece 23, 29 the diameter of the venturi nozzle 13 and 30 the diameter of the venturi tube 18. The regulator 3 is connected by a control line 4 to the supply connection piece 23.

The admixing device according to the invention operates as follows.

The regulator 3 regulates the pressure of the foaming agent in the area d in accordance with the pressure b in the connection piece 23. Said regulation and the rate of feed of fire- fighting water into the connection piece 23 causes the adjustment in the annular chamber 19 of a pressure a, which is transmitted through the non-return valve and corresponds to the pressure c in the line 5. The fl 1 1 restriction point 6 is adjusted once to a specific flow rate. If the underlying flow rate of fire-fighting water varies, the differential pressure automatically alters. The restriction point 11 is likewise adjusted once to a specific flow rate. As a result, a pressure f appears or is felt in the line 10a. Inside the venturi tube 18, a pressure e sets in. The spring force 21 is so adjusted that the butterfly valve 20 holds the annular channel 19 closed up to a specific pressure. This means that, given a low flow rate of fire-fighting water, the force exerted thereby upon the inside of the butterfly valve is not sufficient to lift said valve and hence open the annular channel in relation to the mixing chamber 22. The spring force of the spring 9 is moreover adjusted in such a way that said spring keeps the passage for the additive closed by means of the nonreturn flap 8. Fire-fighting water is thereby prevented from flowing back through the two restriction points 6 and 11 into the mixing chamber. Given a low flow rate, the butterfly valve 20 and the non-return valve 7 therefore remain closed. Thus, the low quantity of fire-fighting water flows through the inner venturi tube 18 into the mixing chamber 22. The additive flows through the bypass line 10 with the restriction point 11 likewise into the mixing chamber 22, where fire- fighting water and foaming agent are mixed and discharged as a mixture through the connection piece 24. Upon an increase in the flow rate of fire-fighting water, the dynamic pressure upstream of the butterfly valve 20 also increases, as a result of which said valve is opened. The pressure in the annular channel 19 therefore alters so that at the same time, via the non-return valve 7, the same pressure sets in at c in the line 5. The additive then flows through the openings 15 into the annular channel 19 and flows together with the fire-fighting water into the mixing chamber 22. If the flow rate and hence the pressure upstream of the butterfly valve 20 is reduced, the spring 21 closes the annular channel 19 so that once more fire-fighting water is supplied only through the inner venturi tube 18 and the additive is admixed through the restriction point 11.

Claims

1. Admixing device for foaming agents, wetting agents or the like for fire-extinguishing devices in stationary or mobile installations or in fire-fighting vehicles, which device comprises a venturi, which has means of connection on either side so as to enable it to be installed into an extinguishing agent line, and an additive regulator and an additive supply line with a restriction point in the additive supply line, wherein the venturi, so as to form an annular channel, comprises an outer venturi nozzle and an inner venturi tube, with which there is associated at the outlet end a spring-loaded butterfly valve which covers the annular channel, and wherein the additive supply line is provided with a check or non-return valve, and that branching off from the additive supply line upstream of the restriction point is a bypass line also having a restriction point, which opens out into a mixing chamber downstream of the venturi.

2. Admixing device according to claim 1, wherein the ratio of the diameter of the inner venturi tube to the diameter of the outer venturi nozzle is in the cross-sectional ratio between 1: 3 and 1: 10.

3. Admixing device according to claim 2, wherein the ratio is approximately 1: 7.

4. Admixing device according to claim 1, wherein the ratio of the diameter of the supply line to the diameter of the outer venturi nozzle is in the ratio between 4: 1 and 2: 1.

5. Admixing device according to claim 4, wherein the ratio is approximately 3: 1.

6. Admixing device according to any one of claims 1 to 5, wherein the regulator via a control line keeps the pressure in the supply line and the pressure in the additive supply line and the bypass line equal.

7. Admixing device according to any one of claims 1 to 6, characterized in that the venturi nozzle is provided with a diffuser and the venturi tube is provided with a diffuser.

8. Admixing device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing 4 k