AU6584394A

AU6584394A - A foam proportioner

Info

Publication number: AU6584394A
Application number: AU65843/94A
Authority: AU
Inventors: Gary Trevor Love
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-05-06
Filing date: 1994-05-06
Publication date: 1994-12-12
Also published as: WO1994026353A1

Description

A FOAM PROPORTIONER

This invention relates to a foam proportioner and more particularly to a mechanism for mixing foam and water to be used as a fire suppressant.

Foam is 3 to 5 times more effective as a fire suppressant than water alone. This is because foam both smothers and cools the fire, hence removing both the oxygen and heat required to create and sustain fire. Conversely, water only cools the fire. Foam is also safer to use in fires where electricity and/or oil is involved. At present fire fighting foam is produced in a number of ways and one of these is a batch mixing process. Concentrate wastage from batch mixing is a problem with existing processes as is tank and pump corrosion.

An object of the invention is to overcome the above- identified disadvantages and to offer users a useful alternative choice.

Further objects and advantages of the invention will become apparent from the following description which is given by way of example only.

According to a broadest aspect of this invention there is provided a proportioner mechanism including a water flow sensor, a concentrate metering valve, a concentrate pressure regulator, a concentrate booster pump, the arrangement being such that the rate of flow of concentrate, which is at atmospheric pressure, from a supply tank is powered by pressure from a liquid supply which is automatically pressure adjusted by a pressure regulator to adjust the flow rate of concentrate to be mixed.

The proportioner mechanism can be used to mix a foam concentrate with water for use in a fire fighting situation.

According to a second aspect of the invention there is provided a foam proportioner in which the flow rate through a metering valve is continuously monitored to control the injection rate of a foam concentrate, the proportioner incorporating a foam concentrate pressure regulator the operation of which is solely controlled by water pressure which is varied in accordance with variations in pressure in a foam pressure sense line and a water reference pressure line.

According to an alternative aspect of the invention there is provided a foam proportioner suitable for a fire tender, the proportioner including a pump, venturi, dual differential regulator controller, metering valve, regulator, the arrangement being such that water from a tank is drawn by the pump and directed to the venturi from which mixed foam and water is delivered, the foam being proportioned after being drawn from a foam tank through the regulator to the metering valve from which the concentrate passes to a venturi which surrounds the pump, the volume of foam being controlled by the dual differential regulator controller, controlled from the venturi to the regulator.

Further aspects and advantages of the invention will become apparent from the following description.

Examples of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 shows a block diagram of the parts of a foam proportioner according to the invention;

Figure 2 shows a schematic circuit diagram of a control system for controlling the foam proportioner shown in Figure 1;

Figure 3 shows a section through a booster pump for the foam proportioner shown in Figures 1 and 2; and

Figure 4 shows a block diagram of the parts of an alternative construction of foam proportioner according to the invention.

Examples of the invention will be described with reference to a foam proportioner for use in producing fire fighting foam. It is to be appreciated that the invention can be used in other situations for mixing liquid concentrate and a liquid.

In the first example as is shown in Figure 1 the proportioner has a delivery flow sensor 1, a foam concentrate booster pump 2, a foam concentrate pressure regulator 3 and a foam concentrate metering valve 4. The foam concentrate from tank 5 (not shown in Figure 1) flows in the direction of the arrow to the booster pump 2. The output from the booster pump 2 passes through the pressure regulator 3. The pressure at the regulator 3 is sensed by the delivery flow sensor 1. The output from the regulator 3 passes to the foam concentrate metering valve 4 from which the foam concentrate passes to a venturi mixer 6 associated with a water flow.

In the schematic diagram in Figure 2 is shown, a control mechanism for the proportioner. The control mechanism utilises the pressure of the water supply to fully control the operation of the proportioner. In Figure 2 similar parts to those shown in Figure 1 are indicated by the same numerals.

The control mechanism includes a sense change over valve 7, a pair of power changeover valves 8, 8', a water ram 9, a foam concentrate ram 10 and a pressure compensation piston 11. The valve 8' is slave off valve 8. The mechanism is configured as shown.

In use the delivery flow sensor 4 has a diaphragm 12 one side of which is connected to the water reference pressure line at 14. The other side of the diaphragm 12 is connected to a foam pressure sensor line 15. Movement of the diaphragm 12 via piston 16 controls the flow of foam at 17 to the venturi at A. An advantage of the invention is that the proportioner maintains the ratio of concentrated (foam) liquid at a preset value no matter what pressure or flow rate exists in the liquid to which the concentrate is being mixed.

Pump cavitation and priming is overcome by injecting the concentrate after the pump. The difficulties and problem of educators are prevented by injecting the concentrate at the delivery pressure.

In Figure 3 is shown a section through a booster pump which can be used in the proportioner shown in Figures 1 and 2. The booster pump is an integrally formed unit and is indicated generally by the arrow 2. The booster pump 2 is powered by water pressure and can replace the water ram 9 and foam ram 10 shown in Figure 2.

The booster pump 2 has a casing 18 and body 19 formed or fabricated to support therein a reciprocating piston 20. The piston 20 when operating boosts the pressure in a foam passing from a suction end or inlet 21 to outlet 22.

The piston 20 has a bore 23 therethrough which is sealed by 0-ring seals 24 which contact the surface of spigot 25 which is formed as part of the body 19. The bore 23 has at one end a non-return or check valve 26 which is mounted with associated springs etc. in the chamber 28. The movement of the piston 20 is governed by stops 29 and 34. The piston 20 is dimensioned at its outer surface 31 to move in a bore 32 in the body 19. The surface 31 has 0- ring seals 33 which seal against the inner surface of the bore 32. The volume 30 of the bore 32 is selected so that the piston 20's movement results in a double action pumping effect.

The suction or inlet end 21 of the body 19 has a non¬ return valve 27.

The body 19 has valve surfaces 35, 36 on which power valve sleeve 37 and sensing valve sleeve 38 slide respectively.

The inner surface of the sensing valve sleeve 38 contacts a surface 40 on the periphery of the piston 19. The outer surface 41 of the sleeve 38 has rebates 42, 43, 44, 45 and 46 in its surface. The outer surface 41 at end 47 contacts the inner surface 48 of the casing 18. The surface 41 has the rebates 44, 45 and 46.

The inner surface 49 of the power valve sleeve 37 contacts the outer surface 50.

An outer surface 51 contacts a rebated section 52 on the inner surface of the casing 18 in which section 52 the sleeve 37 reciprocates in the directions shown. The outer surface of the sleeve 37 has circumferential grooves 53 between which are abstracts with 0-ring seals 54. The casing 18 has in its surface a series of ports.

The port 55 is connected to the power valve drive. The ports 56 are exhaust ports. The ports 57 and 58 are connected and act as pilot port A and B respectively. The port 59 is connected to act as a piston position sense valve drive. The ports 60 are exhaust ports. The ports 61 and 62 are connected to ports 57 and 58 respectively.

The sensing valve sleeve 39 has passages 63, 64 which are positioned to communicate with chamber 65, 66 formed between the body 19, pump piston 20 and sleeve 38.

The power valve sleeve has passages or galleries 67, 68 and 69. In use the booster pump 2 increases the pressure in the foam flow when the pump piston 20 is reciprocating in the direction of arrows 70. The non¬ return valves 26 and 27 operating successively to ensure there is no back flow in a direction opposite the foam flow 71. Operation of the piston 20 is regulated through the movement of the power valve sleeve 37 which is moved by the piston 20 when it successively contacts the abutments 29 and 34. Movement of the power valve sleeve 38 is controller by the sensing valve sleeve 38. The 5-ports or passages of the sense valve sleeve 38 slave the water pressure to move the power valve sleeve 37. According to the sensed positions pressure is applied to chambers 65 and 66 from the power valve drive inlet 55 to thereby move the piston 20. The position of the power valve sleeve 37 is controlled by inputs from the pilot control ports (A) 61 and (B) 62 via ports 57 and 58 respectively to vary the flow from the power valve drive port 55 to reciprocate the piston 20.

Typical specifications of an example of the invention are: Maximum foam concentrate pumping rate 12 litres/min

Maximum operating pressure 2400 KPA

Minimum operating pressure 100 KPA

Metering valve 12 position rotary

Standard proportioning ratio range .05% - 1%

Maximum recommended flow rate 2400 litres/min at 1200 KPA

Insertion pressure loss at designed flow rate of 1200 litres/min at 15 KPA

Tank capacity 60 litres Optional extra flow meter for use with compressed air foam system

The flow of foam concentrate is controlled through the mechanism shown in Figure 2 where high pressure water is used as the means to control the concentrate flow.

Figure 4 shows a block diagram of the parts of an alternative construction of foam proportioner. In this construction a fully propor^tioned and accurate supply of foam is supplied over a full range of water flows. This has not been possible with existing equipment. This added control is given by a dual differential regulator controller 72. A pump 73 in this example draws water from a water tank at 74 and it flows in the direction indicated to a venturi 75 from which a delivery of between 0 - 6000 litres/min is obtainable.

Foam from a tank at 76 is supplied via a regulator 77, through a metering valve 78 to a round the pump venturi 79. The volume of foam inducted into the venturi 79 is between 0 - 480 litres/min and this is directed at connection 80 prior to the pump 73.

The regulator 77 is controlled by an output from the dual differential regulator controller 72 which senses throughput before and after the metering valve 78 and at two points in the venturi 75.

The control thereby supplied from controller 72 is over the full range of flows through the system. The proportioner adds foam of between 0 - 8% at 6000 litres per minute.

Another advantage is that the mechanism is a self- contained high pressure foam concentrate to water proportioner powered by water pressure. The proportioning is continuous with the concentrate tanks remaining at atmospheric pressure.

Thus by this invention there is provided a mechanism for mixing foam and water to be used as a fire suppressant.

A particular example of the invention has been described and it is envisaged that improvements and modifications can take place without departing from the scope thereof.

Claims

1. A foam proportioner which includes a water flow sensor, a concentrate metering valve, a concentrate pressure regulator, a concentrate booster pump. The arrangement being such that the rate of flow of concentrate from a supply tank is determined by pressure from a liquid supply.

2. A proportioner as claimed in claim 1 wherein a pressure regulator determines the pressure of the liquid supply.

3. A proportioner as claimed in claim 1 or 2 wherein the concentrate is at atmospheric pressure.

4. A proportioner mechanism as claimed in any one of the preceding claims wherein the proportioner mechanism is used to mix a foam concentrate with water for use in a fire fighting situation.

5. A proportioner in which the flow rate through a metering valve is substantially continuously monitored to control the injection rate of a concentrate, the proportioner incorporating a concentrate pressure regulator, the operation of which is solely controlled by water pressure which is varied in accordance with variations in pressure in a concentrate pressure sense line and a water reference pressure line.

6. A proportioner as claimed in claim 5 wherein the booster pump is manufactured in accordance with Figure 3 of the accompanying drawings.

7. A foam proportioner suitable for a fire tender, the proportioner including a pump, venturi, dual differential regulator controller, metering valve, regulator, the arrangement being such that water from a tank is drawn by the pump and directed to the venturi from which mixed foam and water is delivered, the foam being proportioned after being drawn from a foam tank through the regulator to the metering valve from which the concentrate passes to a venturi which surrounds the pump, the volume of foam being controlled by the dual differential regulator controller, controlled from the venturi to the regulator.

8. A foam proportioner mechanism substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

9. A foam proportioner as herein described with reference to Figure 4 of the accompanying drawings.