US3903968A

US3903968A - Mixing apparatus

Info

Publication number: US3903968A
Application number: US450759A
Authority: US
Inventors: William L Livingston
Original assignee: Factory Mutual Research Corp
Current assignee: Factory Mutual Research Corp
Priority date: 1973-05-16
Filing date: 1974-03-13
Publication date: 1975-09-09
Anticipated expiration: 1992-09-09

Abstract

An injection apparatus for introducing a slurry of water swellable gelling agent into a water line feeding a fixed fire extinguishing system to form an ablative extinguishant therein. The apparatus includes a peristaltic pump driven by a hydraulic motor using water at line pressure for motive fluid and controlled by a servomechanism driven in part by a flow sensor to ensure injection rates corresponding to flow rates of water in the line. The injection apparatus is operated in a no-injection failure mode to avoid interference with normal flow of plain water to the fire extinguishing system.

Description

United States Patent Livingston Sept. 9, 1975 [5 MIXING APPARATUS 3,341,128 ii/I967 Nagin et al. 239/304 X 3,499,606 3/I97O Smith 239/304 [75] Inventor n' Sharon 3,559,890 2/1971 Brooks et al 239/304 ass.

[73] Assignee: Factory Mutual Research Primary ExaminerM. Henson Wood, Jr.

Corporation, Norwood, Mass. Assistant Examiner-Michael Mar Filed: Mar. I974 g ttorney, Agent, or Firm-Lane, Aitken, Dunner &

lems [2|] Appl. No.: 450,759

Related US. Application Data Division of Ser No. 360,963, May 16, 1973, Pat. No. 3,831,617, which is a continuation of Ser, No. 194,994, Nov. 2, 1971, abandoned, which is a division of Seri No. 864,757, Oct. 8, [969, Pat. No. 3,642,072.

[ 5 7 ABSTRACT An injection apparatus for introducing a slurry of water swellable gelling agent into a water line feeding a fixed fire extinguishing system to form an ablative extinguishant therein. The apparatus includes a peri staltic pump driven by a hydraulic motor using water at line pressure for motive fluid and controlled by a servomechanism driven in part by a flow sensor to ensure injection rates corresponding to flow rates of water in the line. The injection apparatus is operated in a no-injection failure mode to avoid interference with normal flow of plain water to the fire extinguishing system.

7 Claims, 5 Drawing Figures MIXING APPARATUS CROSS-REFERENCE TO RELATED APPLICATION This is a division of application Ser. No. 360,963 filed May 16, 1973 now U.S. Pat. No. 3,831,617, which, in turn, is a continuation of application Ser. No. 194,994, filed Nov. 2, 1971, now abandoned which, in turn, is a divisional of application Ser. No, 864,757 filed Oct. 8, 1969 now U.S. Pat. No. 3,642,072.

BACKGROUND OF THE INVENTION This invention relates to an additive injection system and more particularly, it concerns a system for injecting a gelling additive automatically into a water line to provide a fire extinguishant in the form of an ablative gel for supply to thermally actuated sprinkler heads in a fixed fire protection system.

In a copending application entitled Method of Controlling Fire," Ser. No. 766,475, filed Oct. 10, 1968 by William L. Livingston and Russell W. Pierce and assigned to the assignee of the present invention, a method of fire protection is disclosed in which a gelling agent in the form of a water swellable polymer is injected into a flowing stream of water supplying the sprinkler heads of a fixed extinguishing system upon actuation thereof to put out a fire in the enclosure protected by the system. By so introducing the gel into the flowing water stream, an ablative gel extinguishant is formed having certain advantages over plain water. Not only is the thermal absorption characteristics of the ablative gel greater than water, but equally as important, the gel is substantially more viscous than plain water and tends to cling to the surfaces on which it is sprayed. As a result, a much lower quantity of ablative extinguishant is required to put out a fire than that of plain water, thereby enabling system designs with lower flow capacity, not to mention a significant reduction in water damage to the space protected.

Although systems employing an ablative gel extinguishant, formed by introducing the polymer additive to a water main supplying sprinkler heads, have been found to be extremely effective in experimentation with actual fires, several problems have been presented in the development of a commercially acceptable system. For example, fixed fire extinguishing systems, in general, remain inactive for long periods of time, often exceeding several years duration. Under such circumstances, conventional items of fluid handling hardware can and most likely will become deteriorated due to corrosion and the like, presenting the possibility of malfunction at the same time when the system is called on to extinguish a fire. Also, operation of the system cannot be predicated on conventional power sources such as electricity, because that the probability of the power supply will be cut out during the conditions existing during a fire, particularly large fires of the type in which excessive property damage is likely to occur upon malfunction of the system.

The very nature of the swellable polymer gel additive, both in itselfbefore injection and its behavior after injection in a flowing stream of water, pose further serious problems to the design of an acceptable injection system. Perhaps the most serious of these problems arises out of the possibility of over injection. In this context, experimentation with ablative gel additives has demonstrated that optimum injection rates, from the standpoint of developing an ablative fluid which will readily flow through the system plumbing while at the same time maintaining the desired level of extinguishing capabilities, is approximately one to four parts gelling agent per thousand parts of water by weight. lnjec tion at higher rates than that indicated can and is very likely to create stoppages in the plumbing system. Obviously, such stoppages not only preclude the attainment of the desirable characteristics of the ablative fluid, but more significantly, disable the system to the extent that even plain water is prevented from reaching the sprinkler heads opened as a result of fire temperatures. The development of improved additive slurries has contributed greatly to solving the problems of handling polymer gel additives in fixed fire extingushing systems. Generally, such slurries involve mixing the gelling powder with a water soluble, thickened carrier which is chemically inert with the powder and which has a sufficiently high plastic flow yield value to suspend the polymer particles indefinitely. Yet, the avoidance of over injection remains important.

Another problem presented by the injection of additive gel slurries into a flowing stream of water is that of pumping and mixing the additive instantly and completely in the flowing stream. From the standpoint of pumping the slurries, a serious problem is presented by virtue of their dilatant characteristics, that is, their ten dency to increase in viscosity with corresponding increases in shear stress. Hence, conventional injection pumps which subject the slurry to high shear stresses cannot be used because of the tendency for the slurry viscosity to increase to a point where it becomes unpumpable. Also, it will be appreciated that the additive must be mixed uniformly in the flowing stream to avoid a localized gel build-up or the formation of globs likely to create stoppages in the same manner as that caused by over injection.

In light of the tolerances required of the various parameters of a gel additive injection system used with fixed extinguishing systems, and the need for the extinguishing system to be absolutely operative when called to extinguish a fire, it is also imperative that the additive injection system not impede the flow of plain water through the system. Hence, the injection system must be capable of achieving the characteristics outlined above without in any way presenting an obstruction in the conduit by which water is supplied to the sprinkler heads located in the building space protected.

SUMMARY OF THE INVENTION In accordance with the present invention, a gel slurry additive injection system is provided for fixed extinguishing systems by which substantially all of the problems heretofore experienced in the use of such additives are substantially avoided. More particularly, the injection system of this invention avoids the need for an external pumping power source by means of a hydraulic motor using as its motive fluid, water tapped at line pressure from the main conduit supplying the fire extinguishing system. Water is supplied to the motor through a control valve operated by a servomechanism in turn controlled by means responsive to water flow in the system feed conduit. The motor thus initiated and operated by water supplied to the fire extinguishing system is employed to drive an injection pump by which the additive gel slurry is introduced into the flowing line. Preferably, means in the form of an impact clutch is interposed between the motor and the pump so that the motor develops a sufficiently high torque after starting to drive the pump.

To overcome the problems arising as a result of the dilatant physical characteristics of the slurry, the pump employed in the injection system is preferably a peristaltic pump or one which develops a gradual build-up of pressure on the fluid being pumped, thereby avoiding an abnormal increase in the viscosity of the additive. Uniform mixing of the additive with the flowing stream of water is achieved with the injection system of the present invention by the employment of a baffle or eddy plate in the main water conduit at the point where the gel additive is introduced. It is preferred that the eddy plate be formed of material which is flexible so that under conditions where the gel is being introduced, thereby developing lower system flow rates due to the formation of the ablative fluid extinguishant in the system, the eddy plate functions to develop the necessary mixing flow paths and turbulence. Where however, the injection system fails upon the demand for extinguishant by the sprinkler heads in the fire extinguishing system, significantly greater flow rates are required by the system as a result of the relatively low viscosity of plain water. The eddy plate responds to these greater flow rates by flexing so that the increase flow rates needed by the sprinkler heads of the system are not impeded by the eddy plate.

Among the principal objects of the present invention are. therefore: the provision of a novel gel additive injection apparatus for fixed fire extinguishing systems by which the problems heretofore experienced are substantially overcome; the provision of such injection apparatus which is extremely reliable in operation, even though standing idle for long durations of time, to achieve a mixing of the additive with the flowing stream of water. thereby to develop an ablative extinguishant; the provision of an ablative gel injection apparatus of a type referred to which avoids over injection of the additive as well as measuring a uniform mixing of additive with water to avoid flow stoppages as a result of large globs of very viscous material in the flow line; and the provision of an injection apparatus of the type referred to which in no way impedes the flow of water to the sprinkler heads of the fire extinguishing system in the event of malfunction of the injection apparatus.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description that follows taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view illustrating the operative elements of the additive injections apparatus of the present invention in a fixed fire extinguishing system;

FIG. 2 is an enlarged fragmentary cross-section taken on line 2--2 of FIG. 1;

FIG. 3 is an enlarged cross-section taken on line 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross-section taken on line 4-4 of FIG. 3; and

FIG. 5 is a fragmentary cross-section similar to FIG. 4 but under different operating conditions of the injection apparatus and fire extinguishing system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings particularly in FIG. I

thereof, the injection apparatus of this invention is generally designated by the reference numeral 10 and is incorporated in a fire extinguishing system including a main feed conduit 12 connected by means of a T- coupling 14 to a riser 16. In accordance with conventional practice, the riser 16 extends upwardly to one or more branch lines 18 having a plurality of nozzles or sprinkler heads 20 depending therefrom. Also in accordance with conventional practice, each of the nozzles is provided with temperature responsive release means 21 so that upon the development of a fire in the vicinity of one or more of the nozzles, the system is activated automatically to supply water from the main conduit 12 through the riser 16, the branch line 18 and out of the nozzles 20.

Although the specific details of the injection apparatus 10 are not apparent from FIG. 1 and will be described in more detail below, the general organization of the apparatus is shown in FIG. 1 to include a storage tank 22 for a gel additive slurry preferably of the type described above.

The tank 22 is connected at its lower end by means of a discharge conduit 24 to the intake 26 of a peristaltic pump 28 having a discharge tube 30 coupled by a reducer 32 to the T-coupling 14. At the opposite end of the pump 28 from the tube 30 is a gear box and bearing assembly 34 for transmitting torque from an input shaft 36 in turn drivably connected to a hydraulic motor 38 by a motor output shaft 40 and slip-impact clutch 42.

The motor 38 is preferably of a positive displacement piston type designed to develop full torque at low speeds and has communication with the main conduit 12 by way of a tap line 46 having a control valve 48 therein. An exhaust pipe 50 is provided on the motor 38 so that the admission of water under line pressure to the intake port 44, through the pump 38 and out of the exhaust pipe 50 will effect rotation of the pump rotor (not shown) and correspondingly drive the output shaft 40 at speeds controlled by the valve 48 in a manner well known to those familiar with such pumps.

Because of the high reactive character of the contemplated additive when mixed with water to form a viscous gel capable of creating stoppages if over injection occurs, it is imperative that the rate of injection be controlled in a manner to avoid over injection and preferably by means having an under injection or no-injection failure mode. To this end, a servomechanism is provided to regulate the motor control valve 48 to insure that the pump 28 will be operated in conformity to flow rates in the conduit 12. To this end, a flow responsive device in the form of a rotatable screw 52 is supported in the main conduit 12. Rotation of the screw 52 is transmitted by means including a shaft 54 to one end input of a conventional differential gear 56 having output ring gear 58. The shaft 54 providing the input at one end of the differential gear 56 is connected to the sensing screw 52 by one-way torque transmitting means, such as a clutch 60, so that the shaft 54 may be rotated by the screw 52 but so that rotation of the screw by the shaft 54 is prevented. The other end of the differential 56 is connected by a servo-shaft 62 to a similar one-way torque transmitting device 64 on the motor 38. Because of this arrangement, the ring gear 58 will be driven in accordance with differential input from both ends by the

shafts

54 and 62. The ring gear 58 is in mesh with a gear 66 keyed to an actuating and control shaft 68 connected at its opposite end with the valve 48. Hence, with the shaft 62 stationary, rotation of the screw 52 as a result of water flow through the main conduit 12 will effect rotation of the shaft 54 to develop a differential output rotation of the ring gear 58. The ring gear 58 in turn rotates the gear 66 and shaft 68 to open the valve 48. At this point, it is to be noted that the valve 48 is preferably of the type having an inherent bias toward the open position to bring about an opening movement with a minimum of torque delivered to the shaft 68.

It will also be appreciated that in light of the differential being connected at the end thereof, opposite from the screw driven shaft 54, to the servoshaft 62, coupled to the motor 38, speed regulation of the motor 38 may be provided. Specifically, when the servo shaft 62 rotates faster than the shaft 54, the output ring gear 58 and correspondingly the gear 66 and control shaft 68 will be driven in a direction to close the valve 48 and slow down the pump to rotational speeds correlated directly to that of the screw 52. Inasmuch as the screw 52 is rotated at a rate corresponding directly to the flow rate of water through the main conduit 12, it becomes apparent that the motor 38 is regulated to operate at speeds corresponding to the flow rate of water through the pipe 12. correspondingly, the pump 28 which is driven by the motor 38 will be regulated to insure the proper agent-water ratio in the riser 16.

I The peristaltic pump 28, as above-mentioned, is available commercially and is known to be a positive displacement, progressive cavity-type. Such pumps, as shown in FIG. 2 of the drawings, include a worm-like rotor 70 disposed within a stator 72 which cooperates with the rotor upon rotation thereof to establish a series of progressively developed, discrete chambers advancing from the feed chamber 26 through the discharge tube 30. Also, as shown, the tube 30 extends through the T-coupling 14 in the embodiment shown and terminates at its open end 74 within the lower horizontal portion of the riser l6. Peristaltic pumps of this design are particularly suited for use in the injection apparatus of this invention because of their peristaltic action (Le, a gradual build-up of pumping pressure) in light of the dilatant physical characteristics of the gel additive slurry, and also because they function as a valve and will not pass fluid as long as the rotor 70 is stationary. While this latter characteristic, in itself, would prevent inadvertent discharge of the additive into the riser 16, it is contemplated that a frangible cap 76 is provided over the open end 74 of the pump to provide a positive seal between the additive and water within the line. The cap 76 is equipped with an explosive actuator 78 connected by a conductor 80 to a pulse generator 82 mechanically coupled to the output shaft 40 of the motor 38. Hence, rotation of the shaft 40 upon initiation of the system will operate the generator to deliver an electric pulse to the explosive 78 and quickly disintegrate the cap 76. To avoid occurrence of this function as a result of slight movements in the shaft 40 that may be brought about by minor pressure fluctuations in the water line 12, a capacitor 84 may be placed in the line 80 to store small electrical charges accumulated as a result of such slight rotation of the shaft 36. The capacitor 84 is selected, on the other hand, so that upon any continuous operation of the shaft 40, the capacitor will discharge to explode the charge 78 and disintegrate the seal cap 76.

In accordance with an important feature of the present invention, a mixing means in the form of an eddy plate 86 is provided at the open or discharge end of the tube 30 at the point where the gel additive is introduced into the horizontal portion of the riser 16. In this context it should be borne in mind that the characteristics of the gel additive are such that upon contact with water, the gel particles thereof immediately swell to form a relatively viscous fluid. Hence, in the event the additive is not thoroughly mixed with the water to which it is injected, there is a likelihood that large globs of gelatin will be formed, capable of developing flow stoppages in the riser 16, the branch line 18, or in the sprinkler heads 20 and resulting in a malfunction of the fire extinguishing system. Also, it is to be noted that the flow rate in the extinguishing system, when handling the ablative gel formed by the injection of the gel additive is significantly lower than it would be where plain water is used. Yet, because of the requirement for plain water to be delivered to the sprinkler heads 20 at sufficient rates to extinguish the fire in the event the injection apparatus malfunctions, it is imperative that both flow rates be accommodated.

With the aforementioned design requirements in mind, the eddy plate 86 is in the form of a circular disc and is fixed at the open end of the tube 30 by appropri ate means such as collars 88. The eddy plate 86 is formed of reasonably stiff rubber or other elastomeric materials having resilient, yieldable qualities so that at flow rates of the type that exist when ablative fluid is being fed to the sprinkler heads 20, it maintains a position normal to the pump discharge tube 30 as shown in FIGS. 3 and 4 of the drawings. In this position, the eddy plate 86 operates to create a zone of turbulence in the water as depicted in the solid line arrows in FIG. 4 of the drawings. Inasmuch as the pump 28 will be operative under these conditions to inject the gel additive out of the discharge end 74 thereof, the additive will pass into the turbulent zone as depicted by the dash line arrows in FIG. 4 and be uniformly and thoroughly mixed with the water to provide the desired viscosity of the ablative extinguishant delivered to the sprinkler heads 20. If, on the other hand, the injection apparatus 10 should malfunction so that the ablative extinguishant is not formed, the fire extinguishing system plumbing including the riser l6, branch line 18, and sprinkler heads 20 will permit flow at significantly higher rates. Although the eddy plate, if rigid, would present an obstacle to such high flow rates between the main conduit 12 and the riser 16, being formed of flexible material, it will partially collapse to the position illustrated in FIG. 5 of the drawings and permit water to flow at high rates into the riser l6.

Summarizing the operation of the injection apparatus 10, it will be apparent that upon opening any one of the sprinkler heads 20, water will pass through the main conduit 12, rotating the screw 52 and effect opening of the valve 48 by way of the differential 56 as described. Thereupon, the motor 38 will be operated to rotate the shaft 40 and immediately operate the generator 82 to deliver an electric pulse through the capacitor 84 to the explosive 78 and disintegrate the sealing cap 76 on the open discharge end of the pump 28. As soon as the motor 38 has developed its operating output torque, the shaft 40 will be coupled with the drive shaft 36 of the pump 28 by way of the slip-impact clutch 42 to initiate rotation of the pump rotor 70. The gel additive slurry, which is passed by gravity from the tank 22 through the discharge pipe 24 into the pump feed chamber 26, will be pumped through the tube 30 and out through the open end 74 thereof to be mixed with the flowing stream of water in the turbulent zone immediately downstream from the eddy plate 86 in the manner described above. The danger of over injection of the additive to the system is avoided by virtue of the fact that the motor uses as its motive fluid, water in the feed line 12 and also because of the under-inject failure mode of the injection apparatus. In other words, should any component of the injection apparatus malfunction, the result will be under injection or no injection, in which case the eddy plate would flex out of the way as described above to permit an adequate supply of water to reach the sprinkler heads to be effective in extinguishing the fire.

Thus it will be appreciated that by this invention there is provided a highly effective and unique injection apparatus particularly suited for use with fire extinguishing systems of the type described and by which the above-mentioned objectives are completely fulfilled. Also, it is contemplated that numerous variations may be made in the injection apparatus depicted by the disclosed embodiment, which variations fall within the true spirit and scope of the present invention.

1 claim:

1. An apparatus for forming a composition at least one of the components of which is flowable, said apparatus comprising means defining a mixing area for said components, a conduit associated with each component for delivering said components from their respective sources to said mixing area, at least a portion of the conduit for delivering said flowable component enclosing at least a portion of the conduit for delivering another component to define an annular flow channel for said flowable component between said conduits, and an annular member extending in a portion of said annular flow channel in a manner to interfere with the flow of said flowable component through said flow channel to impart a turbulence to said flowable component, said annular member being adapted to vary said interference in response to changes in the flow rate of said flowable component.

2. The apparatus of claim 1 wherein said flowable component is water and wherein another component is a slurry.

3. The apparatus of claim 1 wherein said annular member is of a resilient material and is adapted to collapse in response to increases in said flow rate to vary said interference.

4. An apparatus for forming a composition of two components at least one of which is flowable, said apparatus defining a first conduit means connected at one end to a source of one of said components, second conduit means connected at one end to a source of the other component, said second conduit means extending within said first conduit means in a coaxial relationship to define an annular flow channel for said one component, the other end of said second conduit means terminating within said first conduit means to define a mixing area for said components in said first conduit means adjacent said other end of said second conduit means, and an annular member extending in a portion of said annular flow channel in a manner to interfere with the flow of said one component through said flow channel for imparting a turbulence to said one component, said annular member being adapted to vary said interference in response to changes in the flow rate of said one component.

5. The apparatus of claim 4 wherein said one component is water and wherein said other component is a slurry.

6. The apparatus of claim 4 wherein said annular member is of a resilient material and is adapted to collapse in response to increases in said flow rate to vary said interference.

7. An apparatus for forming a composition of two components at least one of which is flowable, said apparatus defining a first conduit means connected at one end to a source of one of said components, second conduit means connected at one end to a source of the other component, said second conduit means extending within said first conduit means in a coaxial relationship to define an annular flow channel for said one component, the other end of said second conduit means terminating within said first conduit means to define a mixing area for said components in said first conduit means adjacent said other end of said second conduit means, and means extending in a portion of said annular flow channel for imparting a turbulence to said one component and for varying said turbulence in response to changes in the flow rate of said one component.