EP0084754A1 - Back flow preventer for hydraulic conduits - Google Patents

Abstract

Controlled by the membrane (3), the valve (18) opens the chamber drain (6) if the downstream flows back through (35). The spring (26) opens this drain, even if the membrane (3) is punctured.

Description

The present invention relates to a backflow preventer, intended to equip hydraulic pipes, the pollution of which is to be avoided. The liquid circulating in these pipes can be of all kinds. It can be water, and in particular drinking water or various liquids used in the chemical industry.

• lorsque le liquide circule dans la direction considérée comme normale, le disconnecteur laisse librement communiquer les circuits situés en amont et en aval ; si par contre le sens de circulation des liquides vient à s'inverser, le disconnecteur se ferme automatiquement et empêche le liquide du circuit aval considéré comme pollué, de remonter dans le circuit amont.

The principle of backflow preventers is as follows:

• when the liquid circulates in the direction considered to be normal, the backflow preventer freely communicates the circuits located upstream and downstream; if, on the other hand, the direction of circulation of the liquids is reversed, the backflow preventer closes automatically and prevents the liquid from the downstream circuit considered to be polluted, from going back into the upstream circuit.

Backflow preventers operating according to this principle are known. In the event of flow reversal, the backflow preventer protects the upstream circuit and discharges the liquid from the downstream circuit to the outside. This is used, for example, in the chemical industry for highly polluting waters: polluted water is prohibited from going up to the source of clean water, even if an ordinary valve, which has become defective, ceases to be waterproof. Furthermore, if the interior space of the backflow preventer defines a dead zone, it must be guaranteed that the water considered as polluted contained in this dead zone does not risk being sucked back towards the upstream circuit, that is to say towards the clean circuit:

Disconnection devices are known which make it possible to obtain certain results, but they have drawbacks.

Some are very complicated. Most present a risk because, if they perform their function well in normal times, their design does not allow them to ensure absolute security in certain cases. This can result in serious incidents.

The object of the present invention is to avoid these drawbacks by providing a backflow preventer in which any operational incident gives rise to a visible leak from the outside without, however, allowing any re-aspiration of the polluted downstream liquid.

Furthermore, the invention aims to produce a backflow preventer of simple construction, using only type valves and membranes. current.

A hydraulic backflow preventer according to the invention comprises a hollow body provided with an upstream connection end piece and a downstream connection end piece equipped respectively with an automatic valve with upstream spring and an automatic valve with downstream spring, while between the seats of these two valves are defined by an intermediate chamber at the lower part of which is a fixed seat for a discharge opening which opens towards the outside, this seat cooperating with a discharge valve situated at the part bottom of a vertical movable rod, the upper part of which is connected to a membrane surmounted by a pressure chamber which communicates directly with the upstream connection nozzle.

According to another characteristic of the invention, the vertical rod of the relief valve is hollow, its lower end being permanently open to the outside, while its upper end is capable of being closed off on an intermediate seat secured to the body .

According to another characteristic of the invention, a spring bearing on this intermediate seat and under a lower cup fixed to the membrane tends to move the relief valve and the upper end of the hollow rod away from their respective seats simultaneously.

According to another characteristic of the invention, the lower part of the intermediate cavity is formed of inclined blades so as to cause a vortex to appear within the liquid which increases the rate of emptying of this intermediate zone when the discharge valve s' open. This latter arrangement, combined with the effect of the air entering which occurs through the hollow rod, causes in an emergency extremely rapid emptying of the polluted liquids possibly contained in the intermediate cavity.

According to another characteristic of the invention, an upper cup secured to the membrane and the lower cup is capable of cooperating with a fixed seat in the upper part of the body, the central part of this seat communicating with the upstream pressure chamber.

• Figure 1 est une vue en coupe longitudinale d'un disconnecteur selon l'invention en position de repos.
• Figure 2 est une coupe analogue lorsque le disconnecteur est en position de fonctionnement normal.
• Figure 3 illustre le fonctionnement lors d'un incident possible, à savoir lorsque la membrane est crevée.
• Figure 4 est une coupe suivant IV-TV (figure 3%.

The appended drawing, given by way of nonlimiting example, will allow a better understanding of the characteristics of the invention.

• Figure 1 is a longitudinal sectional view of a backflow preventer according to the invention in the rest position.
• Figure 2 is a similar section when the backflow preventer is in the normal operating position.
• Figure 3 illustrates the operation during a possible incident, namely when the membrane is punctured.
• Figure 4 is a section along IV-TV (Figure 3%.

The backflow preventer illustrated in the drawings comprises a hollow body 1 capped with a cover 2, which closes it tightly. Between the hollow body 1 and the cover 2 are clamped the edges of a flexible waterproof membrane 3, the central part of which remains mobile.

The hollow body 1 is provided with an upstream connection nozzle 4 and a downstream connection nozzle 5.

• - de l'embout de raccordement 4 par un clapet automatique amont 7 formé d'un siège fixe 8 devant lequel un organe obturateur 9 peut coulisser sous l'action d'un ressort de rappel 10 ;
• - de l'embout de raccordement aval 5, par un clapet automatique aval 11 comprenant un siège annulaire fixe 12 devant lequel un organe obturateur 13 peut se déplacer sous la poussée d'un ressort de rappel 14.

In the center of the hollow body 1 is defined an intermediate chamber 6. This is separated:

• - the connection piece 4 by an automatic upstream valve 7 formed by a fixed seat 8 in front of which a shutter member 9 can slide under the action of a return spring 10;
• - the downstream connection nozzle 5, by an automatic downstream valve 11 comprising a fixed annular seat 12 in front of which a shutter member 13 can move under the thrust of a return spring 14.

As shown in the drawings, these two upstream 7 and downstream 11 valves are oriented in the same direction, that is to say that they both tend to open under the pressure of a fluid pressure when the liquid normally flows from the upstream nozzle 4 to the downstream nozzle 5, as shown diagrammatically in FIG. 2 by the arrows 15 and 16.

The intermediate chamber 6 defined between the seats 8 and 12 of the two aforementioned valves also opens outwards thanks to a fixed seat 17 located at its lower part.

This fixed discharge seat 17 cooperates with a discharge shutter 18 capable of sealing it. The shutter 18 is located at the lower part of a vertical movable rod 19, the upper part of which is connected to the central part of the membrane 3, by means which will now be described.

The vertical rod 19 of the discharge shutter is hollow: an axial bore 20 traverses it over its entire length so as to be permanently in communication with the external atmosphere, by its lower end passing through the center of the seat 17. The upper end of this rod forming a shutter 21 is capable of coming to cooperate with a seat 22 in the lower part of a chamber in communication with the axial bore 20.

The hollow rod is provided with radial arms 23 passing through the intermediate seat in order to be fixed on the lower cup 24 so as to secure the action of the membrane with the relief valve 18 and the shutter 21 of air intake.

The lower part of the intermediate cavity is formed of inclined blades 25 so as to cause a liquid vortex or vortex to appear within the liquid, increasing the rate of emptying of the liquid in this zone when the relief valve 17-18 is open.

On the upper face of the intermediate seat is supported a compression spring 26, the top of which bears under the lower cup 24. The action of this spring tends to lift the relief valve 18 above its seat, on the other hand to raise the shutter 21 above its seat 22.

Above the membrane an upper cup is fixed by a central hole to the membrane on the lower cup. The membrane 3 is thus clamped and shouldered between the cups 24 and 27. The upper cup is provided with an annular seal 28 capable of cooperating with a seat 29 located on the central part of the cover 2. A pressure chamber 30 is located thus defined in inside of the cover above the upper cup 27 on its seat 28. This pressure chamber communicates directly with the upstream connection nozzle 4 by a channel 31 which opens upstream of the valve 7.

The upstream pressure prevailing in the connection piece 4 is permanently applied in the chamber 30 whether the upstream valve 7 is open or closed. A second chamber 32 is also defined, still inside the cover 2, between the shutter 28 and the membrane 3.

The operation is as follows

When the backflow preventer according to the invention is not connected, that is to say when it is at rest, its organs occupy the positions illustrated in FIG. 1

• - le clapet amont 7 est fermé ainsi que le olapet aval 11 ;
• - le clapet de décharge 17 , 18 , 21 , est ouvert ;
• - l'action du ressort 26 maintient le joint 28 de la coupelle 27 appliqué de façon détanche sur le siège 29 .

In other words

• - the upstream valve 7 is closed as well as the downstream valve 11;
• - the discharge valve 17, 18, 21 is open;
• the action of the spring 26 maintains the seal 28 of the cup 27 applied in a sealed manner to the seat 29.

When the backflow preventer is connected between an upstream circuit connected to the nozzle 4 and a downstream circuit connected to the nozzle 5, it retains the rest position illustrated in FIG. 1 if the upstream pressure in the nozzle 4 and in the chamber 30 is insufficient to cause the closure of the shutter of the relief valves 17, 18, 21, 22.

• - dans un premier temps , les clapets 7 et 11 restant tous deux fermés , l'augmentation de pression dans la chambre 30 commence par abaisser la partie centrale de la membrane 3 , c'est à-dire le joint 28 décolle de son siège 29 ;
• - aussitôt , la pression amont se met à intéresser la totalité de la surface de la face supérieure de la membrane 3 dont la partie centrale s'abaisse alors rapidement en comprimant le reasort 26 , jusqu'à ce que l'obturateur 18 vienne s'appliquer de façon étanche sur son siège 17 , ainsi que le clapet 21 sur son siège 22 ; désormais , la chambre intermédiaire 6 ne com- minique plus avec l'extérieur ;
• - à ce moment , du fait du jeu des tarages des divers ressorts et du dimensionnement des surfaces intéressées par la pression, le clapet amont 7 s'ouvre et une pression inférieure à la pression amont 15 s'établit dans cla chambre intermédiaire 6 ;
• - une fois cette pression établie dans la chambre intermédiaire 6 , elle provoque l'ouverture du clapet aval 11 et le fluide peut désormais s'écouler par l'embout 5 , comme indiqué par la flèche 16.

If on the other hand, the pressure of the upstream fluid increases until causing the circulation of the liquid in a normal manner in the direction indicated by the arrows 15 and 16, in FIG. 2, the following operations are observed successively:

• - At first, the valves 7 and 11 both remaining closed, the pressure increase in the chamber 30 begins by lowering the central part of the membrane 3, that is to say the seal 28 takes off from its seat 29 ;
• - immediately, the upstream pressure begins to interest the entire surface of the upper face of the membrane 3, the central part of which then lowers quickly by compressing the spring 26, until the shutter 18 comes apply tightly on its seat 17, as well as the valve 21 on its seat 22; henceforth, the intermediate chamber 6 no longer communicates with the outside;
• - At this time, due to the set of calibrations of the various springs and the dimensioning of the surfaces concerned by the pressure, the upstream valve 7 opens and a pressure below the upstream pressure 15 is established in the intermediate chamber 6;
• - once this pressure has been established in the intermediate chamber 6, it causes the downstream valve 11 to open and the fluid can now flow through the nozzle 5, as indicated by the arrow 16.

If the current stops, the valves 7 and 11 close again. Due to the different calibrations of the springs, the pressure in the intermediate cavity remains lower than that in the end piece 4. The relief valves 18 and 21 remain on the seat 17 and 22.

• 1°) dans le cas d'une surpression aval , on observe la fermeture des clapets 7 et 11 . Le clapet 11 interdit tout etour du fluide aval dans la cavité intermédiaire . Si par contre , le clapet 11 devient défectueux , la pression aval s' installe dans la cavité intermédiaire jusqu'à ce qu'elle devienne suffisante pour ouvrir les clapets de décharge 17 , 18 et 21 , 22 . Le liquide pollué provenant de l'aval peut alors s'écouler par les clapets de décharge 17 , 18 , et 21 , 22 ;
• 2°) dans le cas d'une chute de pression amont , on observe la fermeture des clapets 7 et 11 _', La pression amont devient insuffisante par rapport à la pression régnant dans la la cavité intermédiaire , si bien que le ressort 26 soulève la membrane 3 . Ouverture des clapeta 21 , 22 , et 17, 18.Le liquide contenu alors à l'intérieur de la cavité intermédiaire et considéré comme pollué s'écoule alors à l'extérieur par le siège 17 et cet écoulement est d'autant plus rapide que de l'air extérieur est admis par le perçage axial 20 de la tige 19 pour pénétrer dans la chambre 6 au-dessus du niveau du liquide en cours de vidange,lequel liquide est entral- né en tourbillon par le vortex dû aux aubages 25 ;
• 3°) incident possible : la membrane 3 peut se cre- ver en 36 (figure 3) . Dans ce cas , la même pression règne sur les deux faces de la membrane 3 , si bien que le ressort 26 peut agir librement et ouvrir à la fois le clapet de décharge 17 et 18 , et la mise à l'air libre 21 , 22 , comme indiqué sur les figures 1 et 3.

If on the other hand, the current of the liquid tends to reverse, that is to say if the downstream liquid tends to flow back into the nozzle 5, as indicated in FIG. 1 by the arrow 35, which can either due to an increase in the downstream pressure or to a drop in upstream pressure, the following operations are observed:

• 1) in the case of downstream overpressure, the valves 7 and 11 are closed. The valve 11 prohibits any return of the downstream fluid in the intermediate cavity. If, on the other hand, the valve 11 becomes defective, the downstream pressure settles in the intermediate cavity until it becomes sufficient to open the relief valves 17, 18 and 21, 22. The polluted liquid coming from downstream can then flow through the discharge valves 17, 18, and 21, 22;
• 2) in the case of an upstream pressure drop, the valves 7 and 11 _′ are closed, the upstream pressure becomes insufficient relative to the pressure prevailing in the intermediate cavity, so that the spring 26 raises the membrane 3. Opening of the valves 21, 22, and 17, 18. The liquid then contained inside the intermediate cavity and considered to be polluted then flows outside through the seat 17 and this flow is all the more rapid as outside air is admitted through the axial bore 20 of the rod 19 to penetrate into the chamber 6 above the level of the liquid being drained, which liquid is completely born in a vortex by the vortex due to blading 25;
• 3) possible incident: the diaphragm 3 can be created at 36 (figure 3). In this case, the same pressure prevails on the two faces of the membrane 3, so that the spring 26 can act freely and open both the relief valve 17 and 18, and the vent 21, 22 , as shown in Figures 1 and 3.

In this case, although the membrane 3 is punctured, the circulation of liquid normally takes place in the direction indicated by the arrows 15 and 16; the upstream circuit therefore runs no risk of contamination from the polluted downstream circuit 5. Leakage to the membrane manifests on the outside by a flow under the open seat 17. Users therefore have their attention drawn to the incident and they can carry out the repair without having run any risk of contamination for the upstream circuit 4.

In the case of FIG. 1, on the contrary, the downstream circuit tends to push back (arrow 35) while the membrane 3 is punctured. Upstream fluid therefore tends to penetrate through the membrane 3 into the chamber 6 in order to steal towards the exterior through the seat 17 and attract the attention of the users. If the downstream valve 11 is sealed, nothing else occurs. If, on the contrary, the valve 11 is also deteriorated, the downstream liquid discharging into the chamber 6 also flows through the seat of the relief valve 17 18 , the seal 28 being on its seat 29, increasing the flow rate of the leak visible from the outside, but without risking contaminating the clean liquid of the upstream circuit 4.

• - la membrane 3 étant située à la partie haute , l'appareil ne court aucun risque d'ensahlage ou de colmatage par des impuretés véhiculées par un fluide ;
• - l'entrée d'air 20 réalisée par le sommet de la tige crase 19 permet d'accélérer la vidange de la chambre intermédiaire 6 ;
• - en cas de rupture de la membrane 3 , on a une sécurité positive, c'est-à-dire que le ressort ouvre les clapets verticaux 17 , 18 , 21 , 22 , et ferme le 28 , 29 ;
• - il n'existe donc aucun risque de réaspiration vers l'amont même à travers la membrane dana le cas où celle-ci est crevée ;
• ― le vortex créé par les bras inclinés des profilés 25 permet d'accélérer la vidange de la zone morte constituée par la chambre intermédiaire 6 ;
• - le clapet de décharge étant placé plus bas que le clapet amont , il ne peut y avoir aucun risque de réaspiration du liquide stagnant éventuellement dans la cavité intermédiaire lorsque le clapet de décharge 17 , 18 , est ouvert,

We see that the backflow preventer according to the invention has many advantages.

• - the membrane 3 being located at the top, the device runs no risk of ensahlage or clogging by impurities carried by a fluid;
• - The air inlet 20 produced by the top of the flat rod 19 makes it possible to accelerate the emptying of the intermediate chamber 6;
• - in the event of rupture of the membrane 3, there is a positive safety, that is to say that the spring opens the verti valves call 17, 18, 21, 22, and close on 28, 29;
• - there is therefore no risk of re-aspiration upstream even through the membrane in the event that it is punctured;
• - The vortex created by the inclined arms of the profiles 25 makes it possible to accelerate the emptying of the dead zone formed by the intermediate chamber 6;
• the discharge valve being placed lower than the upstream valve, there can be no risk of re-aspiration of the liquid possibly stagnating in the intermediate cavity when the discharge valve 17, 18 is open,

Claims (11)

1 - Hydraulic backflow preventer intended to be interposed between an upstream circuit and a downstream circuit characterized in that it comprises a hollow body (1) provided with an upstream connection end piece (4) and a downstream connection end piece (5) respectively equipped with an automatic spring-loaded valve (7) and an automatic spring-loaded valve (11), while between the seats of these two valves is defined an intermediate chamber (6) at the lower part of which is a fixed seat (17) for a discharge opening which opens towards the outside, this seat cooperating with a discharge shutter (18) located at the lower part of a vertical movable rod (19 ) the upper part of which is connected to a membrane (3) surmounted by a pressure chamber (30) which communicates directly with the upstream connection nozzle (4). 2 - Hydraulic backflow preventer according to claim 1, characterized in that the vertical rod (19) of the discharge shutter ( ₁ 8) is hollow, its lower end being permanently open to the outside, while its upper end is capable of being closed off on a seat (22) integral with the body 1. 3 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that it comprises a spring (26) housed between the fixed part integral with the body (1) and the lower cup (24) and which tends to recall the relief valve in open position. 4 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that this same spring ( ₂ 6) tends to move the shutter (21) away from its seat (22) secured to the body (1). 5 - Hydraulic backflow preventer according to claims 3 and 4, characterized in that the relief valve (18) and the shutter (21) are folded back to the same hollow rod (19), that is to say that they open and close simultaneously. 6 - hydraulic backflow preventer according to any one of the preceding claims, character se in that the lower part of the body (1) at the relief valve has radial arms (25) inclined so as to each define a fixed blade surrounding the movable part (18) of the relief valve inside of the intermediate cavity (6) of the body (1), so as to make appear within the liquid a vortex which increases the speed of emptying of this intermediate zone when the discharge valve (17), (18), opens . 7 - A hydraulic discnnector according to claim 6, characterized in that on the upper face of the membrane 3 is fixed a cup (27) whose annular seal (28) is capable of cooperating with a fixed seat (29) communicating with the upstream pressure chamber (30). 8 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that the choice of the respective dimensions exposed to the various upstream and downstream pressures, as well as the choice of the setting of the discharge spring when appears between the upstream (4 ) and 1 downstream (5) a pressure difference leading to normal operation, by flow of the liquid in the direction of the arrows 15 and 16 (FIG. 2): a) - simultaneously, the shutter (21) and the discharge valve (18) seal their seats tightly; b) - the upstream valve (7) opens; c) - the downstream valve (11) opens. 9 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that the choice of the respective dimensions exposed to the various upstream and downstream pressures as well as the choice of the setting of the discharge spring when the following cases appear: a) - in the event of upstream depression, the shutter (21) and the relief valve (18) move away from their seats (22) and (17), the air intake by the seat (22) allows accelerated emptying of the intermediate cavity; b) - in the event of upstream overpressure and a leak in the downstream valve 11, the shutter (21) and the relief valve ( ₁ 8) move away from their seats (22) and (17), the polluted liquid s' flowing through the seat (17), this é flow being facilitated when there is significant downstream overpressure, because the polluted liquid also flows through the seat (22). 10 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that it comprises a horizontal membrane (3) located at a level higher than the end piece (4) which avoids deposition of particles by gravity originating essentially upstream by the end piece (4). 11 - Hydraulic backflow preventer according to any one of the preceding claims, characterized in that according to the horizontal position of the seat of the relief valve placed at a level below this upstream valve (7), (8) and at the lowest level of the intermediate cavity, there can be no polluted liquid stagnating in the intermediate cavity and therefore any re-aspiration of this polluted liquid upstream by the nozzle (4).

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