EP0084754B2 - Back flow preventer for hydraulic conduits - Google Patents

Abstract

The invention concerns a hydraulic disconnector to separate an inflow circuit from outflow from an outflow circuit. Controlled by the membrane, the valve opens the drainage of chamber if the outflow circuit flows back in the direction of the arrow. The spring opens this drainage even if the membrane 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.

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 up 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 of very complicated realization (see for example US-A-4,244,392). 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.

Document US-A-2 503 424 describes a backflow preventer comprising a hollow body provided with an upstream connection end piece and a downstream connection end piece equipped respectively with an automatic spring-loaded valve and an automatic spring-loaded valve downstream, while between the seats of these two valves is defined an intermediate chamber in which there is, at the same level as the upstream and downstream valves, a valve body having a fixed seat bordering an opening between the intermediate chamber and the interior of the valve body which communicates with the outside via a lateral opening, the seat of the valve body cooperating with a shutter connected to a membrane held on its periphery by the hollow body and surmounted by a pressure chamber which communicates directly with the upstream connection nipple, the underside of the membrane being subjected to the pressure prevailing in the intermediate chamber, so that the shutter does not 'applies to the valve body seat only if the pressure in the upstream connection nozzle is higher than the pressure in the intermediate chamber.

Document FR-A-2 427 532 describes an antireflux device comprising an upstream connection nozzle, a check valve and a safety valve assembly arranged downstream of the check valve, in parallel and outside the connection end piece downstream of the device. The safety valve has in the lower part a separate discharge orifice and an air inlet orifice, each connected to the downstream connection nozzle by a respective passage, the opening or closing of these passages being effected by to a relief valve and an air inlet valve, cooperating with each other and with a membrane maintained on its periphery by the body of the safety valve and surmounted by a pressure chamber which communicates directly with the nozzle of upstream connection, the underside of the diaphragm being subjected to the pressure prevailing in the downstream connection nipple, so that the discharge and air inlet valves only close if the pressure in the nipple upstream connection is greater than the pressure in the downstream connection nozzle. The check valve is of complicated construction, in particular as to the shape of the discharge and air intake passages, and to the manner in which the discharge and air intake seats cooperate, their coupling being effected by a complex equipment of various parts, among which is a third movable seat along a cylindrical wall to ensure the sealed isolation of the discharge and air inlet ducts. In addition, the relief valve being located in one of the branches of a U-bend inverted from the discharge passage, polluted liquid may stagnate under it at the bottom of the body of the safety valve, and be sucked back into the pipe. power supply.

The object of the present invention is to avoid the drawbacks of prior devices by producing a backflow preventer in which any operating incident gives rise to a visible leak from the outside without however allowing any rebreathing of the polluted downstream liquid.

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

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 is defined an intermediate chamber in which there is a fixed seat for a discharge opening which opens towards the outside, this seat cooperating with a discharge shutter connected to a membrane maintained on its periphery by the body and surmounted by a pressure chamber which communicates directly with the upstream connection end piece , the underside of the membrane being subjected to the pressure prevailing in the intermediate chamber; this device being characterized in that said fixed seat for a discharge opening is located at a level below the upstream valve and at the lowest level of the intermediate chamber, so that there can be no polluted liquid stagnating in the intermediate chamber and consequently any re-aspiration of this polluted liquid upstream by the upstream nozzle; and in that said discharge shutter is located at the lower part of a vertical movable rod whose upper part is connected to said membrane, this rod being provided with an axial bore, its lower end being permanently open on the outside, while its upper end which forms an air inlet shutter in the intermediate chamber is capable of being closed off on an air inlet seat secured to the body.

Particular embodiments are the subject of claims 2 to 10.

In particular, the lower part of the intermediate chamber is formed of inclined blades so as to cause a vortex to appear within the liquid, which increases the speed of emptying of this intermediate zone when the discharge valve opens. 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.

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

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

• Fig. 1 is a view in longitudinal section of a backflow preventer according to the invention in the rest position.
• Fig. 2 is a similar section when the backflow preventer is in the normal operating position.
• Fig. 3 illustrates the operation during a possible incident, namely when the membrane is punctured.
• Fig. 4 is a section on IV-IV (fig. 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 tip 4 and a downstream connection tip 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 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 so as 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 inlet.

The lower part of the intermediate cavity is formed of inclined blades 25 so as to make appear within the liquid a vortex or vortex increasing the speed of emptying of the liquid in this zone when the discharge 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 thus defined inside the cover above the upper cup 27 on its seat 28. This pressure chamber communicates directly with the upstream connection end piece 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 clapet 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 étanche 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 keeps 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 ressort 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 communique 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 la 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 increase in pressure 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 rapidly 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; now, 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 retour 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 cavité intermédiaire, si bien que le ressort 26 soulève la membrane 3. Ouverture des clapets 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 entraîné en tourbillon par le vortex dû aux auba- ges 25;
• 3) incident possible: la membrane 3 peut se cre- ver en 36 (fig. 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 fig. 1 et 3.
  Dans ce cas, bien que la membrane 3 soit crevée, la circulation de liquide s'effectue normalement dans le sens indiqué par les flèches 15 et 16; le circuit amont ne court donc aucun risque de contamination de la part du circuit aval pollué 5. La fuite à la membrane se manifeste à l'extérieur par un écoulement sous le siège ouvert 17. Les utilisateurs ont donc leur attention attirée sur l'incident et ils peuvent effectuer la réparation sans avoir couru aucun risque de contamination pour le circuit amont 4.

If on the other hand, the flow 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 arrow 35, which may be due either to an increase in the downstream pressure; either at an upstream pressure drop, the following operations are observed:

• 1) in the case of a downstream overpressure, the closure of the valves 7 and 11 is observed. 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 the 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 lifts 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 faster as the 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 entrained in a vortex by the vortex due to the blades 25;
• 3) possible incident: the membrane 3 can be created at 36 (fig. 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 fig. 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 is manifested 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 mem brane 3 is punctured. Upstream fluid therefore tends to penetrate through the membrane 3 into the chamber 6 to flow outward through the seat 17 and attract the attention of users. If the downstream valve 11 is sealed, nothing else happens. 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 in the upstream circuit 4.

• - la membrane 3 étant située à la partie haute, l'appareil ne court aucun risque d'ensablage ou de colmatage par des impuretés véhiculées par un fluide;
• - l'entrée d'air 20 réalisée par le sommet de la tige creuse 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 dans 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.

It can be seen that the backflow preventer according to the invention has numerous advantages. In particular:

• - the membrane 3 being located in the upper part, the device runs no risk of sanding or clogging by impurities carried by a fluid;
• - The air inlet 20 produced by the top of the hollow rod 19 makes it possible to accelerate the emptying of the intermediate chamber 6;
• - In case of rupture of the membrane 3, there is a positive safety, that is to say that the spring opens the vertical valves 17.18,21,22, and closes 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. A hydraulic disconnecting apparatus intended to be interposed between an up-flow circuit and a down-flow circuit, comprising a hollow body (1) provided with an up-flow connection socket (4) and a down-flow connection socket (5) fitted respectively with an up-flow automatic spring valve (8, 9, 10) and a down-flow automatic spring valve (12,13,14), whilst between these two valves there is formed an intermediate chamber (6) in which there is a fixed seat (17) for a discharge aperture which opens to the exterior, this seat (17) cooperating with a discharge stop (18) connected to a diaphragm (3), held on its periphery by the body (1) and surmounted by a pressure chamber (30) which communicates directly with the up-flow connection socket (4), the lower face of the diaphragm (3) being subject to the pressure in the intermediate chamber; this apparatus being characterized in that said fixed seat (17) for a discharge aperture is located at a level below the up-flow valve (8, 9, 10) and at the lowermost level of the intermediate chamber (6), so that there cannot be any polluted liquid stagnating in the intermediate chamber (6) and consequently any possible suction of this polluted liquid towards the up-flow through the up-flow connection socket (4); and in that said discharge stop (18) is located at the lower end of a movable vertical stem (19) of which the upper end is connected to said diaphragm (3), said stem (19) being provided with an axial boring (20), its lower end being permanently opened to the exterior, whilst its upper end which forms air inlet stop (21) in the intermediate chamber (6) may seal an air inlet seat (22) integral with the body (1).

2. A hydraulic disconnecting apparatus according to claim 1, characterized in that said air inlet seat (22) is located at the lower part of a chamber integral with the body (1) communicating with the upper end of the axial boring (20).

3. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized in that the movable vertical stem (19) is provided with radial arms (23) passing through a fixed intermediate seat, integral with the body (1), for getting held on a lower cup (24) located under the diaphragm (3) so that the motion of the latter is made common to the valve (18) for discharge stopping and the air inlet stop (21), a spring (26) being housed between the intermediate seat and the lower cup (24) and tending to return the discharge valve (18) to open position and to move the air inlet stop (21) away from its seat (22) integral with the body (1).

4. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized in that said diaphragm (3) is horizontal and located at a level above the upper socket (4), which avoids a deposit through gravity of particles coming mainly from the up-flow through the socket (4).

5. A hydraulic disconnecting apparatus according to claim 3, characterized in that the air inlet stop (21) and the discharge valve (18) are connected to the same stem, so that they open and close simultaneously.

6. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized in that the fixed seat (17) of the discharge valve (18) is horizontal.

7. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized in that the lower part of the body (1) at the level of the discharge valve has some radial arms (25) each inclined so as to form a fixed blade surrounding the moving part (18) of the discharge valve inside the intermediate chamber (6) of the body (1), so as to cause a vortex to appear in the liquid, this vortex increasing the draining speed of this intermediate zone when the discharge valve (17, 18) opens.

8. A hydraulic disconnecting apparatus according to claim 7, characterized in that a cup (27) is fixed to the upper face of the diaphragm (3), the annular seal

(28) of this cup (27) being able to act in conjunction with a fixed seat (29) which communicates with the up-flow pressure chamber (30).

9. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized by the choice of the respective dimensions of the components exposed to the various up-flow and down-flow pressures, as well as the choice of the calibration of the discharge spring, in such a way that when a pressure difference leading to normal operation of up-flow to down-flow movement of the liquid appears between the up-flow (4) and the down-flow (5):

a) simultaneously, the stop (21) and the discharge valve (18) move to seal their seats;

b) the up-flow valve (8, 9, 10) opens;

c) the down-flow valve (12, 13, 14) opens.

10. A hydraulic disconnecting apparatus according to any one of the preceding claims, characterized by the choice of the respective dimensions of the components exposed to the various up-flow and down-flow pressures, as well as the choice of the calibration of the discharge spring, in such a way that

a) in the case of an up-flow depressurisation, the air inlet stop (21) and the discharge valve (18) move from their seats (22,17), the entrance of air through the seat (22) allows an accelerated evacuation of the intermediate chamber;

b) in the case of an excessive down-flow pressure and a leak at the up-flow valve (8, 9, 10), the air inlet stop (21) and the discharge stop (18) move from their seats (22, 17), the polluted liquid flowing out through the seat (17) of the discharge valve (18), this outflow being facilitated when there is a large excess of down-flow pressure, for the polluted liquid can also flow through the air inlet seat (22).

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