EP0528726A1 - Process and apparatus for controlling a pumping station and modular detection device for such a station - Google Patents

Abstract

The control apparatus for the pumping station comprises at least one pump driven by a motor, a sensor for the delivery pressure of the pump or for the level of a volume, and a minimum delivery flow rate sensor for the pump capable of triggering the stopping of the motor. The minimum flow rate sensor 12 is of a type which does not give rise to a substantial head loss when the pump is in normal operation and consists, for example, of an oscillating flap 14 submerged in the delivery duct 1 of the pump and connected to a switch 10% for controlling the motor, and capable of causing this motor to stop. Application to controlling the operation of pumps capable of undergoing abrupt variations in flow rate. <IMAGE>

Description

The present invention relates to a method for controlling a pumping installation comprising at least one pump driven by a motor, for example an electric motor, a sensor of the pump discharge pressure or of the level of a filled capacity. or emptied by the pump, in which the pump motor is started if the discharge pressure sensor indicates a pressure below a minimum threshold value or the level sensor, a respectively lower level (when filling) or higher (in drain) at a threshold level and the pump motor is stopped when the pressure or level sensor is energized, a minimum flow detector system being arranged in the pump discharge line and said pump being stopped , in the safety or alert position, when after a start delay delay, said minimum flow detector system is not energized.

It also relates to the corresponding control device of a pumping installation comprising at least one pump driven by a motor, for example an electric motor, a sensor of the pump discharge pressure or of the level of a filled or emptied capacity. by the pump, said pressure or level sensor being connected to a control member of the pump motor, as well as a minimum pump discharge flow sensor connected to the control member of the pump motor to trigger the said stop engine after starting for a time delay if said flow sensor does not indicate the establishment of said minimum flow.

The invention also applies to modular detection elements for such pumping installations.

• la pompe est mise en marche lorsque la pression d'utilisation ou du réseau devient inférieure à une valeur de seuil;
• la mise en marche est confirmée à condition que l'on constate l'apparition d'un débit de refoulement après un délai de temporisation prédéterminé; et
• la pompe est arrêtée lorsque le débit de refoulement devient inférieur à une valeur prédéterminée correspondant normalement à un quasi-équilibre entre la pression du réseau alimenté par la pompe et la pression maximale de refoulement de la pompe.

The pressure-flow controls for pump operation are well known. They generally consist in using a principle of enslavement according to which:

• the pump is started when the operating or network pressure falls below a threshold value;
• the start-up is confirmed on condition that the appearance of a delivery flow after a predetermined time delay; and
• the pump is stopped when the delivery flow becomes lower than a predetermined value normally corresponding to a quasi-equilibrium between the pressure of the network supplied by the pump and the maximum delivery pressure of the pump.

Unfortunately, this principle of enslavement is ill suited to the use of the most efficient types of pump which have either excellent yields or very high resistance in the event of passage of solid particles, because these types of efficient pump are in general with a very flat pressure-flow characteristic. In other words, when such pumps reach their maximum total discharge pressure, their flow rate is unstable and varies considerably for very small variations in the discharge pressure. The safety stop of such pumps must therefore be carried out as soon as the pump does not reach a minimum flow rate, otherwise the pump will suffer serious damage as a result of the rotation of the pump rotor without the flow of liquid.

A control device of this kind is already known for pumps, in which the opening of the discharge valve of the pump is monitored and the pump is stopped after a delay time at start-up if the discharge valve does not don't open. Such a device does not cannot be used when there is no discharge valve or when it is not accessible and, in general, when it is necessary not to induce additional pressure drops in the pipe delivery due to the installation of a pump running regulation system. Experience has also shown that maintaining the opening of the discharge valve is not an absolute criterion for pump discharge. In fact, the pump discharge valves, when they are dirty or corroded after a long running time of the pump, tend to have a very high hysteresis and to remain in the open position as long as a flow opposite to the backflow does not manifest itself, which leads to keeping the discharge pumps in the running position after the emptying of the tank (s) they control and therefore to the rapid degradation of the pumps thus regulated.

It has been proposed according to FR-A-828 814, to detect a minimum discharge flow rate of a pump, to use a flow detector with a vane partially submerged in the discharge line but causing only small pressure losses for the normal discharge flow. Such a detector is coupled to an installation for starting the electric motor of the pump which cuts off the electric supply to the pump if a sufficient flow rate of the pump is not established after a start-up delay. Such electromechanical devices require a mobile leaktight passage of the discharge pipe. The tightness of such a mobile crossing is likely to deteriorate over time and these electromechanical devices are, moreover, very sensitive to fouling, especially if the pump carries charged liquids.

The present invention proposes to overcome the drawbacks of known pump control systems, by using pressure and minimum safety flow detectors which do not penetrate the pump discharge line and which are thus more reliable and more faithful. than the detectors used so far, while being more sensitive.

To this end, according to the invention, the method of controlling a pumping installation is characterized in that, in the minimum discharge flow detector system, a heating element applied to the external wall of the supply line is used. pump discharge, a first temperature sensor of the temperature of the external wall of the discharge pipe, placed at a sufficient distance from the heating element so as practically not to be subjected to the thermal influence of this heating element and a second temperature sensor of the external wall of the discharge line, placed near the heating element to be heated by the latter in the absence of a significant flow of liquid in the discharge line, as well as a circuit electric and / or electronic comparison of the heating of the first sensor compared to the second, to indicate the absence of a sufficient delivery flow in case significant heating of the second sensor relative to the first.

When the method according to the invention is applied to the regulation of an evacuation pump without an inlet valve, capable of emptying a collection basin, a pressure sensor is used permanently mounted and sealed on the discharge pressure line to detect the height of the liquid in the collection tank and trigger the starting of the pump motor after exceeding a first pressure threshold value and, on the other hand, initiate the stopping of the pump when the pressure in the discharge line becomes lower than a second pressure threshold value close to atmospheric pressure. The pump motor is stopped, after a start delay delay, in the event that said pressure sensor does not indicate a discharge pressure greater than a third minimum threshold value, itself greater than the maximum static pressure liquid from the collection basin.

The control device of a pumping installation according to the invention is characterized in that the minimum flow sensor is constituted by a heating element applied to the external wall of the delivery pipe of the pump, by a first temperature sensor of the external wall of the discharge line, placed at a distance from the heating element sufficient to practically not measure overheating even in the absence of circulation of liquid in the line of discharge, by a second temperature sensor of the external wall of the discharge line, placed near the heating element to be heated by the latter when no liquid circulates in the discharge line, and by an electrical circuit and / or electronic comparison of the heating of the first sensor with respect to the second, capable of determining by this comparison the establishment of a minimum delivery rate of the pump. The first temperature sensor can be placed in a position which is substantially diametrically opposite the heating element and / or the second sensor on the outer wall of the discharge pipe. The second temperature sensor can be placed near and downstream of the heating element with respect to the normal direction of delivery of the pump liquid, so as to detect turbulent delivery of the pump.

According to another embodiment of the invention, the first temperature sensor is placed close to and upstream of the heating element with respect to the normal delivery direction of the pump, so as to detect a low flow pump discharge.

The pump control device according to the invention, applicable to the regulation of an evacuation pump without an inlet valve, capable of emptying a collection basin is characterized in that it comprises a sensor for pressure mounted on the pump discharge line and connected to a control member of the pump motor capable, on the one hand, of triggering the starting of the pump as soon as the pressure sensed in the discharge line exceeds a first threshold value corresponding to a predetermined level in the collection basin and indicative of the filling state of the collection basin and, on the other hand, to trigger the stopping of the pump when the pressure sensed in the discharge line is less than a second threshold value indicative of the state of emptying of the collection basin and in that said pressure sensor is connected to the control member of the pump through a circuit of safety causing the pump motor to stop in the safety or alert position when, after a time delay when the pump motor starts, the pressure sensed in the discharge line is less than a third threshold value, itself greater than said first threshold value and corresponding to the normal discharge operation of the pump.

When the pumping installation includes a level detector, the latter includes an electrical resistance, the value of which is clearly variable as a function of the temperature and which is arranged substantially at the set level to be regulated by the pumping installation, the resistance electric current is traversed by a substantially constant electric heating current, so that the resistance is hot when the pumped liquid has not reached the set level and is significantly cooler when immersed in the pumped liquid which has reached the setpoint level, and a member for comparing the resistance values is capable of delivering a deviation signal, indicating that the setpoint level has been reached.

A modular element for detecting a minimum liquid flow rate in a liquid delivery pipe, intended in particular for implementing the method for controlling a pumping installation as described above, is characterized in that it comprises , inside an interface box, a ceramic membrane intended to be placed in direct contact with the outside of a discharge pipe and on which are fixed at least one first temperature sensor with variable electrical resistance in as a function of temperature and at least one second temperature sensor with variable electrical resistance as a function of temperature and with local electrical heating, this second sensor being placed at a distance from the first and in that said two temperature sensors are each connected to at at least one electrical connection terminal opening to the outside of the interface box and intended to be connected to at least one electrical and / or electronic control member. The modular detection element further comprises at least one pressure sensor with an electrical strain gauge fixed on the ceramic membrane and connected to at least one electrical connection terminal opening out of the interface box.

The modular element can be fixed by its ceramic membrane and, where appropriate, its interface box, on a pipe section which can be inserted in leaktight manner between two parts of the discharge pipe in order to ensure the continuity of the latter and is made of a material that is a good conductor of heat, for example metal, to constitute with said pipe section, an intermediate block for detecting flow and, where appropriate, of temperature and pressure, liquid discharged into the discharge line. The ceramic membrane and, where appropriate, the interface box are permanently fixed to the pipe section to form a removable intermediate block for detecting flow and, where appropriate, temperature and pressure, of the liquid discharged into the discharge line. The pipe section may have two sealed insertion ends, for example flanges, on the discharge pipe and, between these two ends, at least one section of pipe of reduced thickness capable of being subjected to tensile stresses. or significant compression under the effect of the discharge pressure and on the external surface of which the ceramic membrane is bonded or otherwise adhered to which are fixed at least two temperature sensors and, if necessary, at least one pressure sensor with electric strain gauge.

According to another embodiment of the modular element, the wall of the pipe section is traversed by a passage which is closed transversely by the support of generally planar shape and which is applied in a sealed manner by its periphery to an annular shoulder of support provided in said passage, in order to delimit on the support a central zone which comes, on the internal side, into direct contact with the pumped liquid and which carries, on the external side, said sensors or resistance strain gauge integrated into said support which is made of a material good conductor of heat under a thickness capable of withstanding, in the central zone, the discharge pressure of the liquid which nevertheless produces, on said central zone of the support, significant tensile and / or compression stresses.

The periphery of the support bears at least one seal interposed between the annular shoulder of the passage and the support and a rigid clamping ring resting on the body of the pipe section presses the support towards the shoulder.

• la figure 1 représente schématiquement la conduite de refoulement d'une pompe équipée d'un dispositif de commande à palette de détection de débit d'un type partiellement connu;
• la figure 2 représente le diagramme pression-débit des pompes utilisées en combinaison avec le dispositif de commande de la figure 1 et les dispositifs de commande de pompe selon l'invention;
• la figure 3 représente schématiquement un système capteur de débit minimal de refoulement de pompe, complètement extérieur à la conduite de refoulement et utilisant un élément chauffant, selon un premier mode de réalisation du dispositif de commande de pompe selon l'invention;
• la figure 4 représente schématiquement une variante du système capteur de débit minimal de refoulement de la figure 3;
• la figure 5 représente, en coupe schématique, une installation de pompage pour un bassin de rétention, équipée du dispositif de commande selon l'invention;
• la figure 6 représente schématiquement un élément modulaire de détection de débit minimal et, le cas échéant, de pression et de température instantanées pour une conduite de refoulement de pompe. Cet élément est raccordé et intégré à un dispositif de commande d'installation de pompe selon l'invention et peut être installé sur la conduite de refoulement ou faire partie d'un tronçon amovible de cette conduite de refoulement;
• la figure 7 représente schématiquement un premier mode de réalisation des circuits électriques montés à l'intérieur de l'élément modulaire de la figure 6;
• la figure 8 représente schématiquement un deuxième mode de réalisation des circuits électriques montés à l'intérieur de l'élément modulaire de la figure 6;
• la figure 9 représente schématiquement un autre mode de réalisation plus compact de l'élément modulaire de la figure 6.

Other objects, advantages and characteristics will appear on reading the description of various embodiments of the invention, given without limitation and with reference to the appended drawing in which:

• FIG. 1 schematically represents the discharge line of a pump equipped with a control device with a flow detection paddle of a partially known type;
• FIG. 2 represents the pressure-flow diagram of the pumps used in combination with the control device of FIG. 1 and the pump control devices according to the invention;
• FIG. 3 schematically represents a sensor system for minimum pump discharge flow rate, completely external to the discharge line and using a heating element, according to a first embodiment of the pump control device according to the invention;
• Figure 4 schematically shows a variant of the minimum discharge flow sensor system of Figure 3;
• FIG. 5 represents, in diagrammatic section, a pumping installation for a retention basin, equipped with the control device according to the invention;
• FIG. 6 schematically represents a modular element for detecting minimum flow rate and, where appropriate, instantaneous pressure and temperature for a pump discharge line. This element is connected and integrated into a pump installation control device according to the invention and can be installed on the discharge line or be part of a removable section of this discharge line;
• FIG. 7 schematically represents a first embodiment of the electrical circuits mounted inside the modular element of FIG. 6;
• FIG. 8 schematically represents a second embodiment of the electrical circuits mounted inside the modular element of FIG. 6;
• FIG. 9 schematically represents another more compact embodiment of the modular element of FIG. 6.

There is shown diagrammatically in FIG. 1 a device for regulating the running of a pump (not shown), installed on a section 1 of the discharge pipe of the pump connected to a flange 2 of this section. This partially known device comprises a pressure sensor 3, shown here diagrammatically by a pressure transfer passage 4 and by a bellows 5 carrying an electrical switching plate 6 pushed back by a calibrated spring 7 against the effect of the pump discharge pressure. Electrical contacts 8 and 9 are connected to a control member 10 of the electric motor (not shown) of the pump in a provision establishing the electrical circuit also as long as the pump pressure does not exceed a predetermined value.

The device 11 for regulating the operation of the pump comprises a sensor 12 for the minimum delivery rate of the pump which does not cause any significant pressure drop during the operation of the pump. The sensor 12 is connected, by a two-conductor cable 13, to the control member 10 of the electric motor of the pump, via a delay member 10 'which does not trigger the possible stopping of the pump motor until after a start-up delay of a few seconds, in the event that the circuit of cable 13 is not closed.

The highly sensitive flow sensor 12 here comprises a pallet 14 mounted suspended oscillating about an axis 15 and which projects inside the discharge pipe 1 when no flow passes through this pipe or when the flow which passes through this conduct is very weak. The pallet 14 is mounted inside a housing 16 substantially in the general shape of a segment of a circle extending here substantially over an eighth of a circle. To also allow the correct operation of the pallet in positions where it is not arranged vertically, a spring 17 can be placed in abutment on the housing 16 to push the pallet 14 towards the position represented in FIG. 1 when it is biased towards position 14 ′, shown in dotted lines, by the discharge flow which flows in line 1 according to arrow 18.

When a large flow, corresponding to the normal delivery flow of the pump, flows according to arrow 18, the pallet 14 is pushed back against a stop 19 in the position 14 ′ and practically disappears completely in the housing 16 thereby eliminating almost all of the additional pressure losses caused by the flow sensor 12. The pallet 14 is extended out of the housing 16 by a contact blade 20 which is capable of establishing the continuity of the electrical circuit between two contacts sliding electrics 21 and 22, each connected to a separate wire from the conductive cable 13. A housing 23 covers the entire sensor pressure 3 and the flow sensor 12, allowing the connection cables to pass through, if necessary in a sealed manner, to the control member 10 of the electric motor. This member 10 can be placed at a distance from the regulation device 11 and close to the electric motor and can be connected to a complex regulation assembly, to a computer for example, as well as to means of remote signaling of an incident.

The operation of the pump regulation device 11 shown in FIG. 1 is explained in relation to the diagram in FIG. 2 in order to allow a better understanding of the pump control device according to the invention which will be presented below. The electric motor of the pump is switched on to allow it to start when the operating pressure of the liquid network on which the pump is discharged is below a predetermined value. This minimum pressure value which triggers the starting of the engine is in fact determined by the setting of the spring 7 which causes the support of the switching plate 6 on the two contacts 8 and 9 to establish the continuity of the engine starting circuit. pump inside the control member 10. The delay member 10 ′ is then energized and ensures the excitation of the pump operating relay for a few seconds corresponding to the duration of speeding up of the rotor of the pump. If the pump is started correctly, a normal liquid flow rate is established very quickly according to arrow 18 and the diagram of the pump pressure P as a function of the flow rate Q is established on the value of normal flow rate Q _N for a discharge pressure P _N. The flow flowing along arrow 18 rotates the pallet 14 to its position 14 ′ against the return force of gravity and the return spring 17. The pallet 14 bearing on the stop 19 s practically clears the flow circuit without causing any additional pressure drop and establishes, by the contact blade 20, the continuity of the electrical circuit between the sliding contacts 21 and 22. The circuit of the conductive cable 13 then maintains the excitation of the time delay relay 10 ′ and the pump continues to operate after it has started.

When the back pressure of the liquid network increases, the pump which was working at the coordinate point Q _N -P _N on the operating diagram shown in FIG. 2, tends to move its operating point towards the higher pressures. As can be seen in the diagram in FIG. 2, for a very small increase ΔP in the discharge back pressure, the flow rate of the pump collapses completely. Such a situation corresponds for example to the abrupt stop of consumption on a water network, the decreasing flow which flows before the complete stop of the corresponding flow being due, for example, to the expansion of the pipes and tanks of water under the effect of overpressure and the compressibility of the volume of water pressurized. When the delivery flow becomes less than a minimum flow Q _m , the pallet 14 urged by gravity and by the return spring 17, falls back into the position of FIG. 1, which cuts the circuit between the contacts 21 and 22 and causes the pump motor to stop safely.

In the event of an incident when the pump is started, for example if the suction valves of the pump remain stuck to the closure or blocked by solid materials, the minimum flow rate Q _{m is} not established and, after the delay of start delay of the delay member 10 ′, the powering up of the pump motor is interrupted and an alert or incident signal is triggered.

The electromechanical pump control device which has just been described works correctly in new condition, but it has been found to be very sensitive to fouling and corrosion. To avoid this drawback, the paddle flow sensor 12, which does not cause any significant pressure drop during the pump's operation, was replaced by a static flow sensor, operating for example according to the principle of gauges. electrical and / or electronic measurement constraint. In certain installations for pumping a fluid at a very variable temperature, such as drinking water, it is proposed, according to the invention, to use a simpler and more reliable flow sensor, operating by heat dissipation. Such a sensor represented schematically in Figures 3 and 4 shows no entry into the fluid circuit that is likely to induce leakage or corrosion. These heat dissipation flow sensors consist of a heating element A with substantially constant thermal power and comprising an electrical resistance supplied by a circuit 25 giving off a substantially constant thermal power and which is applied to the metallic external wall of the discharge pipe of the pump, for example using a collar 24 surrounding the discharge pipe 1. Two temperature measuring members (or sensors) B and B ′ are arranged on said outer wall, respectively a first member B at a distance from the heating element A with respect to the direction of flow 26 of the liquid inside the metal pipe 1 for discharging the pump and a second member B ′, placed downstream or upstream but close to the heating element A, to measure the proximity heating caused by this heating element A.

Thanks to this arrangement of the heating element A and of the two organs B, B ′ for measuring the temperature, when the discharge flow rate of the pump is high, the dissipation of the heat provided by the heating element, by the intermediate of the fluid discharged by the pump, is large and the difference between the temperatures measured by the first B and the second B ′ temperature measuring members is small. On the other hand, when the discharge flow rate of the pump is low or zero, the heat supplied by the heating element A dissipates only slowly and over a large area around this heating element and the difference between the temperature measured by the first member B and that measured by the second measurement member B ′ becomes significant, which indicates the non-establishment of the normal delivery flow of the pump.

The first temperature measuring device B can, for large diameter delivery pipes, be diametrically opposite the heating element, as shown in dotted lines in the figure with the index (B), which makes it possible to reduce the size along the axis of the discharge line of the pump, external sensors attached by collars or other means on this line. The temperature measuring members B, B ′ can be of any type, in particular consisting of resistors with a negative or positive temperature coefficient which have the advantage of being well integrated in the system for determining the minimum flow rate. Element A with electrical resistance (low power, for example 3 W) can be thermally isolated from the outside environment and applied directly to the wall of the discharge pipe.

Note also in Figure 3 that the second sensor B 'is placed upstream of the heating element A relative to the normal flow direction 26 in this pipe. This has the consequence that, as soon as a low delivery rate occurs in the delivery pipe 1, the surface of the pipe 1 in the vicinity of the sensor B ′ is cooled by the flow (in principle still laminar) of the pumped liquid by the pump. It is of course assumed that the discharge pipe 1 is metallic, for example steel, and has a small thickness, which gives it good thermal conductivity to the outside. Such an arrangement of the sensor B ′ is therefore particularly suitable for capturing low delivery rates. If the liquid discharged by the pump is hotter than the discharge line 1, which may be the case for example in central heating installations, the indication of the establishment of a discharge flow is delayed by the duration necessary to heat the external surface of the discharge pipe at the level of the first sensor B. Conversely, in FIG. 4, the sensor B ′ is placed downstream of the heating element, which has the effect, for low flow rates of discharge (with a flow in principle laminar and not turbulent), to bring inside the pipe 1, opposite the second sensor B ′, of the fluid heated by the heating element A and therefore delays the cooling of the second sensor B ′ until the establishment of a turbulent or rapid discharge (for very viscous fluids, the laminar regime persists up to high flow rates). The sensor system according to FIG. 4 is therefore able to ensure that a frank discharge regime has been established at the outlet of the pump.

When the pump is capable of delivering hot liquid (case of central heating for example) on a cold delivery pipe 1, the delay times for equalizing the temperatures measured by sensors B and B ′ are shorter in the FIG. 4 than in the system shown in FIG. 3. On the other hand, there is the risk, in the event of a very low delivery rate being established, of seeing the first sensor B heated, by the hot discharged fluid, at the temperature of the second sensor B ′ before it is influenced by the temperature of the hot liquid discharged. it can be concluded that the minimum flow sensor system shown in Figure 4 is preferable when the pump is not likely to discharge hot liquid replacing a cold liquid, in which case, it is preferable to use the system shown in Figure 3.

The electrical or electronic information (pulses, voltages, etc.) of the two temperature sensors B and B ′ are transmitted to an electrical and / or electronic comparison circuit 27 which transmits information to the pumping installation establishment or non-establishment of the flow similar to that transmitted by the cable 13 shown in Figure 1.

FIG. 5 represents the application of the pump control device to the level regulation of a basin 30 capable of receiving solid matter suspended in a liquid 31 to be evacuated or to be discharged and which can be, in the worst case , a liquid as aggressive as slurry or draining liquid. The discharge pump 32 is immersed in the bottom of the basin 30 and is here driven by an electric motor mounted for example accessible above a cover 34 of the basin, its rotor being connected to the motor by a vertical shaft 35. In order to as well as possible to avoid the risk of obstruction, the dewatering pump 32 is mounted without suction valve and is, for example, placed on the bottom of the basin 30, along its vertical axis, by a suction strainer in crown 35 provided with large section openings 35 ′. The discharge line 36 of the pump is, for example, detachably connected to a discharge circuit 37 permanently mounted and of large section, that is to say not risking blockage by entangled solids.

A pressure sensor 38 connected to a control member 39 of the pump motor 33 is mounted on the discharge circuit in a leaktight and reliable manner. A discharge valve, in particular a simplified return discharge valve by gravity such that a ball valve 40 can be provided on the discharge circuit 37 upstream of a discharge pipe 41 to a discharge (to the sewer or to drainage tanks). A removable manhole 42 allows for example to access the ball valve 40 to carry out its maintenance.

Since the pump 32 does not have a suction valve (s), the liquid from the basin 30 passes freely through it and the level N of the basin is found practically unchanged in the discharge circuit 37. The sensor 38, which is for example a sensor waterproof and precision static, is in fact capable, by measuring the pressure prevailing in the circuit 37, of indicating the level of the basin 30 when the pump 32 is not operating. The control member 39 of the motor 33 of the pump can be associated with a logic circuit 42 ′ which is capable of sending, by a cable 43, an alert signal when, during a period of stopping of the motor 33, the pressure at sensor 38 exceeds that corresponding to normal level N.

We will now describe the operation of the pump control device associated with the retention tank 30. When the liquid level 31 in the retention tank exceeds the normal level N, the pressure sensor 38 indicates to the control member 39 of the pump motor 33 exceeding a first threshold value, which causes the motor to start through a time relay 44. This relay 44 provides a safety circuit that stops the pump motor 33 in the safety position (manual reiteration only) or alert when, after the expiration of the delay time (ten seconds for example) at starting the engine 33, the pressure at the sensor 38 in the discharge circuit 37, upstream of the ball valve 40, does not reach a third threshold value corresponding to the normal discharge pressure of the pump, this third threshold value being significantly higher than that corresponding to the normal level N, as a result of pressure losses. A second threshold value is constituted by a value of the pressure at sensor 38 which is very low, that is to say close to atmospheric pressure.

When the collection basin 30 is almost completely emptied, alternating puffs of air, liquid materials and sometimes quasi-solid or viscous materials are sucked through the suction openings 35 and are discharged by the pump rotor. through the ball valve 40 in an emulsion which flows at the outlet 41 ′ of the pipe 41, until the pressure drops suddenly in the discharge circuit 37 as a result of an excess of air leading to the decohesion of the emulsion. Continued operation of the pump 32 would then lead to seizure of the bearings thereof, but, fortunately, the sensor 38 registers zero or negative pressure (after the closure of the ball valve 40, the fall of the emulsion may temporarily put the top of the discharge circuit 37 in vacuum) which, on the one hand, accelerates and confirms the closing of the ball valve 40 and, on the other hand, leads to the overrun by zero or negative pressure values, of the second pressure threshold value, causing the pump motor to stop.

The pump is then kept stopped then, as the basin 30 is filled, the level of the latter is transmitted through the pump to the discharge circuit 37 to come again to request the pressure sensor 38 when he reaches this one. Thanks to the control circuit and pump regulation according to FIG. 5, it is possible to use a single pressure sensor 38 permanently mounted and sealingly on the discharge circuit 37. The number of sensors must in fact be as small as possible since these These are always expensive to install and maintain in good working order and precision, both to monitor the level of the tank and the operation of the pump in discharge. In the case where the basin 30 is only intended to contain liquids little or not loaded with solid products, to monitor the establishment of the discharge pressure of the pump, it would be possible to use the flow sensor systems shown in Figures 3 and 4 to ensure the safety start of the pump.

In addition to the pressure sensor 38, it is possible to use, for the level sensor N of a collection or reserve basin, sensors of any type, electro-mechanical or purely electrical or electronic. One type of sensor which has been found to be very reliable for pumping equipment according to the invention consists of an electrical resistor 45, the value of which is clearly variable as a function of temperature and which is housed, for example, in a tube. protection 46 open at both ends to allow free rise of the liquid inside the tube. The resistor 45 is placed just at the level N desired for the liquid and is maintained at a temperature above ambient by an electrical circuit with annexed electronic adjustment or with self-regulation. The electrical resistor 45 can be supplied with low voltage and may come into direct contact with the liquid discharged by the pump if the latter is not very conductive, or else it is protected in an insulating sheath which nevertheless ensures cooling. energetic when the resistor 45 is immersed in the liquid. The resistance value is clearly different when it is in air (tank level 30 below level N for example) or in a liquid such as water which causes intense heat dissipation. The deviation of the value of the resistance at room temperature from the hot value of this resistance is checked by a level detection system connected to the resistor 45 by a cable 47 and which does not use moving parts liable to be blocked by corrosion or by the liquid loaded with debris and which is pumped by the installation. A level sensor with heated electrical resistance, immersed or not in the liquid discharged by the pump, depending on whether the set level is reached or not, can be applied to all the control devices of a pumping installation which have just be described and to level control devices of any type.

FIG. 6 shows a modular element for detecting the minimum flow rate of liquid in a discharge line, this modular element being able to replace the assemblies of FIGS. 3 and 4 using separate thermometric resistances placed on the discharge line of the pump and connected to electrical and electronic circuits for comparison and excitation.

The modular detection element 50 shown in FIG. 6 is produced from a ceramic support 51, for example a relatively flexible membrane due to its small thickness and on which are deposited by any suitable means, in particular by screen printing followed of a cooking, electrical resistances highly variable with temperature, with a positive or negative temperature coefficient as the case may be, and which are intended to serve as electrical and / or electronic temperature measurement devices. The membrane 51 is housed in an interface box 49 made of an electrically insulating material and is held in position before the assembly of the modular element by a box cover not shown in FIG. 6.

The membrane 51 thus carries temperature measuring resistors 52, 53, 54, 55 which can be fixed and permanently integrated on the membrane by baking at temperatures up to 900 ° C. Furthermore, stress measurement resistors or strain gauges 56 are deposited or bonded respectively to the interface box 49 and to the membrane 51. It can be recognized in the diagram of the FIG. 7 of the electrical resistors 56a, 56b, 56c, 56d supplied with a DC voltage +/- in groups of two to constitute a strain gauge, for example the resistors 56b to 56d are fixed on the interface box 49 while the resistor 56a is fixed on the ceramic membrane 51 to undergo the surface stresses of a discharge pipe 57. Near or around the temperature measurement resistor 52, an electrical heating resistor 58 of the same type as is arranged heating element A, that is to say of low power (from 3 to 4 W), and which is supplied according to the diagram in FIG. 7 by a source of direct current +/-.

At its external part in service, the interface box 49 is closed, preferably in a sealed manner, by an insulating plate 48 placed at a distance from the membrane 51 and which carries electrical connection pins or terminals corresponding in particular to the measurement resistors fixed in the interface box 49. There is a pin 59 for grounding, pin 60 for the resistor 55, the pins 61 for the resistor 54, the pins 62 for supplying the resistors 56a to 56d and their bridge voltage sampling, terminal 63 of an unused temperature measurement resistor, terminal 64 of resistor 52 and terminals 65 of the DC power supply (notably resistors 55 and 52 and of the resistor heating 58). The terminals 59 to 62 and 64, 65 are connected by cables 59a, 60a, 61a, 62a, 64a, 65a to an electrical control member 10 of a pump delivering on the pipe 57.

The connections with the electrical control member 10 are preferably carried out by means of electronic interface detectors, respectively: 10a for detecting the existence of a minimum flow rate in the discharge line 57, 10b for detecting the temperature of the liquid conveyed in the discharge line and 10c for detecting the discharge pressure, that is to say the absolute pressure prevailing in the discharge line 57. Before mounting, the modular detection element 50 contained in the housing interface 49 is protected on the side of the ceramic membrane 51 by a protective cover, not shown in FIG. 6, which is removed for fixing the membrane to the exterior surface of the discharge pipe 57. The interface box 49 is also fixed on the external surface of the pipe 57, for example by a lateral bonding line 66. It can be seen in FIG. 6 that the connection between a detection resistor 51 to 56 and the corresponding terminal fixed to the insulating plate 48 is made by a flexible wire (see flexible wire 67 for terminal 60, inside the interface box 49).

According to another embodiment of the modular detection element 50, the latter is fixed by its ceramic membrane 51 and, if necessary, by its interface box 49 to a pipe section 70 capable of being inserted from sealingly between two parts 68 and 69 of the discharge line of a pump (not shown) in order to ensure the continuity of the discharge line. The pipe section 70, equipped with its modular detection element 50 removably fixed or permanently fixed to the central pipe part of reduced thickness, thus constitutes a complete removable detector block which can be inserted on a discharge pipe. not suitable for measuring minimum flow and, where appropriate, temperature and pressure, for example because it is too thick or is made of a thermal insulating material (reinforced concrete, insulated metal, synthetic material, etc.).

The insertable pipe section 70 shown in FIG. 6 comprises, at each of its ends, mounting flanges 71 and 72 provided with sealing means such as an O-ring 73, 74 and intended to cooperate by means of assembly screws 68a, 69a with corresponding flanges formed at each of the ends of the delivery pipe parts 68, 69.

Between the mounting flanges, the metal discharge pipe part 57 is formed, for example in a metal that is a good heat conductor such as an aluminum alloy, which quickly takes the temperature of the liquid in transit in the discharge line. The pipe part 57 has a reduced thickness, nevertheless ensuring sufficient resistance to the discharge pressure but which causes significant stresses and therefore electrical deformations to appear on the external surface of the pipe under the effect of the discharge pressure. The reduced thickness also allows rapid transmission of the temperature of the liquid discharged by the pump to the external surface of the pipe 57 on which the resistors 52 to 55 are bonded, by means of the thin ceramic support membrane 51 sensitive to temperature and / or to deformations caused by surface stresses.

According to a first embodiment of the electrical circuits mounted inside the modular element, the differential temperature measurement resistors 52 (heated resistance) and 55 to which the respective indices T1 and T2 are assigned, are supplied by a source of direct current 65 also used for heating, by means of corresponding adjustment resistors RT1 and RT2. A sensor of the differential voltage VS2 between terminals 64 and 60 makes it possible to address to the external minimum flow detector 10a a voltage which is, in principle, directly proportional to the temperature difference T1-T2 between temperatures T1 and T2 and which allows, by threshold adjustment, to detect the minimum admissible delivery flow for the pump after start-up. For a large flow rate in the discharge line 57, the thermal power of the heating resistor 58 is almost completely dissipated in the discharged liquid and the output signal at the terminals 60, 64 is very weak. The output signal on the terminals 61 makes it possible to know at any time the temperature on the external surface of the pipe 57 and to act if necessary when this temperature is too high, which indicates an exaggerated temperature of the fluid discharged by the pump.

The bridge for measuring the discharge pressure of the liquid in the pipe 57 is produced using the resistors 56 to which temperature compensation elements are added, where appropriate: a resistor RP mounted in parallel with the resistor 56c, a resistor RS in series with the resistor 56a and, if necessary, a resistor RM mounted between the two midpoints of the two branches of the measuring bridge. The temperature compensation resistors are necessary if the temperature on the surface of the pipe 57 is liable to vary within large amplitudes. The output signal VS1 picked up at the terminals 62 is sent to the pressure detector block 10c.

The second embodiment of the electrical circuits of the modular element 50, represented in FIG. 8, differs from that of FIG. 7 essentially in that it comprises, for the measurement of the minimum flow, a double bridge of resistors which allows to measure with greater sensitivity differential variations in sensor temperature caused by the discharge flow rate in line 57. In the circuit of FIG. 8, two temperature measurement resistors 52 and 75 (denoted T1, T4) are heated simultaneously by a common heating resistor 58 ′ and are supplied by a continuous current source +/- (terminals 65) in series each with a respective unheated temperature measurement resistor 76 and 55. The differential voltage sensed is thus a function of temperature differences T1.T2-T3.T4 and allows better identification of the relative overheating of the heated resistors 52 and 75.

The mounting of the electrical circuits of the modular element 50 according to the diagram in FIG. 8 is useful, in particular when the fluid circulating in the discharge line 57 (for example hot heating water), is likely to be very hot compared to the ambient.

In the embodiment shown in FIG. 9 where the elements fulfilling the same functions as in FIG. 6 have the same reference numbers, the modular detection element 50 is tightly integrated into a section of pipe 70 which, like the section 70 of Figure 6, is inserted in a sealed manner between two parts 68, 69 of the discharge line of a pump (not shown). The section 70 can, for example, be made of molded plastic (machined for small series) of great thickness to receive the sensor support according to the invention.

A passage 77 is formed perpendicular to the wall of the pipe section by forming an annular shoulder 78 on which the edge (coated with an elastomeric seal 79) is applied to a support 80 of generally planar shape (and here circular) for the sensors: temperature 55, differential temperature 52 for measuring the minimum flow rate and stress (strain gauge not shown) with electrical resistances. The support 80 preferably consists of a relatively thin ceramic disc (thickness of the order of 1 mm) which conducts heat well and which has a diameter preferably between 15 and 30 mm. An advantageous support has been found to have a diameter of 18 mm and its "exposed" central part, which remains free after the application of the elastomeric seal 79 on the shoulder 78 by the tightening effect of a rigid tightening ring 81 , then had a diameter of 10 mm. The simple temperature sensors 55 and differential (heated) 52, practically identical to those represented in FIG. 6, are also deposited by screen printing and fixed by baking at 900 ° C. on the external flat surface of the support 80 in the "exposed" zone. 10 mm in diameter, at a distance from each other, but at a distance of less than 10 mm, which is however sufficient to show the heating effect on the differential sensor 52.

The active resistance 56a (subjected to tensile or compressive stresses) of the strain gauge 56 is generally placed in the center of the exposed area where the maximum flexural stresses exist on the ceramic support 80 of approximately 1 mm d thickness, pinched over its entire periphery by the rigid ring 81 screwed for example into a threaded bore of the passage 77.

The connecting wires of the electrical resistances of the sensors deposited on the support 80, are housed in a sheath 82 at the outlet of the modular detection element 50 and they terminate in a coupler 83 ensuring, in a withdrawable manner, the connection interface with cables 60a, 64a to the minimum flow detector 10a, with the cable 61a to the liquid temperature detector 10b and with the cables 62a for detecting the discharge pressure.

The modular detection element 50, as shown in FIG. 9, is generally produced in the form of a removable block of short length which can be inserted on the discharge line 68, 69 by flanges or else can be screwed onto corresponding end pieces of the discharge pipe, the connection to the electrical control member 10 being effected by the withdrawable coupler 83. The large wall thickness of the section 70 makes it possible to use, for this section, a block of inexpensive molded plastic material which withstands the temperatures of hot water in a central heating circuit without damage. The circuits of FIGS. 7 and 8 are, of course, applicable (in a miniaturized form) on the support 80 with a diameter of 15 to 30 mm shown in FIG. 9.

The modular element 50 which forms an interchangeable block up to the withdrawable coupler 83 may include, in certain applications, a support 80 removable to the coupler 83. In the event of failure of the electrical and / or electronic circuits mounted on the support 80, this is then extracted after unscrewing or removing the ring 81 and is replaced by another support 80 cooperating with the peripheral elastomer seal 79. Given the fragility of the measurement resistors 52 to 56 and the difficulties in coupling them to the pump control member 10, most applications however provide for the complete exchange of the modular detection element 50 with its pipe section 70.

The control devices of a pumping installation delivering on a network or else controlling the level of a capacity filled or emptied by the pump can use the modular detection element 50 fixed on a discharge pipe and connected to a electrical control 10 or else the modular block consisting of the pipe section 70 permanently carrying the modular block 50 detachably connected to the control member 10, to replace the device 11 shown in FIG. 1. The method and the device for controlling a pumping installation according to the invention, as well as the modular detection element which relates thereto, have been illustrated for a pump driven by a electric motor, which is the most common case, but they can, of course, be applied to pumps driven by other motors, such as heat engines.

Claims (16)

1.- Method for controlling a pumping installation comprising at least one pump (32) driven by a motor (33), a sensor (6, 7) of the pump discharge pressure or of the level (N) d '' a capacity (30) filled or emptied by the pump, in which the pump motor is started if the discharge pressure sensor (6, 7) indicates a pressure below a minimum threshold value or a level below or above a threshold level and the pump motor is stopped when the pressure or level sensor is energized, a minimum flow detector system (12) being arranged in the discharge line (1) of the pump and said pump being stopped, in safety or alert position, when after a start delay delay, said minimum flow detector system (12) is not energized, characterized in that one uses, in the system minimum discharge flow detector: - a heating element (A, 58) applied to the external wall of the discharge line of the pump, a first temperature sensor (B) of the temperature of the external wall of the discharge line, placed at a sufficient distance from the heating element so as practically not to be subjected to the thermal influence of this heating element; - a second temperature sensor (B ′) of the external wall of the discharge pipe (1), placed near the heating element (A) to be heated by the latter in the absence of a liquid flow sensitive in the discharge line (1); and an electrical and / or electronic circuit for comparing the heating of the first sensor with respect to the second, to indicate the absence of a sufficient discharge flow rate in the event of significant heating of the second sensor with respect to the first. 2.- Method for controlling a pumping installation comprising at least one pump (32) driven by a motor (33), a sensor (38) of the discharge pressure of the pump or of the level (N) of a capacity (30) filled or emptied by the pump, in which the pump motor is started if the discharge pressure sensor (38) indicates a pressure below a minimum threshold value or a level below or above a threshold level and the pump motor (33) is stopped when the pressure (38) or level (N) sensor is energized, a minimum flow detector system being arranged in the discharge line (37) of the pump and said pump being stopped, in the safety or alert position, when after a start delay delay, said minimum flow detector system is not energized, the pump being an evacuation pump (32) without inlet valve, capable of emptying a collection basin (30), characterized in that a pressure sensor (38) is mounted permanently and so sealed on the discharge line (37) to detect the height of liquid in the collecting tank (30) and triggering the pump start-up after exceeding a first pressure threshold value and, on the other hand, triggering the pump stop when the pressure in the discharge line (37) becomes less than a second pressure threshold value close to atmospheric pressure. 3.- Method according to claim 2, characterized in that the motor (33) of the pump is stopped, after a start delay delay, in the case where said pressure sensor (38) does not indicate a pressure discharge greater than a third minimum threshold value, itself greater than the maximum static pressure of the liquid in the collection basin (30). 4.- Control device for a pumping installation comprising at least one pump driven by a motor, a sensor (56) of the pump discharge pressure or of the level (N) of a filled capacity (30) or emptied by the pump, said pressure or level sensor being connected to a control member (10) of the pump motor, as well as a sensor (12) for minimum pump discharge flow connected to the control member (10) of the pump motor for triggering the stopping of said engine after it has started during a delay time if said flow sensor does not indicate the establishment of said minimum flow, characterized in that the minimum flow sensor is constituted by a heating element (A) applied to the external wall of the discharge line (1) of the pump, by a first sensor (B) of the temperature of the external wall of the discharge line, placed at a distance from the heating element sufficient to practically not not measure overheating even in the absence of liquid circulation in the discharge line, by a second sensor (B ′) of the temperature of the external wall of the discharge line, placed near the heating element for be heated by the latter when no liquid is circulating in said discharge line, and by an electric and / or electronic circuit (27) for comparing the heating of the first ca pteur (B) compared to the second (B ′), able to determine by this comparison the establishment of a minimum pump discharge flow. 5.- Device according to claim 4, characterized in that the first temperature sensor (B) is placed in a position which is substantially diametrically opposite the heating element (A) and / or the second sensor (B ′) on the outer wall of the discharge pipe (1). 6.- Device according to claim 4 or 5, characterized in that the second temperature sensor (B ′) is placed near the heating element (A) and downstream of it relative to the normal direction of discharge (26) pump liquid. 7.- Device according to claim 4 or 5, characterized in that the first temperature sensor (B) is placed near the heating element (A) and upstream thereof relative to the normal direction of discharge ( 26) of the pump. 8.- Control device for a pumping installation comprising at least one pump (32) driven by a motor (33), a sensor (38) of the pump discharge pressure or of the level (N) of a capacity (30) filled or emptied by the pump, said pressure or level sensor being connected to a control member (10) of the pump motor, as well as a minimum pump discharge flow sensor connected to the control member (10) of the pump motor to trigger the stopping of said motor after it has been started for a time delay if said flow sensor does not indicate the establishment of said minimum flow, the device being applied to the regulation of a pump evacuation (32) without inlet valve, suitable for emptying a collection basin (30), characterized in that it comprises a pressure sensor (38) mounted on the discharge pipe (37) of the pump and connected to a control member (39) of the pump motor capable, on the one hand, of starting the starting of the pump (32) as soon as the pressure sensed in the discharge line (37) exceeds a first threshold value corresponding to a level (N) predetermined in l e collection basin and indicative of the filling state of the collection basin (30) and, on the other hand, to trigger the stopping of the pump (32) when the pressure sensed in the discharge line (37) is lower than a second threshold value indicative of the state of emptying of the collection basin and in that said pressure sensor (38) is connected to the control member (39) of the pump through a safety circuit ( 44) causing the pump motor (33) to stop in the safety or alert position when, after a time delay when the pump motor starts, the pressure sensed in the discharge line (37) is lower to a third threshold value, itself greater than said first threshold value and corresponding to the normal discharge operation of the pump. 9. Control device according to claims 4 to 8, characterized in that, when the pumping installation comprises a level detector, the latter comprises an electrical resistance (45) whose value is clearly variable depending on the temperature and which is disposed substantially at the set level (N) to be regulated by the pumping installation, in that the electrical resistance (45) is traversed by a substantially constant electric heating current, so that the resistance is hot when the pumped liquid has not reached the set level (N) and is much colder when immersed in the pumped liquid which has reached the setpoint level (N), and in that a member for comparing the values of the resistance (45) is capable of delivering a deviation signal, indicating that the setpoint level (N) has been reached. 10.- modular element for detecting a minimum liquid flow rate, in a liquid delivery pipe, intended in particular for implementing the control method according to claim 1, characterized in that it comprises a support (51, 57; 80) intended to be placed in direct contact with the fluid flowing in a discharge pipe (68, 69) and on which are fixed at least one first temperature sensor (55) with variable electrical resistance as a function of the temperature and at at least a second temperature sensor (52) with variable electrical resistance as a function of temperature and with electric heating (58, 58 ′) in proximity, this second sensor (52) being arranged at a distance from the first (55) and in that said two temperature sensors (52, 55) are each connected to at least one electrical and / or electronic control member (10). 11.- modular element according to claim 10, characterized in that it further comprises at least one pressure sensor with electric strain gauge (56) fixed on the support (51, 57, 80) and connected to at least one electrical and / or electronic control member (10). 12.- modular element according to claims 10 and 11, characterized in that it is fixed by its support (56, 51) and, if necessary, an interface box (49), on a pipe section (70 ) which is capable of being inserted in a sealed manner between two parts (68, 69) of the discharge pipe in order to ensure the continuity of the latter and is made of a material which is a good conductor of heat, to constitute with said section pipe (70) an intermediate flow detection block and, if necessary, temperature and pressure, of the liquid discharged into the discharge pipe (68, 69). 13.- modular element according to claim 12, characterized in that the support (51, 57) and, where appropriate, an interface box (49) are permanently fixed to the pipe section (70) to constitute a removable intermediate block for detecting the flow rate and, if applicable, the temperature and pressure, of the liquid discharged into the discharge pipe. 14.- modular element according to claim 12 or 13, characterized in that the pipe section (70) has two sealed insertion ends (71, 72), on the discharge pipe (68, 69) and, between these two ends, at least one part of pipe (57) of reduced thickness capable of being subjected to significant tensile stresses or compression under the effect of the discharge pressure and on the external surface of which is bonded or otherwise adhered a ceramic membrane (51) on which are fixed at least two temperature sensors (52, 55) and, if necessary, at least one pressure sensor (56) with an electric strain gauge. 15.- modular element according to claims 10 and 11, characterized in that it is constituted by a pipe section (70) which is capable of being inserted in leaktight manner between two parts (68, 69) of the pipe discharge in order to ensure the continuity of the latter, and the wall of which is traversed by a passage (77) which is closed transversely by said support (80) of generally planar shape and which is applied in a sealed manner by its periphery on a shoulder annular support (78) formed in said passage, in order to delimit on the support (80) a central zone which comes, on the inside, in direct contact with the pumped liquid and which carries, on the outside, said sensors (52, 55) or resistance strain gauge integrated into said support (80) which is made of a material which is good conductor of heat under a thickness capable of withstanding in the central zone the pressure of discharge of the liquid which nevertheless produces, on said central area of the support, significant tensile and / or compression stresses. 16.- modular element according to claim 15, characterized in that the periphery of the support (80) bears at least on a seal (79) interposed between the annular shoulder (78) of the passage (77) and the support (80) and in that a rigid clamping ring (81) bearing on the body of the pipe section (70) presses the support (80) towards the shoulder.

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