FR2645213A1 - MOTOR PUMP GROUP WITH PRESSURE AND FLOW SENSORS - Google Patents

Abstract

It includes a pump 1 with delivery pipe 2, a motor-variator 4 driving the pump 1 in rotation and an on-off circuit 7 of the motor-variator 4, as well as an analog pressure sensor 6 controlling the motor-variator 4 and a flow sensor 5 controlling the on-off circuit 7. Water supply systems.

Description

Motor pump unit with pressure and flow sensors.

  The present invention relates to the

  topompes, whether they are intended to be immersed in wells

  deep or in a borehole or serve on the surface.

  In either case, the depth reached can be very important, a few meters for the pumps of

  surface more than 150 meters in the boreholes.

  The height of the water in these wells and boreholes is very variable. It can go up to the surface in certain periods and go down to others, practically

  level of the strainer of the pump. These variations may

  come from different origins: fluctuation of the water table or flow of the pump higher than the supply of the

  drilling. In any case, this variation named flap

  sheet, poses difficulties in the operation of the submerged pump: discomfort of use and safety (risk of bursting of the apparatuses), because this pressure induced by the phenomenon of rise of tablecloth is added

  at the pressure given by the pump.

  This pressure variation is very damaging for the user, because it imposes the need to provide pipes to accept these pressure variations or to use fireworks to reduce the pressure to a value compatible with its installation, which in any case, is very expensive. In addition, the operation of a submerged pump generally requires a servo device ensuring the start and

  stopping the group according to the needs.

  To mitigate the effects of rising water

  in the drilling, different principles can be used.

  - The simplest, if the rise of the water table is not very important (a few meters to ten meters),

  is to provide an installation capable of supporting the over-

  pressure generated. This results in an additional cost of the installation and a lack of comfort at the level of

use.

  - For larger variations, it is pos-

  sible to mount a pressure regulator at the head of the borehole which, by means of a hydraulic device, maintains the pressure

  close to a predetermined value. The device becomes

  particularly expensive when the rates to be controlled are

  important. This device, using mechanical parts

  in motion in the fluid, presents risks of deterioration or malfunction in the presence of sand

in water.

  - Another solution still used is

  at the discharge of the pump a relief valve which opens when the pressure is exceeded, beyond a

  predefined point. This solution leads to a fall in

  installation (some of the water being returned to the

  drilling), resulting in significant energy expenditure.

  - It is possible to limit the pressure at the plant using a regulating device

  consisting of a pressure vessel installed on the refuel-

  It is associated with a regulation pressure switch. The pressure switch ensures that the pump is switched on and off

  needs. In this type of hydropneuma-

  the pump is stopped by a pressure switch as soon as

  that the predetermined pressure is reached, the restarting

  vice by the same pressure switch at a lower pressure than

pool.

  This device has three main disadvantages: 1. It requires a high capacity tank with

  buffer of air under pressure so as to restore automatically

  water, if necessary, to prevent

  damaging to the pump and which are due to the following operating mode: if the operating flow becomes lower than a minimum flow rate corresponding to a maximum pressure detected by the pressure switch and from which it stops the pump, the duration during which the pump stays at

  the stop is directly proportional to the volume of the

  see. If it is too weak, the pressure again very quickly falls below the start threshold, which creates

beats.

  2. It requires frequent control of the pressure switch set points and deflation of the air buffer. If the pressure switch setpoints get too close, beats will occur. If they are too far away, the pump will not stop. If the inflation pressure of the air supply, providing the pressure necessary for the expulsion of

  the reservoir water decreases, this translates into a decrease in

  the amount of water returned, which becomes insufficient

  health, while if the pressure increases too much, there is even

no more water supply.

  3. The pressure in the installation oscillates between two values, so that the user feels, even in normal operation, pressure variations which are

  unpleasant, especially in the showers.

  The most rational solution is to modify the characteristics of the pump according to different

  parameters: (pressure, level, flow).

  To modify the characteristics of the pump, it suffices to vary its speed of rotation; for this, the motor is powered by an electronic device for changing either the frequency of the current (in the case of a frequency variation) or the supply voltage (in the case of a dimmer). To do this, a pressure sensor

  analogue (whose output signal varies proportionally

  pressure) detects the pressure in the

  pump back up and compare it to a set point.

  In the case where the value recorded by the sensor is different from the reference value, a processing circuit says

  P I D changes the speed of the motor, in order to return permanently

  nence to the reference setpoint. In this principle, it is

  uses standard devices (frequency converter)

  quence, analogue sensor, measuring unit P I D) but

  which are very expensive and require a great deal of

  tence because they are difficult to adjust.

  The invention overcomes these disadvantages by a motor pump unit which maintains the pressure in the installation at a sufficiently low value not to damage it even in

  the case of a rise in the water table, without over-

  installation, without loss of efficiency, without

  implement complicated and mobile equipment, difficult to

  ciles to operate and maintain and likely to

  cause flapping and pressure variations

  pleasant. The subject of the invention is therefore a pump unit

  comprising a discharge pipe pump, a motorcycle

  driver driving the pump and an on / off circuit of the motor-drive. According to the invention, there is provided an analog pressure sensor, detecting the pressure prevailing in the delivery pipe and controlling the motor-drive according to this pressure and a flow sensor, detecting

  a minimum threshold of flow of the fluid passing through the pipe-

  pressure and controlling the on-off circuit so as to put it in

becomes higher than this threshold.

  If the pressure in the discharge pipe increases, for example as a result of a rise in the water table, the analog pressure sensor controls the motor-drive accordingly and, by decreasing the speed of the

  rotation of the pump, tends to decrease the pressure.

  But, as the on-off circuit is controlled by the flow sensor, it suppresses the beats. In addition, the flow sensor and the analog pressure sensor do not have to be set to very tight setpoints. A drift in time of these devices only results in an insignificant displacement of the operating point of the

  pump set, without any inconvenience to the user.

  According to an advantageous embodiment, the cap-

  analogue pressure transmitter controls the variator by

  via a pressure-voltage or pressure transducer

  current, transforming the pressure characteristic into a transformed characteristic, into voltage or current, according to a prescribed transformation law, which is not

  proportional. In particular, the transforming characteristic

  mea corresponds to a pressure-flow characteristic of the pump set passing, firstly, by the point of the exploited part of the actual pressure-flow characteristic of the pump unit having the lowest pressure and, secondly, by the zero flow point having the same ordinate as the operating point of the actual pressure-flow characteristic of the pump unit having the higher pressure. Thanks to this transform, it is possible to overcome the actual pressure-flow curve of the pump, at least to carry out the control of the variable speed drive, and to substitute for this real curve an artificial curve which one

  conform to the best of what is desired for the operation.

  In particular, it is easy to give this trans-

  formed of the extreme ordinates of pressure value in the

  graph showing the variations in pressure

  flow, less distant than before, so that the user feels less pressure variations. It is also possible to give to the initial part of the curve

  characteristic from the y-axis a sensi-

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  parallel to the flow axis, so that at the beginning when a valve is opened, very quickly a large flow variation is obtained for almost the same pressure,

  whereas it was precisely here before that the variations

  pressures were most noticeable.

  According to one embodiment, the pressure sensor

  control via a transducer pres-

  voltage-voltage or pressure-current, called low-pressure transducer and transforming a pressure lower than a first

  threshold given in a temporary signal, the walking circuit

  stop so as to put it in the on position when the

  pressure becomes lower than this first given threshold.

  The pressure sensor can also control, by

  via a pressure-voltage or pressure transducer

  current-voltage said overpressure transducer, and transforming a pressure greater than a second given threshold into a permanent signal, the on-off circuit, so as to put it in the off position when the pressure becomes greater than the second given threshold , called overpressure threshold. We obtain

  thus a safety in case of accidental overpressure.

  According to a preferred embodiment, the output of the low-pressure transducer is connected to the first input of an OR gate whose other input is connected to the output of a flow-flow transducer or flow-rate of the flow sensor and whose output is connected to the first input of an OR.EX gate whose second input is connected to the output of the pressure transducer and whose output

  is connected to the on-off circuit. We thus associate

  the protection, in relation to an incident, and the

normal operating mode.

  Preferably, a timer is interposed between the output of the low pressure transducer and the first input of the OR gate so that the pump has time to provide a flow. In the opposite case, there is an anomaly and the on-off circuit of the pump stops it. There is also provided a timer interposed between the output of the transducer of the flow sensor and the second input of

  the OR gate, so as to ensure a certain duration of

  motor and to prevent beating. Even if the pressurized water reserve system is out of order, this

  timer limits the beats.

  In the attached drawing, given only for

For example:

  Figure 1 is a block diagram of the pump unit according to the invention; FIG. 2 is a graph showing the actual curve of the pump (curve I) and the transformed curve

  (curve II), the flows in m3 per hour being recorded in abs-

  and the total manometric heights in meters being plotted on the ordinate;

  FIG. 3 is a graph showing the variation

  the output voltage of the analog pressure sensor

  depending on the pressure in the discharge pipe; and

  FIG. 4 is a graph showing the variation

  the voltage at the output of the proportional band amplifier as a function of the pressure in the

discharge pipe.

  Referring to FIG. 1, a centrifugal pump

  has a discharge pipe 2 with

  buffer reservoir 3. Pump 1 is driven in rotation

  4. On the discharge pipe 2, a flow sensor 5 and an analog pressure sensor 6 are mounted. The motor-drive 5 is switched on or off.

  stopping by an on-off circuit 7.

  The analog pressure sensor 6 is connected to a proportional band amplifier 8 by a conductor 9, to a low pressure transducer 10, via a conductor 11, and to a pressure transducer 12 by a

  13. The output of the proportional band amplifier

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  8 is connected by a conductor 14 to the motor-drive unit 4. The output of the low-pressure transducer 10 is connected via a driver 15 and a timer

  16, at the first entrance 17 of an OR gate 18. The exit 19-

  The OR gate is connected by a conductor 20 to a first input 21 of an OR.EX gate 22. The output 23 of the OR.EX gate is connected, by a conductor 24, to the circuit.

on-off control 7.

  The flow sensor 5 comprises a transducer 25

  whose output is connected by a driver 26 and by a time

  porator 27 at the second entrance 28 of the OR gate 18.

  The output of the overpressure transducer 12 is connected by a conductor 29 to the second input 30 of the

door OR.EX 22.

  The operation of the pump unit according to the invention is now described, assuming first of all that the

  valve 31 mounted at the end of the pressure pipe

  2 is closed. The pressure prevailing in this delivery pipe 2 is equal to Ho on the graph of FIG.

2. Pump 1 is stopped.

  The valve 31 is opened. The capacity 3 of very small volume, for example of a volume of 1 liter, and which is intended simply to make sure that the outlet valve of the pump 1 is kept closed, returns a very low volume of water at the discharge pipe 2. The pressure in the discharge pipe 2 drops to the value H1

  in Figure 2 which constitutes a low pressure threshold. The cap-

  The pressure sensor 6 detects the pressure prevailing in the delivery pipe 2 and converts it into an electrical voltage, according to the curve of FIG. 3. By the conductor 11, this voltage is sent to the low-pressure transducer-10 which emits a signal limited in time by the timer 16 and entering the OR gate by the input 17. This signal sets the state 1, through the conductor 20, the input 21 of the OR gate. EX 22 and, like the entrance 30 of the door

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  OR.EX 22 is in the zero state, the output 23 of the OR.EX gate 22 is in state 1 and transmits the signal to the on-off circuit 7, by the driver 24. The on-off control circuit

  starting the motor-drive 4 and thus the pump 1.

  Water arrives in the discharge pipe 2. The flow sensor 5 detects that the flow exceeds a threshold

  given. By its transducer 25, the driver 26 and the time

  riser 27, it sends a signal to the entrance 28 of the door

  OR. This signal arrives, passing through the output 19, the

  20, the input 21, the output 23 and the driver 24,

  circuit 7. This maintains the motorcycle

  4 in operation, the signal arriving at the input 28

  of the OR gate 18 thus taking over the temporary signal

  at the entrance 17 of the OR gate 18. At the same time, the pressure sensor 6 detects a new, higher pressure in the discharge pipe 2. By the driver 9, it sends this voltage to the inlet of the the proportional band amplifier 8, which delivers in

  output a voltage according to the curve of Figure 4.

  Note that the curve in Figure 4 is the trans-

  formed of that of Figure 3, according to a law which is not proportional and in particular that it comprises an initial plate A between 0 and 3 bar and a plateau B terminal between 6 and 10 bar, with a proportional variation between the two trays. This transformed voltage is fed, by the conductor 14, to the variable speed drive 4 which thus does not see a voltage proportional to the pressure detected by the

  pressure sensor 6, but a transformed voltage corresponding to

  The drive controller 4 accordingly controls the rotational speed of the pump 1 and thus establishes an HF pressure in FIG. 2 corresponding to an operating point at which the pressure of the pump 1 is set. the intersection E of the transformed curve

  II and the load loss curve III of the installation.

  We now suppose that we close the tap

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  31. The pressure in the discharge pipe 2 increases along the curve E Ho in Figure 2. When we reach the intersection, in Figure 2, of the curve EHo and the minimum flow threshold represented by the right X, X 'in Figure 2 and detected by the flow sensor 5, it will send- through

  its transducer 25, by the driver 26 and by the timer

  27, a stop signal setting the input 28 of the OR gate 18 to the zero state, provided that the delay time defined by the timer 27 has elapsed and this in order to avoid beats. Since the temporary signal has disappeared and the input 17 is in the zero state, and the input 28 is in the zero state, the output of the OR gate is in the zero state. This state is transmitted to the input 21 of the gate OU.EX 22. As the same state prevails at the entrance of the gate 30, the zero state reigns at the exit 23 of the door OU.EX 22 and the

  on-off circuit 7 gives a stop command to the motorcycle

  4. The pump i stops. We found the initial state.

  We now assume that we are opening up the

  tap 31, but while the water table rose.

  It can be seen that because of the proportional band

  8, the pressure in the pressure pipe

  2, will always be governed by the transformed curve of the

  Figure 4 and can never exceed a prescribed limit.

  It is now assumed that it occurs accidentally

  There is also an overpressure in the discharge pipe 2 due for example to a water hammer. The pressure sensor 6 detects this pressure and converts it into a voltage which

  is conveyed by the driver 13 to the surge transducer

  pressure 12 which, by the conductor 29, puts the input 30 of the OR.EX 22 door to the state 1. If, at this moment, the pump 1 operates, the input 21 of the OU.EX gate 22 is also, in the state 1. As the two inputs 21 and 30 of the door OR.EX 22 are both in the state 1, the door 22 is not busy and controls, by the driver 24, the circuit-stop 7 so that it stops the

  motor drive 4, and therefore the pump 1.

  It is now assumed that, by accident, the pump 1 operates, while the valve 31 is open, but the pump does not deliver water. The flow sensor 5 finds that the flow rate, in the delivery pipe 2, is less than the only one defined by XX 'in FIG. 2. By the transducer, the conductor 26 and the timer 27, it puts the inlet 28 of the OR gate 18 in the zero state and therefore not valid

  the temporary start-up order issued by the trans-

  10. The input 21 of the OR.EX gate 22 is thus set to the zero state by the conductor 20. As the input 30 is also in the zero state since there is no overpressure, the door OU.EX 22 is not busy. The start-stop circuit 7 is not energized and gives a stop command to the motor-drive

4. Pump 1 stops.

Claims (8)

  1. Pump set including a pump (1)   discharge pipe (2), a motor-drive (4) driving   the pump (1) and an on-off circuit (7) of the motor-   variator (4), characterized by an analog pressure sensor (6) detecting the pressure in the   (2) and controlling the motovariator (4) in   this pressure, and by a flow sensor (5), detecting a minimum flow threshold of the fluid passing through the discharge pipe (2) and controlling the on-off circuit (7) when the flow becomes greater than this. threshold,   so as to put it in the running position.   2. Pump unit according to claim 1,   characterized in that the analog pressure sensor (6)   controls the motor-variator (4) via a trans-   driver (8) pressure-voltage or pressure-current, transform-   the characteristic of pressure and a characteristic transformed into voltage or current, according to a law of   prescribed transformation that is not proportional. -   3. Pump unit according to claim 2, characterized   characterized in that the transformed characteristic corresponds to a pressure-flow characteristic of the pump unit, passing on the one hand by the point of the exploited portion of the actual pressure-flow characteristic of the pump unit having the lowest pressure (H1) and, d on the other hand, by the point (Ho) of zero flow having the same ordinate as the point 13 2645213   of the exploited part of the actual pressure-   flow rate of the pump set with the highest pressure.   4. Pump unit according to Claim 1, 2   or 3, characterized in that the pressure sensor (6)   by a transducer (10) pressure-voltage or pressure-current, designated by low-pressure transducer and transforming a lower pressure to a first   threshold given in a temporary signal, the walking circuit   stop (7) so that it is in the on position when   the pressure becomes lower than this first given threshold.   5. Pump unit according to one of the claims   1 to 4, characterized in that the pressure sensor   control, via a transducer (12)   voltage-voltage or pressure-current, designated by overpressure transducer and transforming a pressure greater than a second given threshold into a permanent signal, the on-off circuit (7) so as to put it in the off position   when the pressure becomes greater than this second given threshold.   6. Pump unit according to Claim 4,   characterized in that the output of the low transducer pres-   sion (10) is connected to the first input (17) of an OR gate (18) whose other input (28) is connected to the output of a transducer (25) flowcurrent or flow-voltage of the flow sensor (5), and whose output (19) is connected to the first input (21) of an OR.EX gate (22) whose second input (30) is connected to the output of the pressure transducer   (12) and whose output (23) is connected to the operating circuit. stop (7).   7. Pump set according to one of the claims   4 to 6, characterized by a timer (16) interposed between the output of the low pressure transducer (10) and the   first input (17) of the OR gate (18).   Group according to one of Claims 4 to 7,   characterized in that the pressure sensor controls, via a transducer (12) pressure-voltage or Z645213   pressure-current designated by pressure transducer, and transforming a pressure greater than a second given threshold into a permanent signal, the circuit, on-off (7) so as to put it in the off position when the pressure becomes greater than this second threshold given.