EP1759117B1 - Method and device for monitoring a flow of fluid delivered by a pump - Google Patents

Description

The invention relates to a method and a device for monitoring a pumped by a pump fluid flow.

In the promotion of a fluid through a pump, various problems may occur, so at constant speed of the motor driving the pump, the volume flow may be undesirably changed by pressure fluctuations in the system, for example fall off the slope of the system pressure. Furthermore, a number of errors can occur, such as an inadmissibly high cavitation, a flat increase in pressure at the beginning of the pressure stroke with a reduced flow rate due to air or gas inclusions, leaks to the outside and with respect to the inlet and outlet valve (suction or pressure valve). If such errors occur, they should either be corrected or at least a corresponding error message should be issued.

For fault detection, a system is known in which a pressure sensor is attached to the hydraulic space of a pump and measures the pressure in that space. This pressure is not representative of the pressure in the dosing, in particular due to the inherent stiffness of the membrane, which is particularly the case for double leak detection used for the case and also due to a possibly used return spring, without which in turn a safe suction is often not guaranteed. Criteria for the recognition of error functions should be only the mean suction and delivery pressure and the efficiency of the pump, which can only describe a faulty behavior very globally.

Further, it is known to provide a pressure sensor on the pressure side and to generate error signals when the system pressure falls below a lower predetermined value and exceeds an upper predetermined value. Control of the pump is just as impossible as precise error detection and fault identification.

It is known, for detecting poor operating states of a pump, to record the pressure progression over the piston stroke over time by continuously recording pressure values in constant time intervals during the piston progression and by examining the pressure change over time. The disadvantage is that this requires a known, fixed piston or motor movement, which requires a constant angular velocity.

The DE 197 38 844 A1 shows a method and apparatus for continuous electronic monitoring of

Functions of a metering pump, the device for this purpose, must have three sensors, namely a pressure sensor, a stroke length sensor and a pulse generator, since the pulse generator initiates the detection of measured values by detecting or detecting the start of the promotion during passage of the piston in the - dead - and the (maximum) conveying process should be determined by the stroke length sensor. During the pumping process, the pressure sensor records pressure values at constant time intervals. An analysis and a comparison with deficient operating states stored in an evaluation unit are carried out to determine possible errors. A disadvantage is the effort to be continuously monitored, especially in terms of device technology and the limitation of the use of the method and apparatus of the invention to constant angular velocities and thus conveyor operations.

The EP 1 437 509 A2 relates to a monitoring device for controlling the two cylinders of a piston pump by means of the pump pressure for a continuous metering in the chromatography. The pressure is measured in the piston chamber with the help of a pressure sensor and compared with nominal values. To drive a speed controlled electric motor is used.

The invention has for its object to provide a method and apparatus for monitoring a pumped by a pump fluid flow, by means of which while reducing the technical complexity and avoiding limitations, a reliable and accurate fault detection Identification in a wide range of applications is possible.

According to the invention, the object is achieved by a method of the type mentioned, which further has the characterizing features of claim 1. To achieve the above object, the invention further provides a device of the type mentioned above with the features of claim 21, which is characterized by at least one pressure sensor for continuous or quasi-continuous measurement of the pressure of the fluid at least in some areas of the stroke of the pump and through a comparison device for comparing the measured actual values of the pressure with target values. The latter can be specified for the respective pump type-specific as empirical values based on the knowledge of parameters of a pump and the use of the same, but also be obtained by a reference measurement from a faultless system.

According to a preferred embodiment, it is provided that the actual values of the pressure are assigned to positions of the piston or of the diaphragm of the pump and compared with the desired values corresponding to the same positions. The desired values of the pressure are preferably assigned in an indicator diagram of the piston position, which corresponds to a fault-free operation. Although an indicator diagram is generally also a pressure curve diagram, it specifically indicates the pressure curve over the piston path - ie for the pressure and suction strokes - as a closed line in the manner of a circular process. It is therefore much more universal than a pressure-time diagram, which in contrast is time- and speed-dependent. The indicator diagram may be as above either before installation the pump with the rest of the software are specified type specific and / or in each case new and the Situation to be generated accordingly. It is essential that the pressure curve is determined via the piston travel and does not respond to the time in any way and that a comparison with ideal target values for a trouble-free system, but not with poor operating conditions.

According to a preferred embodiment of the method according to the invention, it is provided that the desired values of the pressure at each measured time are determined from the travel diagram of an engine driving the pump. The driving diagram of the motor is the course of the revolution (steps / angles / reference points) of the same over time. In a speed-controlled motor, which is preferably used, this travel diagram is predetermined by the speed control. This is due to a rigid coupling or transmission of the rotational movement of the drive motor to the piston or the diaphragm by means of a gearbox, the position of these parts always known and thus given movement or speed of the piston, the speed may be different or can change. In this case, for example, the rotational speed during the compression stroke may be slower than during the suction stroke. The assignment of time and position is carried out by the engine and control of the same having drive system.

The engine is a step-by-step reversible motor such as a stepping motor, electronically commutated motor (EC motor) or the like. The movement of the motor is carried out step by step - control of the engine, so that the control of the engine always "knows" how the engine and thus the piston is. A sensor for instantaneous determination of the position of the piston over its entire path is not necessary and not provided. The drive system However, only for synchronization of the engine control have a certain position of the piston having synchronizing.

While an extremely preferred embodiment provides that the pressure in a metering chamber of the pump is measured, it can also be provided that the pressure in a supply line or in an outlet line to or from the metering chamber of the pump is measured. As a result, individual characteristic values can be determined. In a preferred embodiment, measurements take place in the dosing space and in a supply and / or the discharge line. As a result, a large number of values for determining a wide variety of errors can be detected, in some cases also redundantly.

In a further preferred embodiment of the method according to the invention, it can be provided that, when the pressure changes, in particular in the pressure stroke and / or in the pressure line, the drive speed of the pump is adjusted. As a result, a control of the pump in terms of a constant or desired flow rate is possible. Furthermore, a preferred embodiment of the invention provides that in the event of a deviation of the actual value from the pressure of the setpoint value, an error message is output.

According to a preferred embodiment, it is provided that the pressure profile is monitored at the end of the suction stroke and / or at the beginning of the pressure stroke, wherein in the case of persistence of the actual value of the pressure in the negative pressure region cavitation is present in both cases and reported, if necessary.

When monitoring the pressure curve in the compression phase of the pressure stroke can also be provided that the pressure gradient at a lower actual pressure gradient than Target pressure gradient an air / gas message is displayed in the dosing space.

Another preferred embodiment of the invention provides that the pressure curve in the area of the dead points of the pump is monitored, wherein in particular arranged at a faster pressure increase at the beginning of the pressure stroke and / or slow pressure reduction at the beginning of the suction stroke of a leakage in a downstream of the dosing Pressure valve is reported. In addition, at an early pressure drop at the end of the pressure stroke and / or a planographic pressure build-up at the beginning of the pressure stroke, a leakage of a suction valve arranged in the inflow of the dosing head is reported.

If the pressure is monitored during the pressure stroke, an error message may be output at the SETPOINT value of the pressure during the monitoring process. Such a pressure behavior, which indicates an unacceptably high system pressure, can occur, for example, when a pressure-side slide is inadmissibly closed.

In a further embodiment it can be provided that a leakage in the pressure line indicating leakage message is output at the target value of the pressure below the actual values.

The device according to the invention can be characterized in that a speed-controlled motor is provided for driving the pump, the angular position of which can in turn be used to determine the desired values for the pressure.

The comparison device is designed in particular in a computer, such as a PC, microcontroller or the like and can in particular control a motor control for a motor of the pump. In a further embodiment of the device according to the invention, input units for inputting input data, volume flow settings, evaluation strategies, maximum permissible pressure or the like as well as output units for outputting output data, such as error messages, pressure values, indicator diagram or the like may be provided. While in an extremely preferred embodiment, the pressure sensor is arranged in the dosing, further embodiments may provide that a pressure sensor in a supply line to the dosing and / or a pressure sensor is arranged in an output line from the dosing.

In the context of the invention, the comparison device compares steadily in critical phases of the pressure and suction stroke the instantaneous pressure curve (actual value) with that of a fault-free pressure curve (nominal value) and detects depending on the size of the deviation, whether the consequent dosage error is still tolerable is or is not and gives, if appropriate, a corresponding signal for the desired consequences. In this way, the numerous error causes occurring in practice can be detected and detected, such as cavitation, air bubbles, leaks and faults on the pressure and suction side. In addition, dosing errors can be compensated in a simple manner as a result of pressure fluctuations on the pressure side by adjusting the speed.

Fig. 1

ein schematisches Blockdiagramm einer erfindungsgemäßen Vorrichtung zur Überwachung eines von einer Pumpe geförderten Fluids mit einem im Dosierraum angeordneten Drucksensor;

Fig. 2a - 2f

weitere Anordnungen von einzelnen oder kombinierten Drucksensoren;

Fig. 3

ein Diagramm zur Veranschaulichung der Korrektur des Volumenstromes;

Fig. 4

ein eine Kavitation im Dosierraum anzeigendes Diagramm (durchgezogene Linie) gegen den normalen Druckverlauf (gestrichelte Linie);

Fig. 5

den Druckverlauf über den Hub bei Luft oder Gas im Förderraum;

Fig. 6

den Druckverlauf bei Leckage im stromabseitigen Druckventil;

Fig. 7

den Druckverlauf bei abfließender Leckage im Saugventil und/oder zum Außenraum; und

Fig. 8

ein Ablaufdiagramm zum Ablauf des erfindungsgemäßen Verfahrens.

Further advantages and features of the invention will become apparent from the claims and from the following description in which an embodiment of the invention with reference to the drawings is explained in detail. Showing:

Fig. 1

a schematic block diagram of an apparatus according to the invention for monitoring a pumped fluid from a pump with a pressure sensor arranged in the metering chamber;

Fig. 2a - 2f

further arrangements of individual or combined pressure sensors;

Fig. 3

a diagram illustrating the correction of the volume flow;

Fig. 4

a graph indicating cavitation in the dosing space (solid line) against the normal pressure curve (dashed line);

Fig. 5

the pressure curve over the stroke with air or gas in the delivery chamber;

Fig. 6

the pressure curve for leakage in the downstream pressure valve;

Fig. 7

the pressure curve when leakage occurs in the suction valve and / or to the outside; and

Fig. 8

a flowchart for the operation of the method according to the invention.

The in the Fig. 1 illustrated preferred embodiment of a device 1 according to the invention for monitoring a pumped by a pump fluid has a pump 2 with a metering chamber 3. The pump 2 is formed in the illustrated embodiment as a diaphragm pump and therefore has a membrane 4. The membrane 4 is of a Motor 5 driven and moved via the output shaft. In an inlet 7 to the dosing 3, a suction valve 8 is arranged in an outlet 9 from the metering chamber 3, a pressure valve.

The motor 5 is associated with a motor controller 11, by means of which on the one hand the motor operation is controlled and on the other hand in a speed-controlled motor, as well as a stepper motor, a motor position to a computer 12 (PC, microcontroller) reports, creating a travel diagram of the piston with is given known piston position or speed at any time, the controller so "white" at any time, where the piston is located. In the dosing a pressure sensor 13 is arranged, which is designed in particular as a pressure-voltage converter and the output signal via a line 14 is also supplied to the computer 12. The computer 12 is a comparison device for comparing actual values of the pressure measured by the pressure sensor 13 with the indicator diagram present from the motor position of the engine controller 11 in the context of a nominal pressure of a piston position ( Fig. 4-7 ) of the pump of certain desired values of the pressure and to effect an action in the event that both do not match. This action may consist, for example, in a speed adjustment via the control line 15 to the engine control 11 so as to adjust the engine speed. The computer 12 further input units 16 and output units 17 are assigned. About the input units, such as a keyboard, mass storage, etc. input data, such as flow adjustment, evaluation strategy, maximum allowable pressure or the like can be specified to the computer 12. Via the output units, such as screen, printer, loudspeaker, siren, optical path display, output data such as error messages, pressure values, indicator diagrams or the like can be output.

The Fig. 2a to 2f show further embodiments of the arrangement of pressure sensors for pressure detection. So is in the design of the Fig. 2a a pressure sensor 13a in the suction line 18, in the embodiment of Fig. 2b a pressure sensor 13b arranged in the pressure line 19 and in the embodiments of Fig. 2c to 2f Combinations of these pressure sensors 13, 13a, 13b are provided.

Thus, by means of a pressure sensor 13a on the suction side, the delayed start of a suction phase can be detected simply and precisely, while by means of a pressure sensor 13b on the pressure side, premature pressure reduction at the end of a pressure stroke as well as failure to reach the (output) system pressure can be detected simply and precisely In particular, in combination with a pressure sensor 13 provided in the metering chamber, the error detection can be improved.

The Fig. 3 shows the drop of the volume flow from Q ₁ to Q ₂ at constant speed n ₁ = n ₂ and system pressure increase from p ₁ to p ₂ . This drop in the volume flow is compensated by the computer 12 via the motor controller 11 by an increase to the speed n ₂ *> n ₁ so that the volume flow Q ₂ * = Q _{1 is kept} equal.

The Fig. 4 to 7 show indicator diagrams (Pressure graphs of the pressure across the stroke), where the stroke position with pressure 0 is the position of maximum size of the dosing chamber, in which the membrane in the Fig. 1 Thus, as far as possible by the engine is pulled to the left, while the stroke value 100% denotes the largely right position of the diaphragm and thus largely reduction of the dosing, then uses the suction stroke.

The Fig. 4 shows, as well as the Fig. 5 to 7 dashed the normal pressure curve in the dosing without any error, so a common indicator diagram. With a solid continuous line is in the Fig. 4 the pressure curve when cavitation occurs, ie the formation of vapor bubbles at low pressure, during the suction stroke in the liquid medium shown. The relative pressure during the suction stroke is negative and is below the pressure in a trouble-free case. Next, the pressure build-up over the normal course is much delayed, so it remains lower in the initial phase of the pressure stroke than during normal course. At the beginning of the printing stroke thus remains the actual value of the pressure in the negative pressure range, so that such a dosing error can be determined due to cavitation.

In the Fig. 5 is shown with a solid line the pressure curve when air or gas (without cavitation) occurs. It can be seen that, in contrast to cavitation, the increase in pressure takes place immediately at the beginning of the pressure stroke, but in the initial region of the pressure stroke, it is much flatter than during normal course. The occurrence of air or gas can thus be determined, in particular, by determining the actual gradient of the pressure profile with respect to the desired gradient, as a result of which it is possible to distinguish it from cavitation, since the gradient is substantially the same as in the normal pressure curve.

The Fig. 6 also shows in solid line the pressure curve for leaks in the pressure valve, so that the pressure valve does not close completely, so that at the beginning of the suction stroke, the pressure drop is much slower than normal course, as liquid through the pressure valve can flow back. In addition, the pressure increase at the beginning of the print stroke is faster or earlier than usual.

The Fig. 7 shows with continuous continuous line the diagram for an outflowing leakage in the suction valve and / or to the outside. Here, the leak is not only a slow increase in pressure, but the pressure can be lower overall than during normal course. In addition, premature pressure drop occurs at the end of the pressure stroke.

The sequence of a preferred embodiment of the method according to the invention is with the diagram of Fig. 8 shown. If the pressure remains at the end of the suction stroke and at the beginning of the pressure stroke in the vacuum region (steps A, B; Fig. 4 ), it is checked whether the present cavitation is still within a permissible range and / or the system pressure - in the further Druckhub phase - the predetermined pressure corresponds (steps C, D). If this is not the case, then an error signal is specified with regard to a false lift indicating a cavitation and / or a system pressure (step E).

If no cavitation has been detected, a pressure valve test is carried out, ie it is checked whether the pressure drop at the beginning of the suction stroke is too slow and the pressure build-up at the beginning of the pressure stroke is too fast. Furthermore, a system pressure test is also carried out by checking the pressures during the course of pressure and optionally suction stroke (step F; Fig. 6 ). If errors occur (step G), an error message regarding the faulty pressure valve (step H) also occurs. If no errors occur, a check for interfering gas bubbles in the dosing chamber takes place in the following (step I) Fig. 5 So, whether the gradient at the pressure build-up (and the pressure drop) is much flatter than that during normal operation. If this is the case (query J), then a corresponding error message (K).

If no impermissible cavitation, neither faulty pressure valve, nor gas bubbles and proper system pressure have been determined, then in the further (step L), a test for leakage in the suction valve and / or to the outside space corresponding to the Fig. 7 So, in effect, whether the pressure built up is too low, the pressure drop occurs at the end of the printing phase and / or a lesser pressure gradient occurs in the compression phase.

If this is also OK (query M), no action is required (block N), otherwise a leak message (P) will be issued.

LIST OF REFERENCE NUMBERS

1

contraption

2

pump

3

metering

4

membrane

5

engine

6

output shaft

7

inlet

8th

suction

9

outlet

10

pressure valve

11

motor control

12

comparator

13, 13a, 13b

pressure sensor

14

management

15

control line

16

input unit

17

output unit

18

suction

19

pressure line

20

Feedback of the motor position

Claims (28)

1. Method for monitoring a flow of fluid delivered by a pump, characterized in that piston positions are determined from the angular positions of a motor which drives the piston, in that the pressure of the fluid is measured continuously or quasicontinuously, at least in parts of the stroke of the pump, as actual values thrust against the piston position determined in this way, and is compared with desired values of the pressure thrusted against the piston position.
2. Method according to claim 1, wherein the desired pressure values are determined at each measured time point from the running diagram of a motor driving the pump.
3. Method according to claim 1 or 2, wherein the motor is speed-controlled.
4. Method according to one of the preceding claims, wherein the pressure is measured in a pump dosing chamber.
5. Method according to one of the preceding claims, wherein the pressure is measured in a pump suction line.
6. Method according to one of the preceding claims, wherein the pressure is measured in a pump pressure line.
7. Method according to one of the preceding claims, wherein the pump driving speed is adapted in the case of a change to the counterpressure.
8. Method according to one of the preceding claims, wherein a fault report is given if the actual value differs from the desired value for the pressure.
9. Method according to one of the preceding claims, wherein the pressure distribution at the end of the suction stroke is monitored.
10. Method according to claim 9, wherein cavitation is detected if the actual pressure value remains in the vacuum range.
11. Method according to one of the preceding claims, wherein the pressure distribution at the start of the pressure stroke is monitored.
12. Method according to claim 11, wherein a cavitation fault is indicated if the actual pressure value remains in the vacuum range.
13. Method according to claim 11, wherein a report indicating air/gas in the dosing chamber is given when the actual pressure gradient is lower than desired pressure gradients.
14. Method according to one of the preceding claims, wherein the pressure distribution in the vicinity of pump dead points is monitored.
15. Method according to claim 14, wherein in the case of a faster pressure rise at the start of the pressure stroke and/or a slow pressure drop at the start of the suction stroke a leak in a pressure valve positioned downstream of the dosing head is reported.
16. Method according to claim 14, wherein in the case of a premature pressure drop at the end of the pressure stroke and/or a flat compression line (pressure rise at the start of the pressure stroke) an outflowing leak of the suction valve located in the dosing head inflow and/or a leak to the exterior is reported.
17. Method according to one of the preceding claims, wherein the pressure during the pressure stroke is monitored.
18. Method according to claim 17, wherein a fault report is given if the actual values exceed the desired pressure value.
19. Method according to claim 17, wherein in the case of actual values dropping below the desired pressure value, a leak report indicating a leak in the pressure line is given.
20. Device for monitoring a flow of fluid delivered by a pump, characterized by a device for determining the piston positions from the angular positions of a motor which drives the piston, by at least one pressure sensor (13, 13a, 13b) for continuously or quasi-continuously measuring the pressure of the fluid thrust against the piston position of the pump (2) determined in this way, at least in parts of the stroke thereof, and by a comparison device (12) for comparing the measured actual values of the pressure with desired values thrust against the piston position.
21. Device according to claim 20, wherein a speedregulated motor (5) is provided for driving pump (2).
22. Device according to one of the claims 20 or 21, wherein the comparator (12) is constructed in a computer (PC, microcontroller).
23. Device according to one of the claims 20 to 22, wherein the comparator (12) is optionally also constructed for controlling a motor control (11) for a motor (5) of pump (2).
24. Device according to one of the claims 20 to 23, wherein there is at least one input unit (16) for inputting input data.
25. Device according to one of the claims 20 to 24, wherein there is at least one output unit (17) for outputting output data.
26. Device according to one of the claims 20 to 25, wherein at least one pressure sensor (13) is located in the dosing chamber.
27. Device according to one of the claims 20 to 26, wherein at least one pressure sensor (13c) is located in a suction line.
28. Device according to one of the claims 20 to 27, wherein at least one pressure sensor (13b) is located in a pressure line.

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