EP1477678B2 - Early detection of failures in pump valves - Google Patents

Abstract

Monitoring method in which the increased operating noise caused by back flow of the transport fluid in a leaky valve in the closed state is taken as a measure for the size of the leak. The effective signal is monitored over time and compared with a reference signal for a pump with intact valves. When there is a predetermined noise level difference or change in difference due to increased operating noise, an early fault detection indicator is triggered. The invention also relates to a corresponding device for method implementation.

Description

The invention relates to a method for monitoring and automatic early fault detection of the valves, in particular the suction and / or pressure valves, an oscillating positive displacement pump, in particular a diaphragm metering pump, according to the preamble of claim 1.

The invention also relates to an apparatus for carrying out this method according to the preamble of claim 8.

In the case of oscillating positive displacement pumps, but especially in the case of diaphragm metering pumps, the pump valves, in particular the suction and pressure valves, have a decisive influence on the pump function.

The suction and pressure valves are subject to constant wear, which has a negative effect on the pump capacity and on their dosing accuracy.

In practice, attempts have been made to avoid this problem by replacing the valves in good time from experience.

Nevertheless, it can not be avoided that valves fail prematurely. This causes unwanted consequential damage due to the then necessary immediate service interruption.

Out GB 2 314 412 A is already a method for state and performance evaluation of pumps of any type with the aid of acoustic measurements known. The ratio of current measurements to reference values is used as a measure of the performance of the pump. For this purpose, averaged sound levels and peak values are used during certain periods. In addition, additional measured values, such as the absorbed power, the delivery head and the pump speed, can be used.

However, this pump monitoring, which is described in a very general form, does not give any indication of the specific problem of early fault detection of pump valves in oscillating positive displacement pumps.

Out US 4 896 101 A and US 2002/0062682 A Furthermore, the monitoring of motorized devices or externally operated valves is known. However, this also gives no indication of the special problem of monitoring and automatic early fault detection of the valves, in particular the suction and / or pressure valves, an oscillating positive displacement pump, in particular a diaphragm pump.

The invention is therefore based on the object to eliminate the disadvantages described to provide a method and a device by which it is possible to monitor the valves of a pump of the generic type such that there is an automatic early fault detection of the valves, so that valve damage be recognized in time and a shutdown of the pump can be planned.

The features of the method for solving this problem according to the invention will become apparent from claim 1.

The invention also provides an apparatus provided for carrying out this method, the features of which are listed in claim 8

Advantageous embodiments of the method and the device according to the invention are listed in the respective dependent claims.

The inventive method is based on the essential idea to use the increased operating noise generated by a leaking valve due to the backflow of the conveying fluid in the closed valve state as a measure of the leakage of the valve. For this purpose, the generated effective signal level is continuously monitored and compared with a reference signal level formed by the operating sound of the intact-valve pump, and at a predetermined level deviation due to increased operating noise, an early fault indication is triggered. According to the invention, it is provided that both the effective signal level and the reference signal level are averaged over a predetermined period of time, that the one used during a fraction of the Pumpenhubzyklus as a predetermined averaging period and that further to form the average value of the respective signal level, a trigger signal at a defined time during the Pump stroke cycle is used.

The invention thus makes use of the effect in an advantageous manner that a certain background noise can be seen with an intact pump. At the same time, some discrete typical individual noises occur. These have various causes, such as the meshing in the reduction gear on the pump engine or the opening and closing noises of the valves.

On the other hand, due to the backflow of the conveying fluid in the closed valve state, leaking valves produce increased typical operating noise. These increased operating noise are dependent on the Rückströmmenge of the conveying fluid and are used according to the invention as a measure of the leakage of the valve.

For example, with a defective suction valve during the displacement phase, i. during the pressure stroke to detect an increased noise level, while with a defective pressure valve during the suction phase, i. During the suction stroke, an increased noise level occurs.

The suction and pressure valves used in the oscillating displacement pumps, in particular in the case of the diaphragm metering pumps in question, are usually either ball valves or plate valves or conical valves, which can be spring-loaded or pressure-controlled. Here, the demands placed on these valves are that they must open and close at exactly the right time and that they must be tight in the intended time.

The damage that may occur to such valves manifests itself either in notch leakage generated by one or more notches on the valve seat, causing local damage, or from a surface damage generating surface lobe. Here, the sealing edge of the valve seat is not punctually damaged by one or more notches, but over the entire circumference. In both cases, an increased flow noise occurs at the valve seat, resulting in u.a. can be explained by the coincidence of cavitation bubbles occurring.

According to the invention, the generated operating noise of the pump and thus also that of the valves is measured as structure-borne noise. This can be done in an embodiment of the invention by means of a structure-borne sound sensor or a microphone, but in particular by means of a vibration acceleration sensor, which preferably operates on the piezoelectric compression principle and may have an integrated charge amplifier.

According to the invention, the generated structure-borne noise at the pump head, in particular at a central point thereof, can be measured. Instead, it is also possible to measure the generated structure-borne sound at or near the relevant valve. This may be the suction and / or pressure valve, in addition, however, also provided on the pump body further hydraulic valves, which serve to supplement the leak or the removal of excess hydraulic fluid.

For carrying out the inventively provided comparison formation between RMS signal level and reference signal level, as set forth, both the reference signal level formed by the operating noise of the pump with intact valves and the valve formed by the increased operating noise of the valve with leaking valves RMS signal level over a predetermined period of time averaged. In this case, the one used during a fraction of the pump stroke cycle as the predetermined averaging period. In this case, the evaluation of the signals takes place within a defined time window in the stroke cycle. For this purpose, according to the invention, a trigger signal is used, which is generated at a defined point in time of the pump lifting cycle. This can e.g. take place in the suction stroke end position of the piston. The trigger signal advantageously does not have to meet very high accuracy requirements. For example, an accuracy of +/- 5 ° crank angle. In this case, the generated structure-borne sound signal during the displacement phase (pressure stroke) is detected and compared for monitoring the suction valve in a defined period. In contrast, the corresponding period in the intake phase (intake stroke) is used as the basis for the monitoring of the pressure valve.

The defined period of time may extend only for the sake of example for monitoring the pressure valve over a range of 90-160 ° of the crank angle, while for the monitoring of the suction valve such a defined period is sufficient, which extends over a range of 270-340 ° of the crank angle extends.

• daß Undichtigkeiten sowohl am Saugventil als auch am Druckventil genau unterschieden werden können,
• daß die Empfindlichkeit der Messung sehr hoch ist und
• daß störende Schallquellen, z.B. solche aus dem Antriebssystem, leicht ausgefiltert werden können, indem beispielsweise das Zeitfenster, innerhalb dessen die Messung erfolgte, entsprechend groß oder klein definiert wird.

The advantages of evaluating the signals within a defined time window in the pump stroke cycle include:

• that leaks can be accurately distinguished both at the suction valve and at the pressure valve,
• that the sensitivity of the measurement is very high and
• that disturbing sound sources, for example those from the drive system, can be easily filtered out by, for example, defining the time window within which the measurement took place correspondingly large or small.

According to the invention, the trigger signal can be generated in various ways, for example by means of a contactor mounted on the pump engine, by means of a corresponding scanning of the piston rod, by means of the detection of a characteristic signal in the structure-borne noise signal generated, for example due to the play envelope in the engine, and also on the basis of other characteristic signals. eg the respectively measured pressure in the air space of the hydraulic storage space or in the engine.

As reference signal level, that reference value is suitably taken, which is assigned to an intact valve. This reference value may be detected in a variety of ways, for example by measuring in good condition of the valve under operating conditions, by a selection of predefined values, e.g. from a matrix with defined values for different valve designs and operating conditions, from a map determination, i. a computational determination of valve data and operating data, such as delivery pressure, fluid, etc., and the like.

In the aforementioned method, in which both the reference signal level and the effective signal level are averaged over a certain period of time during a fraction of the pumping cycle, according to the invention, the mean value can be formed from a number of pump strokes. Thus, the automatic early failure detection method according to the invention is insensitive to short-term disturbances. This can e.g. be useful when polluted fluids are metered by the pump in question. By fluid particles that are inadvertently clamped between the valve seat and valve closing body, it comes with individual pump strokes to a fluid backflow, but because only briefly and temporarily occurring, should not be displayed as a fault.

A further embodiment of the method according to the invention can be that of a number of pump strokes before their further signal processing a certain number of pump strokes with extreme values or with implausible values are sorted out.

For example, it is merely an example that the signal values of 100 pump strokes can be detected, whereby three pump strokes with the highest as well as the lowest individual values are sorted out in each case. For further signal processing, the average value is then formed from the remaining 94 values.

So that not only a current valve error can be displayed, it is within the scope of the invention to store the errors that occur with a corresponding time specification in a memory or to report these errors to higher-level control systems. This is particularly advantageous when a valve leakage occurs only temporarily and the leakage is not due to wear, but e.g. caused by temporarily contaminated fluid.

In a further embodiment of the invention, it is provided that the structure-borne sound signal generated by the respective valve is amplified by means of valve internals. These are in particular fittings on the valve seat whose purpose is to be excited to vibrate due to the leakage flow back to achieve an amplification of the structure-borne sound signal.

In a development of the invention, it may be advantageous to evaluate only a defined frequency band of the measured signals in order to increase the distance to the general noise signal.

It is finally within the scope of the invention, individual measurement data, such. a game envelope in the engine, hide from the considered time window. In this case, the existence of an exact trigger signal is advantageous.

The inventively provided device for carrying out the described method is provided with a connected to a pump component measuring device which monitors the increased operating noise generated by a leaking valve due to the backflow of the conveying fluid in the closed valve state and measures as RMS signal level, and with a device connected to the measuring device which compares the RMS signal level with a reference signal level formed by the operating sound of the intact valve pump, and generates a Fault Report as Fault Early Detection at a predetermined level deviation or change.

Advantageously, the measuring device has at least one sensor for detecting the structure-borne noise generated by the operating noise of the pump. In this case, this structure-borne sound sensor may be a vibration acceleration sensor, preferably piezoelectrically operating.

In an embodiment of the invention, the measuring device can either be connected to the pump head, in particular at a central point thereof. Instead, it is also possible to have the measuring device directly on or near the pump valves, i. the suction and pressure valve and the other hydraulic valves to provide.

If desired, the generated structure-borne sound signal can be amplified by suitable internals in the valve seat according to the invention. For this purpose, a vibration device is provided, which is provided at or near the valve seat.

Such a vibration device may consist of at least one wing installed at an angle into the valve or else a membrane sheet metal ring which is installed in the valve seat.

Fig. 1

schematisch im Schnitt die Anwendung des Verfahrens sowie der Vorrichtung gemäß der Erfindung bei einer Membrandosierpumpe sowie bei einer Kolbenpumpe;

Fig. 2a

im Diagramm den Kolbenweg der Pumpe über der Zeit,

Fig. 2b

im Diagramm den zeitlichen Verlauf des Druckhubs sowie des Saughubs der Membrandosierpumpe;

Fig. 2c

den als Körperschallsignal gemessenen Referenzsignalpegel eines intakten Pumpenventils sowohl beim Druckhub als auch beim Saughub,

Fig. 2d

den Effektivsignalpegel bei einem defekten Saugventil und

Fig. 2e

bei einem defekten Druckventil;

Fig. 3a

den Referenzsignalpegel sowie den Effektivsignalpegel in zeitlicher Mittelung über mehrere Pumpenhübe und

Fig. 3b

in zeitlich begrenzter Mittelung, d.h. in einem definierten Zeitfenster innerhalb des Hubzyklus.

The invention will be explained in more detail below with reference to the drawing. Hereby show:

Fig. 1

schematically in section the application of the method and the device according to the invention in a diaphragm metering pump and in a piston pump;

Fig. 2a

in the diagram the piston stroke of the pump over time,

Fig. 2b

in the diagram, the time course of the pressure stroke and the suction stroke of the diaphragm metering pump;

Fig. 2c

the reference signal level of an intact pump valve measured as a structure-borne sound signal both during the pressure stroke and during the suction stroke,

Fig. 2d

the effective signal level at a defective suction valve and

Fig. 2e

at a defective pressure valve;

Fig. 3a

the reference signal level and the effective signal level in time averaging over several pump strokes and

Fig. 3b

in time-limited averaging, ie in a defined time window within the Hubzyklus.

As in Fig. 1 shown schematically, the method and apparatus according to the invention can be used both in a diaphragm metering pump 1 and in a piston pump 2 for use. In this case, it is important to carry out a fault early detection in the respective provided suction valves 3 and pressure valves 4, which are each configured in the illustrated embodiment as a pressure-controlled ball valves.

For this purpose, a measuring device 5 is provided which is connected to a central point of the pump cap 6 and that of a leaky valve 3 and 4 due to the backflow of the conveying fluid monitored in the closed valve state generated increased operating noise and measures as RMS signal level.

The measuring device 5 is designed for measuring the structure-borne noise generated in each case by the operating noise and has a corresponding sensor. This is in the illustrated embodiment, a piezoelectric vibration acceleration sensor.

Furthermore, a comparison device 7 is provided which compares the effective signal level supplied by the measuring device 5 via a signal line 8 with a reference signal level formed by the operating noise of the pump with intact valves 3 and 4 and generates a fault message as early fault detection at a predetermined level deviation or change ,

As in detail Fig. 2a - 2e As can be seen, the various diagrams show the characteristics of the diaphragm metering pump 1 according to FIG Fig. 1 , Here is in Fig. 2a the piston travel over time shown.

Fig. 2b In contrast, shows the pressure curve in the hydraulic chamber 9 of the pump 1, wherein clearly the characteristic curve of the pressure stroke carried out by the piston 10 and the suction stroke of the membrane 11 (s. Fig. 1 ) is recognizable.

How out Fig. 2c can be seen, the course of the operating noise generated by a pump 1 with intact valves 3 and 4, which is measured as structure-borne noise signal, designed in a typical manner, wherein the in Fig. 2c illustrated course represents the reference signal level. This represents typical noise peaks that are generated during the pressure stroke and suction stroke performed by the pump piston 10.

In contrast, shows Fig. 2d the structure-borne sound profile of a pump 1 with defective suction valve 3, which typically occurs during the pressure stroke carried out by the piston 10, since in this case the suction valve 3 no longer closes exactly due to the leak and thus allows an undesirable leakage flow into the intake.

In contrast, shows Fig. 2e This results, as shown, during the suction stroke of the piston 10, since the leaking pressure valve 4 no longer reliably closes and an undesirable backflow in the form of a leakage flow into the fluid space 12 of the pump. 1 allows.

Fig. 3a and 3b Finally, show the level profile of the measured structure-borne sound signal in averaged form, wherein in Fig. 3a the averaging period during several pump strokes, that is, several times during the pressure stroke and the suction stroke, is shown and the early fault detection can be detected due to an increased RMS signal level. In contrast, shows Fig. 3b the waveform at an averaging period, which extends only over a fraction of the pump stroke cycle, in the illustrated case during only a certain time of the suction stroke.

Claims (15)

1. Method for monitoring of and automatic early fault detection in the valves, in particular suction and/or pressure valves, of an oscillating displacement pump, in particular a diaphragm metering pump,
   characterised in that
   the increased operating noise generated by a leaky valve due to the back flow of the conveyed fluid in the closed state of the valve, measured as structure-borne sound, is used as a measure of the valve leakage in that the effective signal level generated, determined over a specified period of time, is continuously monitored and compared with a reference signal level formed from the operating noise of the pump with intact valves, also determined over a specified period of time, that the period elapsing during a fraction of the pump stroke cycle is used as a specified averaging period for the relevant signal level and that, in order to form the average value of the current signal level, a trigger signal is used at a defined point in time during the pump stroke cycle wherein, in the event of a pre-specified deviation or change in level, an early fault detection indication is triggered on the basis of an increased operating noise.
2. Method according to claim 1, characterised in that the operating noise of the pump and thus also the valves, measured as a structure-borne sound, is determined by means of at least one structure-borne sound sensor or microphone.
3. Method according to claim 2, characterised in that a vibration acceleration sensor is used as a structure-borne sound sensor.
4. Method according to one of the preceding claims, characterised in that the generated structure-borne sound is measured on the pump head, in particular at a central position thereon.
5. Method according to one of the claims 1 to 3, characterised in that the generated structure-borne sound is measured on or near the valves.
6. Method according to claim 1, characterised in that the trigger signal is generated by means of a contact sensor fitted to the pump drive.
7. Method according to one of the claims 2 to 6, characterised in that the structure-borne sound signal generated by the valve in question is amplified by means of valve fittings.
8. Device for carrying out the method according to one of the preceding claims,
   characterised by
   a measuring device (5) connected to a pump component which monitors the increased operating noise generated by a leaky valve (3 and 4) due to the back flow of the conveyed fluid in the closed state of the valve and measures this as an effective signal level, and
   a comparison device (7), connected with the measuring device (5), which compares an effective signal level, determined over a specified period of time, with a reference signal level formed from the operating noise of the pump with intact valve (3 or 4), also determined over a specified period of time, and in the event of a pre-specified deviation or change in level generates a fault message as an early fault detection indication.
9. Device according to claim 8, characterised in that the measuring device (5) has at least one sensor for measuring the structure-borne sounds generated by the operating noise of the pump (1 or 2).
10. Device according to claim 9, characterised in that the structure-borne sound sensor is a vibration acceleration sensor (5).
11. Device according to one of the claims 8 - 10, characterised in that the measuring device (5) is attached to the pump head (6), in particular at a central position thereon.
12. Device according to one of the claims 8 - 10, characterised in that the measuring device (5) is provided on or near the pump valves (3, 4).
13. Device according to one of the claims 9 - 12, characterised in that in order to amplify the generated structure-borne sound signals the pump valve (3, 4) which is to be monitored is equipped with a vibrating device which is provided on or near the valve seat.
14. Device according to claim 13, characterised in that the vibrating device consists of at least one vane installed obliquely in the valve (3 or 4).
15. Device according to claim 13, characterised in that the vibrating device is a metal diaphragm ring.

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