DE102021102991B3 - Method of operating a hydropneumatic bladder accumulator - Google Patents

Abstract

Shown and described is a method for operating a hydropneumatic bladder accumulator with a pressure vessel (1), which has a bladder (2), an oil inlet (3), a gas inlet (4) and a pressure sensor (5), at least one temperature sensor (6) and Evaluation units (7, 11) for pressure and temperature. According to the invention, the temperature is measured at at least one other point with an additional temperature sensor (9) and a pressure profile over time in the bladder accumulator is recorded and compared with setpoint values, with an envelope curve being specified for the setpoint values, which is calculated using the temperature difference between the two temperature sensors (6th , 9) is formed, and the detected pressure profile is compared with the specified envelope curve during operation and an alarm signal is generated if the specified values are exceeded.

Description

The invention relates to a method for operating a hydropneumatic bladder accumulator.

A bladder accumulator is understood to mean a special hydropneumatic accumulator in which a flexible bladder acts as a separating element between a compressible gas cushion and a flowable medium, also referred to as an operating liquid. Pressure media in hydraulic systems such as hydraulic oil or other pressure fluids, but also lubricants or coolants can be considered as operating fluids.

The accumulators consist of a pressure vessel and the above-mentioned accumulator bladder as well as the fittings required for the connections on the gas and medium side.

Such hydraulic accumulators are offered by most well-known hydraulic manufacturers.

the DE 10 2009 010 775 A1 describes a hydraulic accumulator for accommodating at least a partial volume of a pressurized liquid, the hydraulic accumulator having a housing with at least one connection point to a hydraulic device, such as a hydraulic circuit. A data memory is part of the hydraulic accumulator and can be read out by means of a reading and/or writing device arranged outside of the hydraulic accumulator.

In one embodiment, a separating element is arranged in the housing of the hydraulic accumulator, separating two working chambers from one another. The data memory can have a sensor for detecting the pressure and/or the temperature. In the case of a pressure sensor, the pressure in the gas space can be determined and a warning signal can be sent to the assigned reading and/or writing device or a control device if the pressure falls below and/or exceeds a definable value.

the DE 10 2011 100 532 A1 describes, among other things, a bladder accumulator in which the transfer of at least one medium via the separating device into the other medium space should be detectable. A measuring device used for leak testing should have at least one sensor arranged on the gas side.

In addition to thermal sensors for determining thermal conductivity, optical measuring methods such as scattered light measurements or determining luminescence, measuring electrical conductivity, dielectric properties, chemical or physical measuring methods such as measuring the vibration behavior of the medium are also proposed.

The sometimes enormous measurement effort and the adjustments to the medium, d. H. the fuel.

Furthermore, from the WO 0208612 A1 a method for measuring the gas pressure in gas spring or gas storage balls is known. To determine the gas pressure, the temperature of the sphere shell is measured and the actual value determined is compared with its target value and any deviation is displayed. Deviations from the target values should be detectable by measuring the temperature of the ball shell with reference to the stored measurement data of the various operating states of the gas spring or gas storage balls.

From the DE 102009032859 A1 It is known that in order to determine a wear variable or a remaining service life of a hydraulic accumulator, measured values of a pressure in the hydraulic accumulator are recorded by means of a sensor unit. A wear variable function is stored in a memory, which assigns a wear value to a specific time profile of a plurality of measured values. A computing unit determines a wear variable or a remaining service life of the hydraulic accumulator using the determined measured values of the pressure and the wear variable function.

From the post-published DE 102020104040 B3 a method for operating a hydropneumatic bladder accumulator with a pressure vessel is known, which has a bladder, an oil inlet, a gas inlet and a pressure sensor, at least one temperature sensor and evaluation units for pressure and temperature, the temperature being measured at at least one other point with another temperature sensor is recorded, a pressure profile over time in the bladder accumulator is recorded and compared with setpoint values, and a temperature difference is formed between the two temperature sensors.

From the DE 10 2007 059 400 A1 a method for operating a hydropneumatic pressure accumulator is known, in which several preload pressure values are determined from a recorded liquid pressure curve over time and these are compared with a tolerance range, which is formed using the measured liquid temperature and the measured ambient temperature.

From the EP 2 647 849 A2 is a method of operating a hydropneumatic blower memory, in which temperature values are recorded by means of three different temperature sensors.

The object of the invention is to more precisely determine when a bladder accumulator is in operation when a good range is exceeded and thus possible damage to the accumulator bladder, and to improve the alarming associated therewith.

The object is achieved by a method having the features of claim 1. Advantageous refinements of the invention are specified in the dependent claims.

The essential idea of the invention consists in using pressure and/or temperature sensors that are often already present and arranging and evaluating them in such a way that damage, in particular fatigue of the bladder, can be detected by an evaluation unit connected to the sensors.

At least one pressure sensor and at least two, preferably three, temperature sensors are provided for this purpose. According to the invention, the pressure sensor is arranged either on the gas side or on the media side (oil side). A first temperature sensor is on a fitting and the other or the other two temperature sensor(s) is/are arranged at different heights on or in the bladder accumulator. The medium pressure and/or the gas pressure, the medium temperature and a temperature difference are determined in the area of the bladder, the evaluation being carried out by comparing them with setpoint values.

According to the invention, the target values of the permissible pressure profile are specified by an envelope curve, and the recorded pressure profile is compared with the specified envelope curve during operation. The envelope curve is determined in advance in a learning phase. The temperature prevailing at this point in time and the temperature difference between the at least two temperature sensors are also used to form the envelope curve. Thanks to the envelope curve, it is now possible to define an exact threshold value at any point in time, despite the very dynamic pressure curve, which separates the good range from the bad range, so that when this threshold value is exceeded, i.e. in the event of damage or a possible failure of the bladder accumulator , a secure alarm is possible.

The failure of a pressure accumulator makes e.g. noticeable by the fact that in a specific pressure range the necessary amount of liquid can no longer be absorbed or dispensed, with the failure often being caused by an incorrect gas pressure. Thus, failures can be avoided through permanent static and dynamic monitoring of the filling pressure and temperature and the service life of the system can be extended through predictive monitoring and the associated maintenance (predictive maintenance).

Since the statically measured pressure only indicates whether the inflation pressure is within a permitted range, dynamic pressure monitoring can provide information on changes in the bladder, see 3 .

However, in contrast to a piston accumulator, failures in a bladder accumulator usually occur spontaneously when the bladder bursts. To what extent the bursting of the bubble is noticeable through gas or liquid leaks remains to be seen. In any case, the filling pressure drops spontaneously.

Another indication of the change in the bladder are temperature differences, in particular between the gas or oil inlet and the container or in the bladder. Therefore, at least two, preferably three, continuously evaluated temperature sensors arranged according to the invention are proposed in order to detect a slowly changing temperature behavior (predictive maintenance).

1. 1. Erfassung der Anzahl der zyklischen Druckveränderungen (Zyklen)
2. 2. Erfassung der Zeit zwischen den einzelnen Zyklen
3. 3. Messung der Temperatur am Einlass, in der Mitte und am oberen Ende des Speichers
4. 4. Statische Druckmessung, Prüfung, ob sich der Druck im Soll-Bereich befindet
5. 5. Dynamische Druckmessung zur Erfassung der Zeit zwischen den einzelnen Zyklen
6. 6. Dynamische Druckmessung zur Erkennung von Veränderungen an der Blase.

The following diagnostic concept is suggested for a cyclically operated bladder accumulator:

1. 1. Recording the number of cyclic pressure changes (cycles)
2. 2. Recording the time between each cycle
3. 3. Measurement of temperature at the inlet, middle and top of the reservoir
4. 4. Static pressure measurement, checking whether the pressure is within the target range
5. 5. Dynamic pressure measurement to record the time between each cycle
6. 6. Dynamic pressure measurement to detect changes in the bladder.

The specified measuring system can be easily integrated into an existing condition monitoring system of a printing installation, for example a machine.

Other advantages of the invention are that already existing pressure sensors or temperature sensors are used and the proposed additional temperature sensors are easy and can be mounted on/in the housing of the pressure vessel without media contact.

A separate evaluation unit is usually not necessary because existing control units can usually be used. The invention thus permits cost-effective monitoring of the bubble accumulator mentioned, which serves to improve interference immunity. Remote monitoring via a local network or the Internet is also possible.

The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

• 1 einen erfindungsgemäßen Blasenspeicher in teilweise geschnittener Darstellung;
• 2 eine Auswahl der benötigten Druck- und Temperatursensoren;
• 3 typische Druckverläufe mit intakter Blase und ohne (bzw. mit geplatzter) Blase;
• 4 die Druckverläufe aus 3 übereinandergelegt und um eine Hüllkurve ergänzt;
• 5 die mit den Sensoren aus 2 verbundenen Auswerteeinheiten.

They show schematically:

• 1 a bladder accumulator according to the invention in a partially sectioned view;
• 2 a selection of the required pressure and temperature sensors;
• 3 typical pressure curves with an intact bladder and without (or with a burst) bladder;
• 4 the pressure curves 3 superimposed and supplemented by an envelope;
• 5 the ones with the sensors off 2 connected evaluation units.

In the following description of the preferred embodiments, the same reference symbols designate the same or comparable components.

the 1 shows a bladder accumulator according to the invention with a pressure vessel 1, which has a (gas) bladder 2, an oil inlet 3, a gas inlet 4 and a pressure sensor 5, a first temperature sensor 6 and two further temperature sensors 8 and 9. The gas inlet 4 has a gas valve 15 covered by a protective cap 14 . It is pointed out that a pressure measurement can also be carried out here.

According to the invention, the arrangement is designed to measure not only the pressure and the temperature at the media inlet 3 but also the temperature at at least two points, in the middle and at the upper end of the reservoir, and to evaluation units 7 for the pressure and 11 for the pressure, which are not shown to various temperature measuring points. This arrangement according to the invention can be implemented inexpensively and is easy to assemble.

the 2 shows the necessary sensors. Three temperature sensors of the type PT100 and one pressure sensor PT5301 from the applicant are shown. Of course, similar sensors from other manufacturers can also be used. Converters marked 10 (PT100 - temperature sensor to 4-20 mA) are required for the three PT100 temperature sensors.

3 shows typical pressure curves with an intact and without or with a burst bladder. As you can easily see, a burst bubble is easily recognizable from the pressure curve. However, damage to the bladder, leaks and material fatigue should be detected at an early stage (predictive maintenance).

In 4 the pressure curves are off 3 shown superimposed and supplemented by an envelope according to the invention, which was determined in advance in a training phase. The temperature prevailing at this point in time and the temperature difference between the temperature sensors 6, 8, 9 are also used to form the envelope curve. The envelope curve defines the good range of the pressure curve with an intact bladder. Should the bubble burst, it would end 3 set well-known sawtooth-like waveform, as in the front area of 4 is indicated. Thanks to the envelope curve, it is now possible to define an exact threshold value at any point in time, despite the very dynamic pressure curve, which separates the good range from the bad range in the event of a gradual deterioration due to leaks or material fatigue, a reliable alarm is possible. This is indicated as an example at the two points marked "bad area / alarm". Here the pressure signal resulting from a burst bubble is outside the envelope curve and thus outside the acceptable range.

5 shows the one with the sensors from the 2 evaluation units to be connected. The signals of the pressure sensor 5 are evaluated by a diagnostic unit for vibration sensors of the type VSE100 of the applicant, denoted by 7 . The signals from the three temperature sensors are fed to an AS-Interface control cabinet module of the type AC3222, designated 11, by the applicant. An AS-Interface power supply of the type AC1258 from the applicant is used as the power supply 13 .

The evaluation units 7 and 11 are connected to an IO-Link master with an AL1920 Ethernet/IP interface from the applicant. It is denoted by 12 and is used for communication with the outside world, in particular with higher-level control units. The wiring familiar to those skilled in the art is not shown explicitly.

Since this arrangement is readily apparent to those skilled in the art, the explanation can be brief being held. The evaluation units 7 and/or 11 contain sets of parameters for the sensors and the software required for their evaluation and for carrying out the evaluation method according to the invention, with the evaluation also being able to take place in a higher-level control and evaluation unit.

Reference List

1

pressure vessel

2

bubble (gas bubble)

3

Oil inlet / media inlet

4

gas inlet

5

Pressure sensor, for example a PT5301 from the applicant

6

First temperature sensor (for the medium), e.g. a PT100

7

evaluation unit, e.g. B a VSE 100 of the applicant for up to 6 sensors

8th

Second temperature sensor (for the gas bubble), e.g. a PT100

9

Third temperature sensor (for the gas bubble), e.g. a PT100

10

Converter PT100 - temperature sensor to 4-20 mA (3x)

11

Control cabinet, for example an AS-Interface control cabinet module AC3222

12

Ethernet switch, e.g. B. an IO-Link master with Ehernet/IP interface AL1920

13

Power pack, for example an AS-Interface power supply AC1258

14

graduation cap

15

gas valve

Claims (5)

Method for operating a hydropneumatic bladder accumulator with a pressure vessel (1) which has a bladder (2), an oil inlet (3), a gas inlet (4) and a pressure sensor (5), at least one temperature sensor (6) and evaluation units (7, 11 ) for pressure and temperature, wherein the temperature is measured at at least one other point with an additional temperature sensor (9) and a pressure profile over time in the bladder accumulator is recorded and compared with setpoint values, An envelope curve is specified for the setpoint values, which is formed with the help of the temperature difference between the two temperature sensors (6, 9), and the recorded pressure profile is compared with the specified envelope curve during operation and an alarm signal is generated if the specified values are exceeded. procedure after claim 1 , characterized in that the temperature is measured at a third point with a third temperature sensor (8) and that this temperature value is also included in the formation of the envelope. Procedure according to one of Claims 1 until 2 , characterized in that the oil pressure is detected and evaluated. Procedure according to one of Claims 1 until 2 , characterized in that the gas pressure is detected and evaluated. Procedure according to one of Claims 1 until 2 , characterized in that the difference between oil and gas pressure is detected and evaluated.

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