METHOD FOR DETERMINING A REMAINING EMPTY VOLUME, METHOD FOR ON-SITE CALIBRATION OF A FILL LEVEL MEASURING DEVICE, AND ON-SITE CALIBRATION MODULE

Abstract

Disclosed is a method for determining a remaining empty volume in a container, comprising: measuring a first pressure initially prevailing in the container; feeding in a gaseous pressure-boosting medium through an inlet, into the container; measuring the increased second pressure; determining the pressure increase caused by the infeeding of the pressure-boosting medium; determining a volume of the pressure-boosting medium that has been fed into said container; measuring a temperature prevailing in the container; and determining the remaining empty volume on the basis of the pressure increase, the volume of the pressure-boosting medium, and the temperature. Disclosed also is a method for on-site calibration of a fill-level measuring device in which the volume of the medium in the container is determined on the basis of the method for determining a remaining empty volume, and an on-site calibration module.

Claims

1-16. (canceled)

17. A method for determining a remaining empty volume in a container, wherein the container is embodied to receive a process medium and to be closed pressure-tight, and wherein the remaining empty volume is a remaining volume of the container which can be assumed by a medium, the method comprising: measuring a first pressure initially present in the container); flowing a gaseous pressure-boosting medium through an inlet into the container, wherein the pressure-boosting medium flowing into the container occupies the remaining empty volume and a pressure in the container is increased from the first pressure to a second pressure; measuring the second pressure; determining a pressure increase caused by the inflow of the pressure-boosting medium; determining a volume of the pressure-boosting medium flowing into the container; measuring a temperature present in the container; and determining the remaining empty volume on the basis of the pressure increase, the volume of the pressure-boosting medium, and the temperature.

18. The method according to claim 17, wherein the remaining empty volume is determined as follows from the pressure increase, the volume of the pressure-boosting medium, the temperature, and also from a specifiable reference temperature and a specifiable reference pressure: $V_{\mathrm{leer}}=V_{Mtest}.Math.\frac{T+Tn}{Tn}.Math.\frac{pn}{\Delta p+pn}$ wherein V.sub.leer is the remaining empty volume, V.sub.Mtest is the volume of the pressure-boosting medium, T is the temperature, Tn is the specifiable reference temperature, Δp is the pressure increase, and pn is the specifiable reference pressure.

19. The method according to claim 17, further comprising: continuously measuring a volumetric flow rate of the pressure-boosting medium during the inflow of the pressure-boosting medium through the inlet into the container by means of a flowmeter attached to the inlet; and determining the volume of the pressure-boosting medium flowing into the container by means of the measured volume flow rate during the inflow.

20. The method according to claim 17, further comprising: specifying a specifiable pressure and/or a specifiable target pressure increase; transmitting the first pressure to a control/evaluation unit configured to control a valve unit; measuring during the inflow the second pressure and transmitting the second pressure to the control/evaluation unit; and controlling the valve unit by the control/evaluation unit such that the pressure-boosting medium flows into the container until the second pressure reaches the specified pressure and/or until the pressure increase reaches the predetermined pressure increase.

21. The method according to claim 19, further comprising: specifying a specifiable target volume of the pressure-boosting medium; continuously delivering the determined volume of the inflowing pressure-boosting medium measured by the flowmeter to the control/evaluation unit during inflow; and controlling the valve unit by the control/evaluation unit such that the pressure-boosting medium flows into the container until the measured volume reaches the specifiable volume.

22. The method according to claim 17, wherein the steps of the method are carried out with a container in which there is the medium, so that the remaining empty volume for the container filled with the medium is determined, and wherein the volume of the medium in the container is determined using a difference between a total empty volume in the empty container that can be occupied by the medium, and the remaining empty volume for the container filled with medium:
Vmed=V_gesleer−V_leer wherein Vmed is the volume of the medium, V_gesleer is the total empty volume, and V_leer is the remaining empty volume.

23. The method according to claim 22, wherein the steps of the method are carried out with an empty container, and the remaining empty volume of the empty container determined in the process is determined as the total empty volume in the container which can be occupied by the medium.

24. A method for an on-site calibration of a fill-level measuring device which is designed to determine and/or monitor a fill level of a medium in a container, wherein the fill-level measuring device operates contactlessly, the method comprising: determining a total empty volume in the empty container that can be occupied by the medium; determining a remaining empty volume for the container; determining a volume of the medium in the container by subtracting the remaining empty volume from the total empty volume; measuring the fill level of the medium in the container by the fill-level measuring device; determining a volume of the medium in the container by the fill-level measuring device using an initially determined relation between the fill level measured with the fill-level measuring device and a volume of the medium in the container dependent on the fill level; and establishing, documenting, and/or displaying at least a difference between the volume of the medium in the container determined by the fill-level measuring device and the volume of the medium in the container determined using the method for determining the remaining empty volume.

25. The method according to claim 24, further comprising: adjusting the fill-level measuring device, wherein the measured value of the fill-level measuring device is adapted such that the volume of the medium in the container ascertained using the fill-level measuring device matches the volume of the medium in the container ascertained by the method for determining the remaining empty volume.

26. The method according to claim 24, wherein ambient air or a high-purity gas is used as the pressure-boosting medium.

27. The method according to claim 24, wherein during the inflow of the pressure-boosting medium, a pressurized gas cylinder or a compressed air system of a processing system is used in which the on-site method for calibrating a fill-level measuring device is carried out.

28. The method according to claim 24, wherein the on-site calibration of the fill-level measuring device takes place after a cleaning of the container with a cleaning medium, wherein the cleaning medium serves as the medium used in the on-site calibration, and wherein the container is steam-sterilized in particular after the on-site calibration of the fill-level measuring device.

29. An on-site calibration module for a fill-level measuring device which is designed for the on-site calibration of the fill-level measuring device, the module comprising: a flowmeter arranged on an inlet of a container; a pressure gauge designed to measure an initial pressure in the container and an increased second pressure in the container; a temperature measuring device designed to measure a temperature in the container; and a control/evaluation unit.

30. The on-site calibration module according to claim 29, wherein the pressure gauge and/or the temperature measuring device are arranged on the inlet of the container.

31. The on-site calibration module according to claim 29, wherein the on-site calibration module is designed as a mobile on-site calibration module which can be connected to a second valve unit arranged on the container.

32. The on-site calibration module according to claim 29, wherein the on-site calibration module is arranged on the container and fixedly connected to the container.

Description

[0063] The invention will be explained further with reference to the figures, which are not true-to-scale, wherein the same reference signs designate the same features. For reasons of clarity, or if it appears sensible for other reasons, previously-noted reference signs will not be repeated in the following figures. The following is shown:

[0064] FIG. 1: An embodiment of the method according to the invention for determining the remaining empty volume; and

[0065] FIG. 2: An embodiment of the method according to the invention for the on-site calibration of a fill-level measuring device, and an embodiment of the on-site calibration module according to the invention.

[0066] FIG. 1 shows an embodiment of the method according to the invention for determining the remaining empty volume V_leer. In this embodiment, the method is carried out with an empty container 1 in order to determine the entire total empty volume V_gesleer which is available in the empty container 1 for a medium and can be occupied by the medium. The total empty volume V_gesleer is ascertained once, for example initially before starting a fill-level measuring device 6 in a processing system (see FIG. 2). In this embodiment, further inlets and/or outlets of the container 1 through which for example a process medium PM or a cleaning medium RM can be supplied or discharged, and if applicable fittings present in the container 1, for example agitators or other field devices, are not shown in detail. In order to determine the remaining empty volume V_leer (in this special case, the total empty volume V_gesleer), a pressure-boosting medium Mtest flows into the container 1 via an inlet 2. The pressure-boosting medium Mtest is preferably a gaseous medium.

[0067] In this embodiment, the pressure-boosting medium Mtest is optionally purified ambient air which is introduced by means of a compressed air system 11 present in the processing system into the container 1 that is closed pressure-tight. Alternatively, for example a pressurized gas cylinder 10 containing the pressure-boosting medium Mtest is used for this. As the pressure-boosting medium Mtest flows into the container 1, the volumetric flow rate of the pressure-boosting medium Mtest through the inlet 2 is continuously determined. For this purpose, flowmeter 3, preferably a very precise Coriolis flowmeter, is used with which the volume V_Mtest of the entire pressure-boosting medium Mtest flowing into the container 1 is determined and transmitted to a control/evaluation unit 5. The control/evaluation unit 5 serves to evaluate the measured values transmitted by the measuring devices 3, 7, 8 and/or at least to regulate a valve unit 4. The valve unit 4 in this case comprises at least one valve which can be controlled by the control/evaluation unit 5 and is designed to shut off the inlet.

[0068] Before or during the inflow of the pressure-boosting medium Mtest into the container 1, the pressure p0 initially present in the container 1, or a pressure increase Δp caused by the inflow of the pressure-boosting medium Mtest and/or the increased pressure ph in the container 1, is ascertained. For this purpose, a pressure gauge 7 is arranged on the inlet 2 and transmits the measured values measured by it to the control/evaluation unit. In the case of pressure-controlled regulation, the pressure-boosting medium Mtest flows into the container 1 until a specifiable increased pressure phsoll is present in the container 1, or a specifiable pressure increase Δpsoll has been reached. When the target pressure increase Δpsoll is reached, the control/evaluation unit 5 controls the valve unit 4 in such a way that the inlet 2 is closed and no further pressure-boosting medium Mtest flows into the container 1. For this purpose, the valve unit 4 is arranged upstream of the flowmeter 3 with respect to the inflow direction of the pressure-boosting medium Mtest.

[0069] As an alternative to the pressure-controlled regulation of the method according to the invention presented here, volume-controlled regulation is possible. With the latter, the pressure-boosting medium Mtest flows in until the volume V_Mtest determined using the flowmeter 3 of the entire pressure-boosting medium Mtest flowing into the container 1 coincides with a specifiable volume.

[0070] At the same time, the temperature T present in the container is determined with a temperature measuring device 8 arranged on the inlet 2. Alternatively, the pressure gauge 7 and/or the temperature measuring device 8 can also be arranged in the container 1.

[0071] A reference pressure pn and a reference temperature Tn are then specified. The reference pressure pn and the reference temperature Tn are under normal conditions preferably an ambient pressure of 1013.25 hectopascals (hPa) or an ambient temperature of 273.15° Kelvin. The remaining empty volume V_leer is consequently ascertained from the measured volume V_Mtest of the pressure-boosting medium Mtest flowing into the container 1, the ascertained pressure increase Δp, and the measured temperature T and reference pressure pn or temperature Tn:

[00001]$V_{leer}=V_{Mtest}.Math.\frac{T+Tn}{Tn}.Math.\frac{pn}{\Delta p+pn}$

[0072] The total empty volume V_V_gesleer in the container is then determined as the remaining empty volume V_leer ascertained in this way with the empty container 1.

[0073] If medium (not shown) is now present in the container 1, the remaining empty volume in the container 1 is ascertained in just the same way as explained above using the method according to the invention. If there is medium in the container 1, the remaining empty volume V_leer will correspond to the negative of the volume of the medium Vmed in the container 1 up to a constant, the constant being the total empty volume V_V_gesleer described above. The volume of the medium Vmed in the container 1 can therefore be determined as follows.

Vmed=V_gesleer−V_leer

[0074] FIG. 2 shows how the method for determining the remaining empty volume is used in a method according to the invention for the on-site calibration of a fill-level measuring device 6 or in an on-site calibration module according to the invention.

[0075] In this exemplary embodiment, the fill-level measuring device 6 is the fill-level measuring device mentioned at the outset that is based on the transit time method and operates with microwaves, wherein the invention is in no way restricted to such fill-level measuring devices as mentioned above.

[0076] The fill-level measuring device 6 serves to determine and/or monitor the fill level L of a process medium PM in the container 1.

[0077] The fill-level measuring device is initially calibrated, i.e., displays a fill level L assumed to be correct. This fill level L is correlated in the prior art with the volume Vmed of the medium in the container 1, since this is an important control or regulating variable, for example in the production of, for example, pharmaceuticals. For this purpose, a known volume of a test medium, for example high-purity WFI water, is conducted into the container, generally when starting the fill-level measuring device 6. Based on the known volume of the test medium and the fill level L indicated by the fill-level measuring device 6, and within the context of so-called linearization, a calibration curve Vmed (1) is generated with which the fill level L indicated by the fill-level measuring device 6 is converted into the volume Vmed of the medium in the container 1 in a subsequent measuring mode. Optionally even within the context of this start-up, the volume Vmed of the test medium in the container 1 is determined, as already described, using the method for determining the remaining empty volume V_leer. The volume Vmed of the test medium in the container determined by the fill-level measuring device 6 is thereby matched, or the volume Vmed of the test medium determined using the method for determining the remaining empty volume V_leer is adapted in such a way that it coincides with the volume Vmed(L) indicated by the fill-level measuring device.

[0078] In order to now calibrate, verify and/or adjust the fill-level measuring device 6 after a measuring mode, for example at set, regular intervals, the method is used to determine the remaining empty volume V_leer. For this purpose, there can advantageously be medium in the container 1 and the fill-level measuring device 6 does not have to be removed; instead the pressure-boosting medium Mtest is introduced into the container 1 with medium therein, in this case cleaning medium RM.

[0079] The volume Vmed of the medium in the container 1 is now determined once, as already described, using the method for determining the remaining empty volume V_leer and is determined once with the fill-level measuring device 6, wherein the calibration curve Vmed(L) assumed to be constant is used for the conversion.

[0080] Given the comparison described above, a deviation between the volume Vmed 1 determined using the fill level L and the volume Vmed determined using the method for determining the remaining empty volume V_leer can be attributed to a drift of the fill-level measuring device 6.

[0081] To display at least the difference between the volume Vmed determined by the fill-level measuring device 6 and the volume Vmed ascertained by the method for determining the remaining empty volume V_leer, the on-site calibration module 12 optionally comprises display means, for example a display unit connected to the control/evaluation unit 5 such as a display. Alternatively, the display can also be on a separate, optionally mobile, terminal (for example a PC, a laptop, a smartphone, a tablet, data glasses, etc.) with which the control/evaluation unit 5 communicates by means of a communication network, in particular via an field bus from automation engineering and/or via Ethernet, wirelessly and/or wirelessly.

[0082] When the fill-level measuring device 6 is adjusted, it is additionally adapted in such a way that the indicated fill level L yields a volume Vmed(L) which corresponds to the volume Vmed of the medium in the container 1 ascertained by the method for determining the remaining empty volume V_leer.

[0083] The method for the on-site calibration of the fill-level measuring device 6 is preferably integrated into existing processes in the processing system so as to minimize processing system downtime. Since, in the aforementioned industries, the process must be interrupted for regular CIP cleaning of the containers 1 in any case after the production of a so-called batch, this is a preferred point in time for the subsequent on-site calibration of the fill-level measuring device 6. For this purpose, the method with the cleaning medium RM in the container 1 and used in CIP cleaning is employed as shown in FIG. 2. Since steam-sterilization of the container 1 often takes place here after CIP cleaning, there are also basically no restrictions on the pressure-boosting medium Mtest used for this. Of course, the use of another medium instead of the cleaning medium RM, in particular the process medium PM, is also possible within the scope of the method according to the invention. Depending on the type of process medium PM, restrictions on the type of pressure-boosting medium Mtest may then result.

[0084] An on-site calibration module 12 comprises the flowmeter 6, the pressure gauge 7, the temperature measuring device 8, the valve unit 5 and the control/evaluation unit 5. This is either fixedly connected to the container or, alternatively, can be connected via a second valve unit as a mobile on-site calibration module 12 to the container 1, for example to a second valve unit 9 attached to the container 1.

REFERENCE SIGNS AND SYMBOLS

[0085] 1 Container [0086] 2 Inlet [0087] 3 Flow-rate measuring device [0088] 4, 9 Valve unit, second valve unit [0089] 5 Control/evaluation unit [0090] 6 Fill-level measuring device [0091] 7 Pressure gauge [0092] 8 Temperature measuring device [0093] 10 Gas cylinder [0094] 11 Compressed air system [0095] 12 On-site calibration module [0096] V_leer Remaining empty volume [0097] V_gesleer Overall empty volume [0098] PW Process medium [0099] RM Cleaning medium [0100] Matest Pressure-boosting medium [0101] V_Mtest Volume of pressure-boosting medium [0102] V_Mtest_ Specifiable target volume [0103] Vmed Volume of medium in the container [0104] p0, ph First, second pressure [0105] Δp Pressure increase [0106] pn Specifiable reference pressure [0107] phsoll Specifiable target pressure [0108] Δpsoll Specifiable target pressure increase [0109] T Temperature [0110] Tn Specifiable reference temperature [0111] L Fill level [0112] Vmed(L), Vmed′(L′) Relation between volume and fill level