LIQUID SUPPLY SYSTEM

Abstract

A liquid supply system includes a suction lance (6) configured to be inserted into a liquid container (14) and at least one level sensor (10, 12) fixed on the lance (6) and configured to detect a liquid level (22) inside a liquid container (14). A control device (4) is connected to the level sensor (10, 12) and configured to determine a rate of change of the liquid level (22) detected by the at least one level sensor (10, 12) and to detect a lance removal if the rate of change reaches or exceeds a predefined threshold. A method for detecting the removal of a suction lance (6) from a liquid container (14) is provided.

Claims

1. Liquid supply system comprising: a suction lance configured to be inserted into a liquid container; at least one level sensor fixed on said lance and configured to detect a liquid level inside a liquid container; a control device connected to said level sensor and configured to determine a rate of change of the liquid level detected by said at least one level sensor and to detect a lance removal if a rate of change of the liquid level detected by said at least one level sensor reaches or exceeds a predefined threshold.

2. Liquid supply system according to claim 1, wherein said control device is configured such that said control device produces a lance removal signal when detecting the lance removal.

3. Liquid supply system according to claim 1, further comprising at least another level sensor, wherein: the at least two level sensors are fixed on said suction lance vertically distanced from each other; and the control device is configured to measure a time between a falling dry of the two sensors as the rate of change of the liquid level detected by said at least one level sensor.

4. Liquid supply system according to claim 3, wherein the control device is configured to detect the lance removal if the time between falling dry of the at least two level sensors is below a predefined threshold.

5. Liquid supply system according to claim 1 wherein the at least one level sensor is a single sensor configured to detect different liquid levels.

6. Liquid supply system according to claim 3, wherein the at least two level sensors are configured as liquid sensors detecting a dry state and a wet state.

7. Liquid supply system according to claim 1, wherein the at least one level sensor is a float switch.

8. Liquid supply system according to claim 1, further comprising a metering pump connected to said suction lance, wherein said control device is connected to or integrated into a pump control of the metering pump.

9. Liquid supply system according to claim 8, wherein said pump control is configured such that said pump control generates a lance removal signal if the lance removal is detected or inhibits a restart of the metering pump if the lance removal is detected or both generates a lance removal signal and inhibits a restart of the metering pump if the lance removal is detected.

10. Liquid supply system according to claim 9, wherein said pump control is configured such that for restart of the metering pump, after detection of a lance removal, the pump control requires a restart code.

11. Method for detecting the removal of a suction lance from a liquid container, wherein the suction lance comprises at least one level sensor fixed on said suction lance, the method comprising the steps of: determining a rate of change of the liquid level detected by said at least one level sensor; and detecting a lance removal if the rate of change of the liquid level detected reaches or exceeds a predefined threshold.

12. Method according to claim 11, wherein: the suction lance further comprises at least another level sensor; the at least two level sensors are fixed on the suction lance vertically distanced from one another; and the rate of change is determined based on a time between falling dry of the two sensors.

13. Method according to claim 11, wherein the at least one level sensor is a single sensor configured to detect different liquid levels.

14. Method according to claim 11, wherein the suction lance is part of a liquid supply system that further comprises a control device connected to said level sensor and configured to determine a rate of change of the liquid level detected by said at least one level sensor and to detect a lance removal if a rate of change of the liquid level detected by said at least one level sensor reaches or exceeds a predefined threshold.

15. Method according to claim 14, wherein said control device is configured such that said control device produces a lance removal signal when detecting the lance removal.

16. Method according to claim 14, wherein a metering pump is connected to the suction lance, wherein the control device is connected to or integrated into a pump control of the metering pump.

17. Method according to claim 14, wherein said pump control is configured such that said pump control generates a lance removal signal if the lance removal is detected or inhibits a restart of the metering pump if the lance removal is detected or both generates a lance removal signal and inhibits a restart of the metering pump if the lance removal is detected.

18. Liquid supply system comprising: a suction lance configured to be inserted into a liquid container; a level sensor device fixed on said lance and configured to detect a liquid level inside a liquid container; a control device connected to said level sensor device and configured to determine a rate of change of the liquid level detected by said level sensor device and to detect a lance removal if a rate of change of the liquid level detected by said level sensor device reaches or exceeds a predefined threshold.

19. Liquid supply system according to claim 18, wherein: the level sensor device comprises at least two level sensors fixed on said suction lance and distanced from each other; and the control device is configured to measure a time between a falling dry of the two sensors as a rate of change.

20. Liquid supply system according to claim 18, wherein the level sensor device is a single sensor configured to detect different liquid levels.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the drawings:

[0024] FIG. 1 is a schematic view showing a liquid supply system according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] Referring to the drawings, the shown liquid supply system comprises a metering pump 2 having a control device 4 for controlling the operation of the metering pump 2. The metering pump 2 is connected to a suction lance 6 via a suction line 8. On the suction lance 6 there are fixed two level sensors 10 and 12 (a level sensor device comprising at least one level sensor). The level sensors 10 and 12 are vertically distanced and the level sensor 10 is provided for generating an empty signal, whereas the higher level sensor 12 is arranged for generating a pre-empty signal. The level sensors 10 and 12 are connected to the control device 4 so that the control device 4 can receive and evaluate the sensor signals.

[0026] The suction lance 6 is inserted into a liquid container 14 for supplying a liquid like a chemical which is pumped or sucked by the metering pump 2. The liquid container 14 has an opening 16 through which the suction lance 6 is inserted. On the suction lance 16 there is arranged a closing element 18 which is attached to the opening 16 for closing the remaining part of the opening and fixing the suction lance 6 inside the liquid container 14, in particular in vertical direction. The lower free end 20 of the suction lance 16 in this position is arranged close to the bottom of the liquid container 14. In this free end 20 the suction lance 6 has a suction opening through which a liquid is sucked and feed to the metering pump 2. During operation of the metering pump 2 liquid is sucked out of the liquid container 14 so that the liquid level 22 decreases in the direction of the arrow A. When the liquid level 22 reaches the upper liquid sensor 12 the liquid sensor 12 gives a signal to the control device 4 which is the pre-empty signal. The control device 4 may signalize to an operator that the liquid container 14 becomes emptied soon. With the further decreasing of the liquid level 22 in direction A the liquid level 22, then, will reach the lower level sensor 10 when the liquid container 14 is emptied or substantially emptied and the signal generated by the level sensor 10 in response can be regarded as an empty signal. This signal is transferred to the control device 4 and the control device 4 can for example stop the operation of the metering pump 2 and signalize to an operator that the liquid container 14 has to be exchanged.

[0027] According to the invention the control device 4 is configured such that the control device 4 has a lance removal detection system. This may be realized by a respective software inside the control device 4. During normal operation the decreasing of the liquid level 22 takes a certain time, i.e. there is a certain time between the upper level sensor 22 falling dry and the lower level sensor 10 falling dry. If the suction lance 6 is removed out of the liquid container 14 in direction of arrow B the upper level sensor 12 will pass the liquid level 22 first and the lower level sensor 10 will pass the liquid level 22 later. This means also when removing the suction lance 6 the upper level sensor 12 falls dry first and the lower level sensor 10 falls dry later. However, the speed when removing the suction lance 6 out of the liquid container 14 is much faster than the speed with which the liquid level 22 decreases during normal operation. This means dB/dt is higher than dA/dt. This allows to detect the lance removal if the change rate of the liquid level 22 detected by the level sensors 10 and 12 is higher than a predefined threshold, i.e. if the time period between the signals generated by the upper level sensor 12 and the lower level sensor 10 showing that the sensors fall dry is smaller than a predefined threshold. For example the threshold may be ten seconds. Thus, if the time between a dry detection of the upper level sensor 12 and the lower level sensor 10 is below 10 seconds this is regarded as a removal of the lance 6 out of the liquid container 14.

[0028] The control device 4 may be configured such that in response of the lance removal detection the control device 4 starts an action for example stops the operation of the metering pump 2 or signals to an operator that the suction lance 6 has been removed from the liquid container 14. With this, for example, a change of the liquid container 14 can be detected. Furthermore, it can be detected if the suction lance 6 is removed from the liquid container 14 to open the opening 16, for example for refilling the liquid container 14. In certain applications if may be undesirable to refill the liquid container 14, for example to ensure a certain quality of the liquid supplied to the metering pump 2. For these solutions the described lance removal detection may be advantageous.

[0029] In case that the lance is removed after the liquid container has been emptied no lance removal can be detected by use of the two level sensors 10 and 12. Thus, the lance can be removed from the liquid container 14 without an alarm or any further action of the control device 4.

[0030] In this embodiment there are shown two level sensors 10 and 12 vertically distanced from one another. However, it would also be possible for the level sensor device to comprise a floating sensor which may be able to detect different liquid levels 22 and detect a change of the height of the liquid level 22 with a single sensor. For example a floating element may be coupled to a position sensor detecting the vertical position. Also by use of such a single level sensor it would be possible to detect the change rate of the height of the liquid level 22 to analyze whether the change is faster than a predefined threshold which cannot be achieved during normal operation of the metering pump 2 and thus indicates a lance removal.

[0031] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

LIST OF REFERENCE CHARACTERS

[0032] 2 metering pump [0033] 4 control device [0034] 6 suction lance [0035] 8 suction line [0036] 10, 12 level sensors [0037] 14 liquid container [0038] 16 opening [0039] 18 closing element [0040] 20 free end [0041] 22 liquid level [0042] A direction in which the liquid level decreases [0043] B lance removal direction