Automated detection of grease and oil contamination in the dosing unit of automatic vacuum sampling devices

Abstract

The invention relates to an automated detection of oil or grease contamination in the dosing unit of automatic sampling devices based on the vacuum principle.

Description

[0001] The invention relates to an additional device for the automatic sampling of liquids for the detection of fat or oil contained in the liquid, or similar components that can lead to disturbances in the sampling process.

[0002] The automatic sampling device for extracting liquids from deep sampling points using a vacuum system typically consists of the following parts: a control unit (1), a dosing unit (10), a vacuum pump (2), a discharge valve (7), and a suction hose (6). In most systems, the dosing unit (10) contains two cut-off electrodes (5) made of a conductive material. As soon as the liquid level in the dosing vessel (10) reaches these electrodes, this is detected via the conductivity of the aspirated liquid by these electrodes (5) and reported to the control unit (1), which then terminates the suction process. Since such devices are used in wastewater applications, malfunctions frequently occur when the cut-off electrodes become coated with oil or grease and can therefore no longer detect the liquid level in the dosing vessel (10).Since this oil or grease is usually located on the surface of the aspirated liquid, these electrodes (5) gradually become coated from the bottom up, causing the liquid to be drawn higher and higher into the dosing unit (10) with each subsequent sampling, until the electrodes can no longer detect it at all. This usually results in the liquid being drawn through the pump (2), potentially damaging it and other components in the sampling device. Consequently, the entire sample becomes worthless.

[0003] There are systems that detect the water in the dosing unit using capacitive sensors, or through a combination of conductivity electrodes and capacitive sensors. However, even these systems do not protect against malfunctions or damage.

[0004] A system that detects the presence of such substances early is desirable, so that a warning message can be issued or sampling can be stopped automatically.

[0005] Based on this prior art, the invention aims to automatically detect the presence of the aforementioned substances in the sample liquid and to initiate appropriate actions.

[0006] This problem is solved according to the invention by incorporating a second pair of cut-off electrodes with the features of claim 1. Further advantageous embodiments can be found in the related claims.

[0007] The basic idea of ​​the invention is to detect contamination early via a second pair of cut-off electrodes. In normal operation, the fill level in the dosing vessel is detected via the lower pair of electrodes, and the suction cycle is controlled accordingly. If this lower pair of electrodes gradually becomes coated with, for example, oil or grease, the fill level will rise until it is detected by these electrodes, at which point the second pair of electrodes is reached and the suction process is switched off. An error message is then sent and, if necessary, the dispensing program is stopped.

[0008] The invention is explained in more detail below with reference to four exemplary embodiments illustrated in the drawings. Further features of the invention will become apparent from the following description of the exemplary embodiments of the invention in conjunction with the claims and the accompanying drawings. The individual features of the invention can be implemented individually or in combination in different embodiments of the invention. The drawings show, in schematic representation: Fig. I a sampling device according to the invention for liquid samples with 2 pairs of electrodes, one of which has a distance decreasing upwards Fig. II a sampling device according to the invention for liquid samples with only 3 electrodes, one of which is installed at an angle Fig. III a sampling device according to the invention for liquid samples with only 3 electrodes, one of which is conically shaped Fig. IV a sampling device according to the invention for liquid samples with 2 electrode pairs Fig. V a sampling device according to the invention for liquid samples with only 3 electrodes Fig. VI a sampling device according to the invention with only one electrode pair and a float switch located above it Fig. VII a sampling device according to the invention with only one electrode pair and a capacitive sensor located above it Function:

[0009] In this automated sampling process, the sample liquid is drawn from the sampling point (9) through the suction hose (6) into the dosing vessel (10) after the drain valve (7) has been closed and the pump (2) has created a vacuum in the dosing unit (10). As soon as the sample liquid flows into the dosing unit (10) through the suction hose (6), the liquid level in this dosing unit (10) rises. As soon as this level reaches the electrode pairs (5) and (14), the sample liquid is detected by measuring the conductivity between the respective electrode pairs, and the suction process is terminated. Since the electrode pair (14) has a greater distance at its lower end than the electrode pair (5), the measured conductivity value will always be lower than the value of electrode pair (5).However, if the sample liquid contains oil, grease, or similar electrically insulating substances, the two electrode pairs (5) and (14) can gradually become coated from the bottom up, causing the liquid level in the dosing unit to rise continuously. This results in the measured conductivity values ​​of the two electrode pairs (5) and (14) becoming increasingly similar, as the distance between electrode pair (14) decreases towards the top. This allows the control unit to detect that the cutoff level in the dosing unit (10) is rising and therefore indicates contamination of the cutoff electrodes. A limit value can thus be set based on the change in the conductivity difference between the two electrode pairs (5) and (14), at which point a fault message is issued or the sampling program is interrupted.

[0010] Fig. Figure II shows a sampling device according to the invention as in Fig. I describe, but with only one electrode pair (5) and another, obliquely installed electrode (14). The function is the same as in Fig. I described, however, one of the electrodes (5) is the common electrode, via which the conductivity is measured in relation to the other electrode (5) and in relation to the obliquely installed electrode (14).

[0011] Fig. Figure III shows a sampling device according to the invention as in Fig. II, but with only one electrode pair (5) and another, conically shaped electrode (14). The function is the same as in Fig. I described, however, one of the electrodes (5) is the common electrode, via which the conductivity is measured in relation to the other electrode (5) and in relation to the conically shaped electrode (14).

[0012] Fig. Figure IV shows a sampling device according to the invention as shown in Figure IV Fig. I describe, but with two parallel electrode pairs (5) and (4). In this design, the fill level is generally detected via electrode pair (5). As soon as these electrodes (5) become coated with electrically insulating substances (oil, grease, etc.) from below, the fill level in the dosing vessel (10) will continue to rise until the liquid is detected by the conductivity measurement through the electrodes (5). As soon as this fill level reaches the electrode pair (4), the controller (1) can recognize that a contamination problem exists. A warning message can then be issued, or the dispensing program can be aborted.

[0013] Fig. V shows a sampling device according to the invention as in Fig. III, but with only one electrode pair (5) and one additional electrode (4). The function is the same as in Fig. III described, however, one of the electrodes (5) is the common electrode, via which the conductivity is measured in relation to the other electrode (5) and the conductivity is measured in relation to the electrode (4).

[0014] Fig. VI shows a sampling device according to the invention as in Fig. III describes, but with only one electrode pair (5) and instead of the electrode (4) with a float switch located at the top. The function is the same as in Fig. III described, however, a fault is reported when the float switch (11) detects the fill level instead of the level electrodes (5).

[0015] Fig. VII shows a sampling device according to the invention as in Fig. V describes, but with only one electrode pair (5) and instead of electrode (4) with a capacitive sensor positioned on top. The function is the same as in Fig.III described, however, a fault is reported when the capacitive sensor (11) detects the fill level instead of the level electrodes (5).

Claims

[1] Conductive level detection in a dosing unit of an automatic liquid sampling device with vacuum suction, characterized byThis dosing unit contains two pairs of electrodes that detect the liquid level by measuring the electrical conductivity of each pair as soon as the liquid level reaches the electrodes. One pair of electrodes is aligned parallel to the other conically, so that the measured conductivity values ​​differ more and more as the liquid level in the dosing unit increases. With appropriate control, the liquid level in the dosing unit can be detected, which is particularly suitable for detecting that the electrode pairs are contaminated with, for example, oil or grease. This contamination shifts the detection of the liquid level via electrical conductivity measurement upwards depending on the insulating coating on the electrodes. [2] Conductive level detection in a dosing unit according to claim 1, characterized by, that the dosing unit contains a parallel-aligned pair of electrodes and only one conically aligned electrode, with one of the parallel electrodes being used for measuring the conductivity value together with the other parallel and conically installed electrodes. [3] Conductive level detection in a dosing unit according to claim 1, characterized by , that the dosing unit contains two parallel pairs of electrodes, one pair being longer than the other, so that it can be detected when the longer pair of electrodes can no longer detect the fill level due to contamination, and thus the fill level in the dosing vessel rises so high that the second, shorter pair of electrodes can detect the fill level. [4] Conductive level detection in a dosing unit according to claim 3, characterized by, that the dosing unit contains three parallel electrodes, one pair of electrodes being longer than the third electrode, so that it can be detected when the longer pair of electrodes can no longer detect the fill level due to contamination, and thus the fill level in the dosing vessel rises so high that the third, shorter electrode together with one of the long electrodes detects the fill level. [5] Conductive level detection in a dosing unit according to claim 3, characterized by , that the dosing unit contains a parallel-aligned pair of electrodes and a float switch located at the top, so that it can be detected when the longer pair of electrodes can no longer detect the fill level due to contamination, and thus the fill level in the dosing vessel rises so high that the float switch at the top detects the fill level. [6] Conductive level detection in a dosing unit according to claim 5, characterized by , that the dosing unit contains a parallel-aligned pair of electrodes and a capacitive sensor located at the top, so that it can be detected when the longer pair of electrodes can no longer detect the fill level due to contamination, and thus the fill level in the dosing vessel rises so high that the capacitive sensor at the top detects the fill level.

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