FR3093566A3 - Device suitable for monitoring the level of chlorine in the water flowing through a pipe - Google Patents

Abstract

Device (100) adapted to monitor the level of chlorine in the water flowing through a pipe (7), which has an insert member (1) in the pipe with a cylindrical head (3), the base of which has a circular flat capture surface (4), which carries a chlorine sensor (5) based on the amperometric measurement principle, open cell, the first electrodes associated with the chlorine sensor being arranged in an orderly manner on said contacting capture surface with water, said first electrodes comprising a working electrode (5w). The same head of the device also carries a flowmeter sensor (6), diametrically arranged relative to the working electrode of the chlorine sensor, capable of generating a magnetic field perpendicular to the capture surface, of the second electrodes (6a, 6b). being associated with the flowmeter sensor for measuring a potential difference also arranged in said capture surface. Figure to be published with the abstract: Fig. 1

Description

Device adapted to monitor the level of chlorine in water flowing through a pipe

Technical field of the invention

The present invention relates to a device for measuring a chemical product in a fluid stream which circulates through a pipe. The invention is particularly suitable for monitoring the residual level of inorganic chlorine in a drinking water distribution pipe, for which the device is equipped with a chlorine sensor based on the principle of amperometric measurement.

State of the art of the invention

The principle of amperometric measurement is based on the electrochemical oxidation or reduction of certain chemical species on the surface of appropriate electrodes immersed in the solutions tested. The oxidation or reduction reaction involves the transfer of electrons between the chemical species and the electrode, thereby inducing a current flow. Through a selection of the applied potential, the particular species to be measured can also be selected.

In the case of a measurement of free chlorine in a flow of water, the reaction which is favored is the following:

As can be deduced from the previous reaction, the intensity of the current is proportional to the quantity of hypochlorous acid present in the solution.

It is however true that the maximum current for the reaction to occur with the applied potential selected for the amperometric measurement of the component of interest is related to the concentration at a fixed fluid velocity.

Therefore, a problem with sensors based on the amperometric measurement principle is that the measurement is not independent of the flow.

This implies having to ensure a fixed flow as it passes through the sensor. For this purpose, it is common practice to install chlorine sensors based on the amperometric principle in the branch branches of the main pipe, i.e. the pipe through which the feed water flows, the branch being equipped with means to ensure a constant flow of fluid through the sensor and without the possibility of the formation of air bubbles in the measurement environment.

A first object of the invention is a device which overcomes this drawback, which being provided with an insertion member equipped with the flow sensor can be immersed directly in the supply pipe without having to take express measures so that in the environment of influence of the sensor the flow must be fixed.

We know from patent document US 4033830 a compensated flow amperometric analysis system, suitable for measuring free chlorine in a drinking water supply pipe. The system includes the use of a flow sensor to measure the water flow in the influencing environment of the amperometric sensor electrodes to obtain a chlorine measurement compensated according to the flow measurement obtained. The compensation technique is known per se and is essentially based on experience curves and on the calibration of the amperometric sensor in situ, before it is operational. The experiment shows that the current limitation shows a linear relationship with approximately the cubic root of the hydrodynamic flow velocity.

It is advantageous for the system according to US 4033830 that the flow sensor is based on electromagnetic measurement.

Electromagnetic flowmeters are based on Faraday's Law of Induction and are ideal for measuring liquids in drinking water, waste water or any electrically conductive liquid applications and applications that require low pressure loss. charging and low maintenance.

The passage of an electrically conductive liquid through a magnetic field perpendicular to the direction of circulation of the liquid induces an electric voltage V, which is proportional to the speed of the liquid.

The implementation of the system according to US 4033830 however requires the connection of the main pipe to a pipe sector which incorporates several electrodes and inductors, associated with the electromagnetic flowmeter and the amperometric sensor. The system is therefore not suitable for measurement in existing pipes and, in any case, it would require cutting off the water supply to install the system, i.e. to incorporate a section equipped with the sensors chlorine and flow in the supply line.

We know from patent document EP 2656065, a device which could be adapted to measure the free chlorine in a flow of water by inserting a test piece into the water supply pipe, the test piece being equipped with an amperometric sensor and the device being prepared to carry out a measurement with flow compensation. The device would therefore be suitable for measuring existing pipes because it does not require the connection of a section of pipe equipped with electrodes and/or other sensor means.

However, the specimen in EP 2656065 includes a mechanical type flowmeter, which uses a turbine to measure the water flow around the electrodes which provide the chlorine measurement based on the amperometric technique.

This solution is complex, bulky and also not very versatile, it is not suitable for small diameter pipes, for example, of the order of 65 mm in diameter. In addition, the effect of the turbine to measure the flow generates turbulence in the water which negatively alters the accuracy of the measurement taken by the chlorine sensor. Therefore, the measurement obtained does not have the desired precision.

The objective of the present invention is therefore a device which solves all these drawbacks.

Explanation of the invention

The device described is a device suitable for monitoring the level of chlorine in water circulating through a pipe. Said device has a pipe insertion member with a cylindrical head, the base of which has a circular flat capture surface, which carries a chlorine sensor based on the principle of amperometric measurement, with an open cell, of the first electrodes associated with the sensor of chlorine being arranged in an orderly fashion on said capture surface in contact with water, said first electrodes comprising a working electrode.

The device is essentially characterized in that the same head also carries a flow sensor and that it is based on electromagnetic measurement.

With this combination, the inventors have overcome certain prejudices established in the art.

First, by selecting an open cell, membraneless chlorine sensor that allows selective diffusion of HOCl molecules to the sensor; secondly, by arranging in the same head a chlorine sensor based on the principle of amperometric measurement and a flow sensor, also called flowmeter sensor, based on electromagnetic measurement, which, among other things, suggests that there will be a interference between the sensors due to their proximity.

In the device of the invention, the flowmeter sensor is arranged diametrically with respect to the working electrode of the chlorine sensor and is capable of generating a magnetic field perpendicular to the capture surface and therefore perpendicular to the direction of flow which flows through the pipe when the head is correctly inserted in the pipe so that the capture surface is oriented parallel to the flow, second electrodes associated with the flow meter sensor for measuring a potential difference also being arranged in said capture surface in galvanic contact with water and on the theoretical plane in which the magnetic field generated by the inductor fits.

This diametrically opposed arrangement is designed so that the chlorine sensor and the flow meter sensor are aligned with the direction in which the flow or flow of water travels through the pipe. This flow will therefore flow first through the zone of influence of one of the sensors and then through the zone of influence of the other of the sensors. Although the purpose of this measurement is for the fluid velocity to be the same as it passes through both sensors, necessary to perform compensated flow amperometric analysis, this same measurement may conflict with other effects at avoid, such as the micro-turbulences or the alterations that the first sensor against which the fluid collides causes in the latter and which can affect the measurements of the second sensor arranged downstream.

The tests carried out revealed that the layout of the first group of electrodes affected the accuracy and quality of the measurements obtained.

Thus, according to a variant of the invention, the imaginary diametral straight line (D) on which said working electrode of the chlorine sensor is arranged determines a plane of symmetry on the capture surface, the first electrodes of the chlorine sensor and the second electrodes of the flowmeter sensor being distributed symmetrically with respect to said diametral line.

Preferably, the first sensors associated with the chlorine sensor comprise the working electrode, a reference electrode, also coinciding with the diametral line (D) and arranged between the working electrode of the chlorine sensor and the flow meter sensor, a against electrode, on a first side of the diametral line (D), and a grounding electrode, on the other side of the diametral line (D).

More preferably, the reference electrodes, the counter electrode and the grounding electrode of the chlorine sensor are arranged forming an equilateral triangle between them, the working electrode being located in the center.

This particular arrangement places the chlorine sensor counter-electrode as far away as possible from the flowmeter sensor, reducing the effect of variable voltage on the flowmeter sensor. The arrangement of the reference electrode on the diametral line (D) contributes to this, which produces a screen effect.

According to a characteristic of interest, the capture surface is formed, centered, at the distal end of the head, around which there is a beveled annular surface connected to the sides of the head, to attenuate the turbulence generated by the flow when said head is interposed in its path. The bevel can be oriented at 45° to the capture plane.

According to an embodiment of interest, the working electrode of the chlorine sensor is located in elevation, with respect to the capture surface, at a level above the rest of the first electrodes associated with the chlorine sensor. Surprisingly, this measure considerably increases the precision of the measurements. In the working electrode, where the reduction of the chlorine analyte is carried out, the velocity of the fluid has been estimated to be different from that of the fluid as it passes through the flowmeter sensor and it is plausible that the interposition of the The reference electrode, which makes it possible to overcome disadvantages of another nature, is not ideal for avoiding this circumstance. Raising the working electrode eliminates this problem by improving the velocity difference between the sensors.

In the embodiments of interest, the working electrode of the chlorine sensor is raised at a distance h1 between 1.5 and 2.5 mm from the capture surface.

In the embodiments of interest, the working electrode of the chlorine sensor is separated at a distance d1 from the line that connects the second electrodes of the flow meter sensor; and the aforementioned second electrodes of the flowmeter sensor are separated from each other at a distance d2, respecting the ratios 15.75 mm <d1 <17.75 mm; and 14mm < d2 <16mm.

This particular selection gives rise to a sufficiently compact head for the device of the invention to be used in pipes of approximately 65 mm in diameter. In particular, this particular selection proves to be optimal so that the device of the invention can be used in pipes with a diameter of between 65 mm and 150 mm.

According to one embodiment, the flowmeter sensor comprises an auxiliary earthing electrode, arranged equidistant between the second electrodes of the flowmeter sensor and whose contact surface with the water is raised to a distance h2 with respect to the surface of capture.

Preferably, the distance value h2 is approximately half the distance d1 which separates the working electrode of the chlorine sensor from the line which connects the second electrodes of the flowmeter sensor.

In order to be able to install the device for the correct measurement, provision is made to equip the device with an adapter that can be hydraulically connected to a normal service pipe to a water supply pipe, said adapter being tubular and dimensioned to receive the inserter with adjustment inside, the adapter and the inserter being provided with complementary means for the sealed coupling but with a capacity for axial movement of the inserter relative to the adapter.

In a variant, the complementary means for coupling the adapter and the insertion member comprise a rack on the insertion member and a rotating ring on the internal threaded adapter with a pitch corresponding to the internal toothing of the rack.

The invention also provides for the adapter to be provided with an inner seating for movement of the insertion member and with a purge outlet at its lower end, below the level of said inner seating.

is a general view of an insertion member of a device according to the invention;

is an exploded view of the insertion member of FIG. 1;

is a plan and head view of the inserter;

is a perspective and head view of the inserter and

is a partial cross-sectional view of a device according to the invention in the mounting position in a water supply pipe.

Detailed description of the invention

Next, a device which illustrates the invention is described.

This device has an insertion member 1 shown in Figs. 1 and 2. The insertion member 1 is generally cylindrical in configuration and comprises a head 3 whose base has a circular flat capture surface 4.

The head 3 carries a chlorine sensor 5 based on the principle of amperometric measurement, with open cell, and a flowmeter sensor 6 based on electromagnetic measurement.

Sensors 5 and 6 are adaptations of commercial sensors. More precisely, the chlorine sensor 5 is an adaptation of an available sensor ITC© Cl2 Sensor 420 MB; and the flowmeter sensor 7 is an adaptation of a Tecfluid© sensor from the FLOMAT series.

The insertion member 1 is in the example formed of three bodies which can be coupled in a sealed manner and which are nested or coupled successively. An upper body 1c, an intermediate body 1b and a lower body 1a, which determines the head 3 of the insertion member. However, the lower body 1a has a very small diameter of approximately 39 mm, which makes the insertion member 1 suitable for use in a pipe of small diameter, 65 mm, the body 1b being able to accommodate the entire electronics required by the sensors. The space offered by the lower body 1a is also adequate to house the inductor 6i of the flowmeter sensor based on the electromagnetic measurement.

The dimensions of the insertion member 1, and in particular of its lower body 1a, make it a priori complicated to mount on the same head 3 a chlorine sensor 5 based on the principle of amperometric measurement, with an open cell, and a flowmeter sensor 6 based on electromagnetic measurement because the two will be arranged very close to each other causing an increase in the noise of the signals which negatively affects the measurement of the flowmeter sensor.

The particular arrangement of the essential elements of the sensors, however, makes it possible to overcome this obstacle in an unpredictable way at the start.

Figs. 3 and 4 show the head 3 of the insertion member 1 in detail. From these figures, it can be seen that the base of the head 3 has a circular flat capture surface 4 and that the chlorine sensor and the flowmeter sensor 5 and 6 are diametrically arranged there.

More specifically, in the exemplary implementation of the invention, the first sensors associated with the chlorine sensor 5 comprise a working electrode 5w, a reference electrode 5r, a counter-electrode 5c and a grounding electrode. land 5m.

The aforementioned capture surface 4 is formed, centered, at the distal end of the head 3, around which there is a beveled annular surface 4a connected to the sides of the head, in the example at 45° , to attenuate the turbulence generated by the flow when said head 3 is interposed in its path.

In the implementation example, for its part, the flowmeter sensor 6 comprises in a manner known per se an inductor (not shown) capable of generating a magnetic field perpendicular to the capture surface 4 and therefore perpendicular to the direction of flow which circulates through the pipe when the head 3 is correctly inserted into the pipe 7 (see Fig. 5) so that the capture surface 4 is oriented parallel to the flow. Second electrodes 6a, 6b associated with flow meter sensor 6 for measuring a potential difference also arranged in said capture surface 4 in galvanic contact with the water are located on the theoretical plane in which the magnetic field generated by the inductor.

It should be noted that the imaginary diametral line (D) on which said working electrode 5w of the chlorine sensor 5 is arranged determines a plane of symmetry on the capture surface 4, the first electrodes of the chlorine sensor and the second electrodes of the flowmeter sensor 6a, 6b being distributed symmetrically with respect to said diametral line. In the example, the reference electrode 5r of the chlorine sensor 5 is located coinciding with this diametral line (D) and arranged between the working electrode 5w of the chlorine sensor 5 and the flowmeter sensor 6; and the reference electrodes 5r, the counter electrode 5c and the grounding electrode 5m of the chlorine sensor 5 are arranged forming an equilateral triangle between them, the working electrode 5w being located in the center.

Fig. 4 also shows another characteristic of interest, namely that the working electrode 5w of the chlorine sensor 5 is located in elevation, with respect to the capture surface 4, at a higher level than the rest of the first electrodes associated with the sensor of chlorine 5.

In the example, a set of ratios and proportions are respected to optimize the quality of the measurements obtained. Thus, the working electrode 5w of the chlorine sensor 5 is raised at a distance h1 of 2 mm from the capture surface 4; the working electrode 5w of the chlorine sensor 5 is separated at a distance d1 of 16.75 mm from the line which connects the second electrodes 6a, 6b of the flowmeter sensor 6; and the aforementioned second electrodes 6a, 6b of the flow sensor 6 are separated from each other at a distance d2 of 15 mm.

Figs. 3 and 4 also show that the flowmeter sensor 6 used in the example comprises an auxiliary earthing electrode 6c, arranged equidistant between the second electrodes 6a, 6b of the flow sensor 6 and whose contact surface with the the water is raised to a distance h2 with respect to the capture surface 4. The value of the distance h2 is approximately half the distance d1 which separates the working electrode 5w from the chlorine sensor 5 from the straight line which connects the second electrodes 6a, 6b of the flowmeter sensor 6. In the example, this distance h2 is 8.5 mm.

As in the initial flowmeter sensor, the passage of an electrically conductive liquid, for example water from a supply network, through the magnetic field perpendicular to the direction of circulation of the liquid induces an electric voltage V, which is proportional to the velocity of the liquid. The second electrodes 6a and 6b in contact with the liquid pick up this voltage V, respecting the ratio

V=B・v・d

Where V is the voltage measured across the electrodes; B is the magnetic field density; v is the velocity of the liquid; and d is the distance between the electrodes.

The flow measurement is used to compensate for the dissolved chlorine measurement in the water. To this end, the electronics of the device 100 integrates processing means to implement this compensation. In the state of the art, there are methods described for this purpose, which relate to the fact that the current limitation shows a linear relationship with approximately the cubic root of the flow velocity. This report is for example found in publications such as, for example, "Water world: amperometric probes or dpd analyzers: which is best for on-line chlorine monitoring?, January 1, 2009 (sponsored by Jim Huntley and Dr. Vadim Malkov ); and “The Science and Technology of Industrial Water Treatment” (edited by Zahid Amjad, section 24.2.2.1 technology limitations).

Device 100 is compatible for situations where electrical power is not available. To this end, the device 100 comprises an energy storage source, in the form, for example, of a battery or a combination of batteries, and programmable electronic means which manage a program for controlling the sensors. Concretely, from the empirical data obtained, the programmable electronic means are able to execute an ignition program that includes a data capture cycle that first produces the ignition of the chlorine sensor 5 for its polarization; then switching on the flowmeter sensor (only when the chlorine sensor 5 is prepared to ensure a good analytical measurement); then the capture of the measurements both by the chlorine sensor 5 and by the flowmeter sensor 6, in which said capture occurs several times in succession during a predetermined time interval and from which the average values to be used in the final calculation will be obtained. As an example only, it is possible to choose to perform the measurements five times at intervals of 1 sec. This gives rise to 5 measurements in 5 sec.

To obtain a good measurement, there are other factors that must be taken into account, one of them being the correct insertion and arrangement of the insertion member 1 in the water flow.

To ensure the proper arrangement of the insertion member 1, the device 100 is equipped with an adapter 101 which can be hydraulically connected to a normal service pipe 7a to a water supply pipe 7, in the example d a commercial valve body.

Said adapter 101 is tubular and is sized to receive the insertion member 1 with adjustment inside, the adapter and the insertion member being provided with complementary means for coupling 102a, 102b sealed, but with a axial movement capacity of the insertion member 1 with respect to the adapter 101, all as illustrated in FIG. 5.

Depending on the pipe diameter, an insertion distance or, similarly, a location of the head 3 of the insertion member for which the flow compensation has been calibrated is optimal. It is envisaged to provide the insertion member, for example, in the visible part of the upper body 1c, with visual indications of insertion levels so that the operator knows what is the ideal relative position between the member of insertion 1 and the adapter 101 (and with it the level of insertion of the head 3), depending on the diameter of the pipe.

In the example, the complementary means for coupling the adapter and the insertion member comprise a rack 102b on the insertion member 1 (see Fig. 1) and a rotating ring 102a on the adapter 101 internally threaded with a pitch corresponding to the internal toothing of the rack. Rotation of the thread in one direction or the other will move the inserter 1 towards its insertion or towards its extraction, respectively, from the conduit 3.

The adapter 101 is provided in the example with an internal seat 103 as a stop for movement of the insertion member 1 and with a purge outlet 104 (or sampling) at its lower end, below the level of said inner seat 103.

Claims (13)

Device (100) suitable for monitoring the level of chlorine in water flowing through a pipe (7), which has an insertion member (1) in the pipe with a cylindrical head (3), the base of which has a circular flat capture surface (4), which carries a chlorine sensor (5) based on the principle of amperometric measurement, with open cell, first electrodes associated with the chlorine sensor being arranged in an orderly fashion on said capture surface in contact with water, said first electrodes comprising a working electrode (5w), the device being characterized in that the same head also carries a flow meter sensor (6) based on electromagnetic measurement, diametrically disposed with respect to the work (5w) of the chlorine sensor (5), capable of generating a magnetic field perpendicular to the capture surface (4) and therefore perpendicular to the direction of flow that circulates through the pipe when the head (3) is correctly t inserted into the pipe (7) so that the capture surface 4 is oriented parallel to the flow, second electrodes (6a, 6b) associated with the flow meter sensor (6) for measuring a potential difference also being arranged in said capture surface (4) in galvanic contact with the water and on the theoretical plane in which the magnetic field generated by the inductor fits. Device (100) according to Claim 1, characterized in that the imaginary diametral line (D) on which the said working electrode (5w) of the chlorine sensor (5) is arranged determines a plane of symmetry on the capture surface (4 ), the first electrodes of the chlorine sensor and the second electrodes of the flowmeter sensor (6a, 6b) being distributed symmetrically with respect to said diametral line. Device (100) according to Claim 2, characterized in that the first sensors associated with the chlorine sensor (5) comprise
- the working electrode (5w),
- a reference electrode (5r), also coinciding with the diametric line (D) and placed between the working electrode (5w) of the chlorine sensor (5) and the flowmeter sensor (6)
- a counter-electrode (5c), on a first side of the diametric line (D), and
- an earthing electrode (5m), on the other side of the diametral line (D). Device (100) according to Claim 3, characterized in that the reference electrodes (5r), the counter-electrode (5c) and the grounding electrode (5m) of the chlorine sensor (5) are arranged in forming between them an equilateral triangle, the working electrode (5w) being located in the center. Device (100) according to any one of the preceding claims, characterized in that the capture surface (4) is formed, centered, at the distal end of the head (3), around which there is an annular surface (4a) bevelled in connection with the sides of the head, to attenuate the turbulence due to the flow when said head (3) is interposed on its trajectory. Device (100) according to any one of the preceding claims, characterized in that the working electrode (5w) of the chlorine sensor (5) is located in elevation, with respect to the capture surface (4), at a level above the rest of the first electrodes associated with the chlorine sensor (5). Device (100) according to the preceding claim, characterized in that the working electrode (5w) of the chlorine sensor (5) is raised to a distance h1 between 1.5 and 2.5 mm from the capture surface (4 ). Device (100) according to the preceding claim, characterized in that the working electrode (5w) of the chlorine sensor (5) is separated at a distance d1 from the straight line which connects the second electrodes (6a, 6b) of the flowmeter sensor ; and in that the aforementioned second electrodes (6a, 6b) of the flowmeter sensor (6) are separated from each other at a distance d2 , the ratios 15.75 mm < d1 < 17.75 mm 14 mm < d2 < 16 mm being respected. Device (100) according to any one of the preceding claims, characterized in that the flowmeter sensor (6) comprises an auxiliary earthing electrode (6c), arranged equidistant between the second electrodes (6a, 6b) of the flowmeter sensor (6) and whose contact surface with the water is raised to a distance h2 with respect to the capture surface (4). Device (100) according to Claims 8 and 9, characterized in that the value of the distance h2 is approximately half the distance d1 which separates the working electrode (5w) from the chlorine sensor (5) from the line which connects the second electrodes (6a, 6b) of the flowmeter sensor (6). Device (100) according to any one of the preceding claims, characterized in that it is equipped with an adapter (101) hydraulically connectable to a normal service pipe (7a) to a water supply line ( 7), said adapter (101) being tubular and dimensioned to receive with adjustment inside the insertion member (1), the adapter and the insertion member being provided with complementary means for the coupling (102a , 102b) sealed but with a capacity for axial movement of the insertion member (1) relative to the adapter (101). Device (100) according to the preceding claim, characterized in that the complementary means for coupling the adapter and the insertion member comprise a rack (102b) on the insertion member (1) and a ring (102a) on the adapter (101) with internal thread with a pitch corresponding to the internal toothing of the rack. Device (100) according to any one of Claims 11 or 12, in which the adapter (101) is provided with an internal seat (103) as a stop for movement of the insertion member (1) and with a drain outlet (104) at its lower end, below the level of said inner seat (103).