EP3170920A1

EP3170920A1 - Method to control the functioning of a heating apparatus

Info

Publication number: EP3170920A1
Application number: EP16201549.9A
Authority: EP
Inventors: Eros Visentin
Original assignee: Emmeti SpA
Current assignee: Emmeti SpA
Priority date: 2013-03-08
Filing date: 2014-03-07
Publication date: 2017-05-24
Anticipated expiration: 2034-03-07
Also published as: WO2014136097A1; CN107686991B; CN105189822A; ITUD20130035A1; EP2964809B1; CN107686991A; PL3170920T3; EP2964809A1; CN105189822B; EP3170920B1; ES2752849T3; ES2622057T3; PL2964809T3

Abstract

Method to control the functioning of a heating apparatus (10), which comprises a tank (12) for containing an electrolytic solution, an electrode (13) immersed in the electrolytic solution, an electric energy generator (14) connected to the electrode (13) and to the tank (12), and a controller (16) provided with a measurer (15) which measures at least one electric quantity which is established between the electrode (13) and the tank (12). The method provides to regulate the electric energy generator (14) to maintain in the electrolytic solution a protection potential (Vp) suitable to guarantee the protection of the tank (12) from corrosion, and comprises at least a step of detecting electric dispersions present in the tank (12) during which the measurer (15) measures at least one electric quantity, and the controller (16) processes the at least one electric quantity to determine the presence of the electric dispersions.

Description

FIELD OF THE INVENTION

The present invention concerns a method to control the functioning of a heating apparatus, which is advantageously used to reduce phenomena of corrosion connected to the continued use of said apparatus.
In particular, the method according to the present invention can be implemented in a heating apparatus that comprises electric cathodic protection devices against the corrosion of containers, tanks or metal parts containing water, such as for example boilers.

BACKGROUND OF THE INVENTION

Devices are known, for the cathodic protection of heating apparatuses against corrosion, applicable to boilers or water-heaters.
In particular, a boiler-type apparatus is known for heating water, in which an electrode, also called anode, made for example of titanium, is immersed in the water contained in the boiler. An electric energy generator is connected with the positive pole to the anode and with the negative pole to the boiler to be protected from corrosion.
The current that is established between the anode and the boiler is periodically varied over time, in its intensity, for a determinate interval, with respect to the normal operating value and, during this variation, the difference in potential that is established between the two poles of the generator is measured.
The difference in potential measured is compared with a predetermined reference value, corresponding to a known value at which corrosion is impeded; any deviation with respect to this reference value is used to determine a current intensity to be applied between anode and boiler in order to obtain a difference in potential substantially equal to the predetermined reference value.
The known difference in potential value, hereafter referred to as protection potential, is determined in a known manner for example with reference to the Pourbaix diagram, or potential/pH diagram, which is a representation of the possible stable conditions at balance of an electrochemical system in aqueous solution. This model is used to predict the behavior of a metal material regarding corrosion, in this case referred to iron alloys but also applicable for other metals, although with the adoption of different potentials.
Knowing the material that the boiler is made of, it is therefore possible to determine the protection potential to be applied between anode and boiler.
This method of protection, although it guarantees adequate protection against corrosion in the boiler, is a system that is closed upon itself, and is not able to detect possible influences due to factors outside the heating apparatus, such as for example electrostatic loads, electric dispersions or other.
The prior art documents WO 2009/0292987 A1 , WO 2007/010335 A2 and US 6.080.973 A describe systems to control corrosion and/or other functioning anomalies for water tanks and heaters.
One purpose of the present invention is to perfect a method to control the functioning of a heating apparatus that is efficient and that allows to increase the working life of the heating apparatus in which it is applied.
Another purpose of the present invention is to perfect a method that increases the safety of the heating apparatus.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.
In accordance with the above purposes, a method according to the present invention is applied to control the functioning of a heating apparatus in which the heating apparatus comprises:

a tank containing an electrolytic solution, for example water,
an electrode immersed in the electrolytic solution,
an electric energy generator connected to the electrode and to the tank,
a controller provided with a measurer which measures at least one electric quantity which is established between the electrode and the tank.

The method provides to regulate the electric energy generator so as to keep in the electrolytic solution a protection potential having a first known value, substantially constant over time, suitable to guarantee the tank is protected from corrosion.
According to one aspect of the present invention, the method comprises a step of detecting electric dispersions present in the tank, during which the measurer measures at least one electric quantity and the controller processes the at least one electric quantity in order to determine the presence of electric dispersions, which are to be avoided since they are the cause of the corrosive effect generated on the walls of the tank.
According to a first form of embodiment of the present invention, the detection step provides to detect direct currents of electric dispersion present in the tank. According to this form of embodiment, the direct currents detection step comprises:

a step of temporary interruption or reduction of the electric energy supplied by the electric energy generator;
a step of measuring the residual potential, having a second value, which is established between the electrode and the tank;
a step of comparing the second value of the residual potential measured and a third value of a reference potential;

The present invention also concerns an electric cathodic protection device to be associated with a heating apparatus comprising a tank containing an electrolytic solution. The device comprises an electrode immersed during use in the electrolytic solution, an electric energy generator connected to the electrode and, during use, to the tank, and a controller provided with a measurer configured to measure an electric quantity which is established between the electrode and the tank. According to one feature of the invention, the controller comprises a processing unit configured to receive the data of the electric quantity detected by the measurer and to process the electric quantity in order to determine the presence of electric dispersions. The device also comprises indicators associated to the controller in order to indicate the presence of electric dispersions.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

fig. 1 is a schematic representation of a heating apparatus that uses a control method according to the present invention;
fig. 2a is a graph showing the development of potential over time that is applied to the heating apparatus during normal functioning, according to a first form of embodiment;
fig. 2b is a graph showing the difference of potential over time that is measured in the heating apparatus according to the first form of embodiment;
fig. 3a is a graph showing the development of potential over time that is applied to the heating apparatus during normal functioning, according to a second form of embodiment that is not part of the present invention;
fig. 3b is a graph showing the development of electric currents over time, which is detected in the heating apparatus according to the second form of embodiment and in a functioning condition;
fig. 3c is a graph showing the development of electric currents over time, which is detected in the heating apparatus according to the second form of embodiment and in another functioning condition.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications.

DETAILED DESCRIPTION OF SOME FORMS OF EMBODIMENT

A heating apparatus according to the present invention is indicated in its entirety by the reference number 10 and comprises an electric cathodic protection device 11 against corrosion.
In particular, the heating apparatus 10 comprises a tank 12 having a metal surface in contact with an electrolytic solution, such as water.
The electric cathodic protection device 11 in turn comprises an electrode 13 or anode, an electric energy generator 14 and a controller 16.
The electrode 13 can comprise a titanium bar, possibly activated with noble materials.
One form of embodiment of the present invention provides that the electric energy generator is a generator controlled in direct current, indicated hereafter as current generator 14.
The current generator 14 is in turn connected to the controller 16 which controls and manages the functioning of the current generator 14, and possibly signals particular functioning conditions of the heating apparatus 10, like the presence of electric dispersions.
More specifically, the controller 16 is provided with a measurer 15 that measures at least one electric quantity, configured to detect, for example, the values of current or electric voltage that are established in the electric cathodic protection device 11, in this case between the electrode 13 and the tank 12.
The measurer 15 can be a voltmeter, an amperometer, a wattmeter or simply a device to compare at least one of the electric quantities that are to be detected.
Some forms of embodiment provide that the controller 16 comprises a processing unit 19, provided to process the data detected by the measurer 15 and to signal possible anomalous functioning conditions due to the presence of electric dispersions.
To this purpose, the controller 16 can be associated to indicators 17, for example luminous indicators, each of which identifies a functioning condition of the heating apparatus 10.
In order to guarantee adequate protection against corrosion of the tank 12, during normal functioning of the heating apparatus 10, the current generator 14 maintains, between the electrode 13 and the tank 12, a protection potential that is substantially constant over time, indicated in fig. 2a as protection potential Vp.
The protection potential Vp is a known value, determined as described above as a function of the material that the tank 12 is made of, and with reference to the Pourbaix diagram.
Merely by way of example, if the tank 12 is made of steel, the protection potential Vp assumes a value comprised between 900mV and 1200mV.
The protection potential Vp to be established in the electrolytic solution can be generated iteratively by regulating the current supplied by the current generator 14 and detecting with the measurer 15 the establishment of electric currents inside the electric cathodic protection device 11.
The detection of electric currents identifies an unstable condition of the potential in the tank 12.
If the measurer 15 detects a considerable deviation in the electric currents with respect to the previous measurement, the controller 16 regulates the current supplied by the current generator 14 to take it to a constant value corresponding to a balanced current. With reference to figs. 2a, 2b, 3a, 3b and 3c, a method is described to control the functioning of the heating apparatus 10 and, in particular, to detect possible electric dispersions, for example stray currents that affect the tank 12 and that can contribute significantly to the corrosion inside it.
The stray currents may be small in entity, and therefore not produce a direct intervention of the electric safety devices, such as circuit breakers normally provided in the electric network.
Although they do not prejudice the overall safety of the electric network or the heating apparatus 10, stray currents are an important factor with regard to the creation of corrosive phenomena.
Such problems occur both with dispersions of direct current and also with dispersions of alternating current.
With reference to figs. 2a and 2b, a first form of embodiment is described of the method according to the present invention, used to detect electric dispersions in direct current.
During the normal functioning of the heating apparatus 10, the controller 16 regulates the current supplied by the current generator 14, as described above, to maintain a balanced condition of the protection potential Vp between the electrode 13 and the tank 12.
There then follows a step to detect electric dispersions during which a controlled variation of the electric energy supplied by the current generator is provided.
As shown in fig. 2a, the detection step occurs for an interval of time T shorter than the overall functioning time of the heating apparatus 10 according to the invention. Merely by way of example, it may be provided that the time interval T lasts about one minute and is executed with a cyclicity of twelve hours, that is, the detection is performed periodically twice a day.
Some forms of embodiment provide that, during the detection step, the supply of electric current to the current generator 14 is temporarily interrupted, and a measurement is made by the measurer 15.
It is clear that a temporary interruption of the time interval T, in the normal functioning of the heating apparatus 10, does not influence the protective effect against corrosion normally performed by the heating apparatus 10.
Other forms of embodiment provide only a reduction in the current supplied by the current generator 14, and not an interruption thereof.
During the detection, the measurer 15 detects the difference in potential, indicated hereafter as measured potential Vm. The measured potential Vm corresponds to the residual potential that is established between the electrode 13 and the tank 12.
From experiment analysis, Applicant has found that, in the absence of electric dispersions, the measured potential Vm or residual potential quickly moves to an asymptotic value substantially stable over time, as shown in fig. 2b, similarly to the curve in which the measured potential Vm1 is detected.
If there are electric dispersions in the heating apparatus 10, it should be noted that the development of the measured potential Vm, instead of moving to an asymptotic potential over time, rapidly decreases, consequently facilitating corrosive action. This condition is shown by the curve in fig. 2b, in which the potential value Vm2 is detected.
On the basis of these observations, the method according to the present invention provides that the value of measured potential Vm is compared by the controller 16 with a reference potential Vr. Merely by way of example, the reference potential Vr is comprised between 20% and 40% of the protection potential Vp.
If the measured potential Vm is greater than the reference potential Vr, the controller 16 recognizes a functioning condition within the norm. To this end, in fig. 2b, the measured potential is indicated as Vm1 and it can be seen that Vm1>Vr.
If the measured potential Vm is less than the reference potential Vr, the controller 16 recognizes the presence of harmful electric dispersions in the tank 12 and commands the activation of the indicators 17. In this condition, in fig. 2b the measured potential is indicated as Vm2 and it can be seen that Vm2<Vr.
One form of embodiment of the present invention provides that the potential is measured after a period of time S from the moment when the controlled variation of the protection potential Vp is commanded. The period of time S is evaluated, using theoretical experiments, also in relation to the stabilization time of the potential to move to the asymptotic value as described above.
One form of embodiment of the present invention provides that the period of time S is comprised between 30secs and 60secs. The period of time S, before measuring, prevents the detection of transitory effects and allows to temporarily stabilize the functioning of the heating apparatus 10.

Example

Value of the protection potential maintained during normal functioning of the heating apparatus 10, Vp = -1000mV;
Value of the measured potential Vm, 60secs after the temporary interruption of the current generator 14, without direct current dispersions: Vm1 = -750mV;
Value of the measured potential Vm, 60secs after the temporary interruption of the current generator 14, in the presence of direct current dispersions: Vm2 = - 290mV.

Once the measured potential Vm has been measured, that is, after time interval T (fig. 2a), the heating apparatus 10 resume normal functioning, returning the difference in potential to the value of protection potential Vp.
With reference to figs. 3a, 3b and 3c, another form of embodiment of the method that is not part of the present invention is described, used to detect electric dispersions in alternating current.
During the normal functioning of the heating apparatus 10, the controller 16 commands the current generator 14 to generate, between the electrode 13 and the tank 12, a difference in potential with a desired development and variable over time.
In particular, the current generator 14 alternates in very short times, that is, about every 200µs, the generation of a first potential V1, and a second potential V2 with a reduced intensity compared to the first potential V1.
The values of the first potential V1 and the second potential V2 are determined so as to obtain a polarization of the electrolytic solution to a value corresponding to the protection potential Vp.
Some forms of embodiment provide that the second potential V2 is comprised between 30% and 70% of the first potential V1.
The variation in potential between the first potential V1 and the second potential V2 can occur with a square wave development of period P which can be for example about 200µs (fig. 3a).
In the normal functioning of the heating apparatus 10 and in the absence of electric dispersions due to alternating currents, the controller 16 acts by modulating the current to be supplied to the current generator 14 so as to guarantee said protection potential Vp in the electrolytic solution.
During this step, the measurer 15 measures the electric quantities, in this case the current circulating in the electric cathodic protection device 11, to evaluate whether a balanced condition has been reached. The currents measured by the measurer 15 are indicated in figs. 3b and 3c, by Im.
The balanced condition is represented by the consecutive detection of measured currents Im substantially uniform over time (fig. 3b).
The measurements are taken by the measurer 15 when the potential at the heads of the current generator 14 assumes the value of said second potential V2.
In the absence of stray currents, therefore, the measured current values Im are not subjected to big deviations, and remain confined in a band of values 18 that vary around a balanced current Ie as represented in fig. 3b.
In the presence of alternating current dispersions, the measurer 15 detects a fluctuation in the measured currents Im which varies with a periodicity near or comparable to that of the alternating currents of electric dispersion.
To this purpose the data detected by the measurer 15 on each occasion are transmitted to the processing unit 19 to reconstruct the development over time of the measured currents Im. The processing unit 19 is able to identify the cyclicity of the values detected which, in the presence of stray alternating currents, vary with a frequency substantially equal to, or a multiple of, the latter, for example with a frequency of 50Hz or 60Hz or multiples thereof.
It is quite clear that to allow a correct acquisition of the cyclicity of the stray currents, the frequency at which the measurements are made must be greater than the frequency of the stray currents.
If the processing unit 19 identifies a cyclical development of the measurements performed as indicated above, it commands the activation of the indicators 17 to signal to the user a condition of anomalous functioning.
Some forms of embodiment of the present invention can provide that the light indicators comprise a plurality of light sources, in this case (fig. 1) a red led 17a, a green led 17b and a yellow led 17c, each of which identifies a particular functioning condition of the heating apparatus 10.
The controller 16 described above can also provide a function of counting the working time of the electric cathodic protection device 11.
For example, it may provide that in the first electric feed to the heating apparatus 10, the indicators 17 indicate to the user said working time, for example an indication of the years of work that corresponds to the number of flashes of the red led 17a, and an indication of the months of work that corresponds to the number of flashes of the green led 17b. To this purpose it may be provided that the controller 16 also comprises timer means to determine the working time.
In the normal functioning of the heating apparatus 10, and if no electric dispersions are detected, the green led 17b remains switched on.
If electric dispersions are detected, the yellow led 17c switches on and remains on until a maintenance operation is requested.
The red led 17a can be used to indicate conditions of excessive electric absorption by the heating apparatus 10, or to indicate short circuit conditions or an open circuit in the heating apparatus 10.
It is clear that modifications and/or additions of parts may be made to the method to control the functioning of a heating apparatus as described heretofore, without departing from the field and scope of the present invention.
It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of method to control the functioning of a heating apparatus, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

Method to control the functioning of a heating apparatus (10) which comprises a tank (12) containing an electrolytic solution inside it, an electrode (13) immersed in said electrolytic solution, an electric energy generator (14) connected to said electrode (13) and to said tank (12), and a controller (16) provided with a measurer (15) which measures at least one electric quantity which is established between said electrode (13) and said tank (12), said method providing at least a protective step in which said electric energy generator (14) is regulated to maintain, between said electrode (13) and said tank (12), a protection potential with a first value (Vp), known and substantially constant over time, suitable to guarantee the protection of said tank (12) from corrosion, said protection step providing a regulation of a current supplied by the electric energy generator (14), a detection, with said measurer (15), of electric currents established, and a regulation of the current supplied by the electric energy generator (14) to maintain a balanced condition of said protection potential to said first value (Vp), characterized in that it comprises at least a step of detecting direct currents of electric dispersions present in said tank (12), wherein said detection step comprises:
- a step of temporary interruption or reduction of the electric energy supplied by said electric energy generator (14);

- a step of measuring the residual potential, having a second value (Vm), which is established between said electrode (13) and said tank (12), said step of measuring the residual potential being performed during said step of temporary interruption or reduction of the electric energy;

- a step of comparing said second value (Vm) of the residual potential measured and a third value (Vr) of a reference potential;
wherein, if said second value measured (Vm) is greater than said third value (Vr) of the reference potential, said controller (16) recognizes a functioning condition that is within the norm, and wherein, if said second value measured (Vm) is less than said third value (Vr) of the reference potential, said controller (16) recognizes the presence of electric dispersions deriving from direct currents in said tank (12).
Method as in claim 1, characterized in that, if said second value (Vm) of the potential measured is less than the reference potential (Vr), indicators (17) are activated to warn of the presence of electric dispersions.
Method as in claim 1 or 2, characterized in that said third value (Vr) of the reference potential is comprised between 20% and 40% of said first value (Vp) of the protection potential.
Method as in any claim hereinbefore, characterized in that said interruption or reduction of electric energy supplied by said electric energy generator (14) has a duration of an interval of time (T), and in that the detection of the second value (Vm) of said measured potential occurs after a period of time (S) from the start of said interruption or reduction.
Method as in claim 4, characterized in that said period of time (S) is comprised between 30secs and 60secs.
Method as in claim 4, characterized in that after said interval of time (T), said protection potential is returned to said first value (Vp).